making your own live rock??!!!

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ALL OF THIS INFO CAME FROM ANOTHER PAGE!!! i HAVE NOT TESTED ANY OF IT do you guys think it would work ????
Making Your Own Live Rock
May 24, 1998 on #reefs
Greetings fellow rockers and future rockers! It’s time to share some of our joint ideas on making and curing reef-safe cement rocks for aquarium use and for growing some great cement live rock of your own. Some of you have been to scared to try cement rocks (like I was), since cement can have some dangerous qualities. We’ll cover the problems and simple solutions so that you can charge ahead in full confidence when making and using cement rocks.
Why use cement rocks for your aquarium?
Cement rocks are quite easy to make and can be made very cheaply if you know what to use. Some people have just used cheap cement "post mix" to make rocks for freshwater aquariums and even for saltwater aquarium use. Post mix is a dry bagged mix of Portland cement powder, sand and gravel that you just add water to, stir and form it into rocks. However, you may be much safer not using ordinary gravel that is contained in post mixes which may have heavy metals that could dissolve more readily in saltwater. I prefer to use sand and gravel like crushed coral, aragonite sand, dolomite, crushed oyster shell or builders #20 white silica sand. Using either of the latter two will keep your cost of cement rock under 10 cents per lb! You can mix these with any cement powder like type I/II Portland cement which is the easiest to find at places like Home Depot or other builder’s supply stores. Some very nice shapes and custom rock sizes can be made from cement. It is sometimes very hard to find just the right size and shapes of wild live rocks to make the perfect aquascape in your aquariums.
Curing Cement Rocks
Curing your new cement rocks is your next, and biggest, concern. In, I would suggest that you read the article I wrote on making and curing cement rocks, in the May 1998 Marine Fish Monthly. You can also read it on my web site at, http://www.geocities.com/CapeCanaver...ementRock.html . This web site article also has several pictures of cement rocks and information on how to grow good coralline algae on it and other types of rocks. Pictures of how to grow coralline and how "not to" grow coralline are also in this on-line article. If you do not properly or adequately cure your cement rocks before using, you could end up killing everything in your aquarium, if you use enough cement rock to accomplish this "feat". You can add a small cement rock to an aquarium and let it cure right in the aquarium. The key is not to put too large of one in or you cross the line and the pH goes up too far and thing die. New cement rocks will leach heavy amounts of calcium oxide and calcium hydroxide (the two forms of kalkwasser - KW for short). You wouldn’t dump a whole bunch of KW in your tank would you? The other problem is that you can cure your rocks enough to use higher volumes of cement rock in your aquarium, but if you cure the rocks just enough to lower the pH to the point that it will not kill things, you could still end up releasing enough KW into your aquarium that you can precipitate calcium out of the water and clump your aragonite sand substrate! Be sure to cure your cement rocks enough to avoid both of these problems.! So, you need to soak the cement as it cures since more KW is released from cement as it hydrates/cures, and it does take time. Patience is important here.
Quick cures using vinegar or acid will just cost you extra money and do not really "cure" the cement. People have killed their marine life by using these quick cures when using a lot of cement rock at once. Sure, you can get away with using quite small volumes of cement rock with these quick cures, if the amount of KW being leached after the "cure" is not too high for the volume of your aquarium. The quick acid cures lower the pH some, but tend to take just as long or longer to really finish curing after this! The most dramatic part of real curing takes place in the first week, but significant hydrating (curing) still takes place for at least the first month or longer. You can witness this by putting your cement rocks in fresh tap water (after they are about two to seven days old) and doing weekly water changes while testing the pH. Depending on the cement to water ratio that you cure them in, they will leach enough KW into the water in the first week to raise the pH up to maybe 10, 11 or higher! They also leach silicates when they are curing. This doesn’t sound like what you want in your reef aquarium? Don’t let this make you nervous, because once the cement rocks have had ample time to cure, they are leaching virtually no silicates or KW and are VERY reef-safe! You just have to be patient and test the pH of the curing water each week until it comes down below 8 to stay.
Bubbling CO2 through the curing water will lower the pH since the CO2 combines with the KW to make calcium carbonate in the water and inside the rocks. This strengthens the rocks. It is really not necessary to use CO2 though a few people have. You can just use a fine airstone to bubble regular air through the water to put some CO2 into the water and a achieve a similar result. Curing in stagnant water is slightly slower, but has one advantage. You will know when the cement rocks are still leaching KW since you will not be forcing the removal of KW with CO2 and masking the pH. Even if you use an air bubbler while curing, be sure to turn it off for a couple of days when you think the cement is cured so you can tell if KW is building up in the water. A rising pH in stagnant curing water will tell you if your cement is still curing significantly. Curing in plain water is really the easiest and cheapest method and it does take time. We will discuss some possible accelerated curing methods (that really work) later on.
Basically speaking it is best or safest to Give your cement rocks about six weeks of curing time in tap water and then two weeks in saltwater after this, before adding them to your aquarium. I just lost some of you when I said "... then two weeks in saltwater...", right? After you are done curing, and it may be quicker or longer than six weeks (You have to test YOUR curing water pH to see for sure.), you will notice that when you put one of your cured cement rocks in a jug or bucket of stagnant saltwater from your aquarium that the pH raises to about 8.6 or higher by the next day! I call this pH rebound. It can take a couple of extra weeks in saltwater for this pH rebound to subside. I do not know why the rocks start leaching more KW when you put them in saltwater after a freshwater cure. Any suggestions from chemists out there? I’m obviously not one myself.
One more note on curing time. A few factors will affect the curing time of your cement rocks. For starters, small rocks cure quicker. The pH of your tap water can speed or slow curing. My tapwater is about 7.6 to 8.0 ph and is high in calcium, magnesium and other elements that make water "hard". I get quicker curing times in this tapwater than people using soft water or RO water. Soft water with a low pH and with very low amounts of these dissolved solids will actually take longer to cure. Some people have even reported six months of curing in very soft or RO water! I suspect that you might not get the pH rebound with saltwater after a complete curing in RO water, but have not been able to verify this (yet). The longest I have been curing rocks in RO water is since January this year and they are STILL not "totally" cured, but probably close enough to start a "saltwater finish". Actually and technically speaking, cement hydrates or "cures" indefinitely to some insignificant extent. I would guess that you would be safe cutting off your RO water or softwater curing at about six weeks or so, and then add some rock salt and Epsom salts to "harden" up the water and finish off curing. Just be sure the pH is down after the final saltwater finish-off curing is done. You can use about 1/4 cup of cheap rock salt and one TBSP of Epsom salts (MgSO4.7H2O) to make a close-enough half-strength approximation of the major elements of saltwater. I’ve been working on this and so far it looks good. A little extra magnesium from Epsom salts might even help here??? More info on Epsom salt curing later.

 

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James Wiseman suggested using cement with silica fume mixed into it to drop the cement’s pH and strengthen the cement. Gerwick Company, that James works for, uses this type of cement mix for actual "in-ocean" reef structure repair work. You can get more info on this from the article on my web site, referenced earlier. There is also a link in my article to the on-line Gerwick Newsletter with an article on their cement reef repair work. I do get quicker curing when using silica fume but it is harder to find and it is not too cheap. I seem to be able to cure these silica fume rocks at least one or two weeks faster, and the initial curing pH does not go nearly as high either. If you make a whole lot of fancy delicate shaped rock structures, it might be worth looking into. This might raise my costs for making a whole lot of stronger faster curing cement rock to a little over 10 cents per lb. A 25 lb bag of silica fume (about $15 - $25) goes a long ways. The 25 lb bag has five smaller five pound bags inside of it. I don’t think you can buy just one of the sub-five pound bags since the sub-bags are made of dissolvable plastic-like material, maybe gelatin based, so it should be kept dry. Just ONE of these five pound bags is made to go with one 94 lb bag of Portland cement which in turn goes with about 400 lbs +/- of crushed oyster shell or other sands! Want to make a ton of cement rock<g>?
Different materials take longer to cure also. Silica sand cement seems to cure faster, while aragonite cement cures a bit slower and crushed oyster shell cement even a bit slower than that. I still like the oyster shell cement best. It is cheap and has great texture.
Some "Interesting" History of Cement use for Aquariums
Now it’s time for a little bit of cement rock history. Of course everyone sees and tells history differently so it is never "set in concrete". Here is my association with cement and some very general history before that. I am actually VERY new on the marine cement rock scene. I didn’t start making cement rocks until 1996. I had thought about it and then I saw references and pictures of using cement from Delbeek and Sprung’s book "The Reef Aquarium, Vol I", but I was still apprehensive and a bit scared about what to use and properly curing them (not enough info to suite my tastes). Bob Stark of ESV had told me that he had been making and using cement rocks from aragonite sand and from crushed oyster shell, but he said that you had to cure them right or they could kill things in your aquarium. So I waited... Then in the summer of 1996 I heard that GARF had just started experimenting with cement rocks for their reef aquariums. I made my second trip to GARF just after that, in September of 1996, and saw what they were just starting to do with cement rock work. Their first rock made was an arch made of Quick-Crete mix which had recently been place in Sally Jo’s aquarium which had a reef structure made mostly of tank cultured live rock made from ancient Idaho aragonite rocks. The new Quick-Crete arch had just started flaking in one or two spots when I got there to see it. It has continued flaking and crumbling since then. I don’t know what is in Quick-Crete to make it flake in saltwater. The regular cement was working just fine for them though. I then got up the courage to try making cement rocks myself. I opted to use cheap crushed oyster shell for mine, like Bob Stark has suggested. Well, that’s the "not so historical" part of cement rock history<g>!
Bob Stark had been making aragonite cement and crushed oyster shell cement since 1991. ---- Perrin had been making cement reef rocks in the 1980's. He had been very successful also when using silica sand, as mentioned above. Dave Smith of Reef Encrustaceans has also been a long-time cement rock maker, using various materials including aragonite sand. There were also aquarists in Europe making cement reef aquarium rocks in the 1980's (probably earlier too?), and others here and there making cement rocks for reef and saltwater aquariums even earlier. Don’t forget that public aquariums were using cement rock before and after world war II.
I recently looked for other references of early cement rock making and it is sometimes hard to come by, especially references to proper curing. (If you have more "specific" information, I would like to hear about it and possibly add it to my reports) I checked with many sources and one person had some additional information that I thought you might like to hear about. In other words, aquarium cement use goes back even further and we just don’t know who the first person was to use cement rocks in reef aquariums, or other aquariums for that matter. Jake Levi (aquarist of 40 years, professional fish breeder and reef farmer) had used cement rocks years ago in saltwater aquariums and reef aquariums, He also used cement rocks in freshwater aquariums as early as the 1960's. Here’s what Jake had to add:
"In reference to credits for cement based rocks, there were at least three companies that I am aware of back in the 1970's marketing cement based rocks. One of them, Metaframe, marketed a red rock made in ledges and overhangs and caves for building rock ledges and caves and it was extremely popular with the African Cichlid growers back then. Each piece of rock was attractively packaged and they sold a lot of them. One fish farm in Florida sold a Florida sand-based cement rock that was used in both fresh and salt water aquariums, it along with a couple other companies’ products were featured by a pet chain named Pet Bazar out of Toledo Ohio in 119 of their stores. This was all in the mid 1970's. I know of no-one giving these companies credit for their cement rocks even though they were commercially marketing cement rocks over 20 years ago. I think it would be extremely difficult now to trace who was the first to make and sell cement based rocks. In more recent history, ---- Perrin of Tropicorium in Romulus Michigan was making his own cement based rocks back in the 1980's, but began buying calcite reef rocks from CaribSea to save time on rock making. The actual original credit might have to go back into the 1920's and 1930's, as Inness recommended the making of cement rocks for aquariums and pools, in the very first edition of his classic book on aquarium keeping. You might find it in the rare book section of some libraries. This book came out in the late 1920's. I have no doubt that he got the idea from someone else. My own experience with cement rocks is only in the 1960's, making rocks with regular Portland cement and several colored sands to make rocks for building ledges and caves when I was breeding plecostomous, cats and a few of the early African cichlids. I did not try any in saltwater though until the mid 1970's and that was only for a couple of years, and not again until the last few years.
I should tell you about the rock on my bookcase. It is from the seawall of king Herod’s palace on the coast and is a cement mix with coral sand and the seawall protected a pool of corals in the palace garden. I think that makes cement rocks older then most folks here realize. I am NOT claiming it as a Jewish invention.
Actually, the Chinese also made cement, as did the Romans. But Herod’s shore garden is the first instance that I know of using cement in an "aquarium". One other thing, cement aquariums were very popular in the Far East. I even had one once. Mr Lee Chin Eng used some also, a glass front and the rest made of cement." - Jake Levi
Holy crab, Jake! Does that mean that one of the earliest reef aquarists was king Herod, 2000 years ago!?

 

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A Simple Cheap Recipe for Making Cement Rocks
Try this good simple basic recipe to make some of the cheapest porous cement reef rock around. It costs only about 9 cents a lb using this recipe. Using a five gallon bucket, add 5 cups of common easy to find type I/II Portland cement from Home Depot, a hardware store or building supply store. Add 20 cups of crushed oyster shell from a farm feed store. Add 5.5 cups of water and mix very thoroughly with a small hand held flower gardening digger. Use rubber gloves to protect your hands from chemical burning due to extended exposure to the high pH of the fresh cement - this is like soaking your hands in supersaturated kalkwasser! Tip the bucket on a 45 degree angle and rotate or roll it to help tumble and mix the cement well. Use a small gardening hand digger to mix the cement as you tumble it in the bucket. If the mix is too dry add a little more water (slowly). Karen Holt, AKA "The Rocker" tries for a final mix with the consistency of cottage cheese. Others go a bit wetter than this, but not too slushy. You can get crushed oyster shell at a farm feed store. It is used as a very common chicken feed supplement. And that, my friend, is why THIS cement reef rock recipe is so "cheep, cheep, cheep"!
Do not make the final product too runny or you will not be able to shape it into nice looking irregular shapes as well. An almost slushy mixture that will still stand up just a little and take some shape (just a bit) is just right for molding in a damp sand bed. In fact, James Wiseman advises that a wetter mix not only assures that the silicates in the cement mix get hydrated and bound, but a slightly wetter mix will produce more micro-pores or capillaries throughout the cement for better bacterial colonization inside the rocks. On the other hand, this can also weaken the cement just a bit, but usually not critically so. Still, don't make it too dry or the cement will have too many large airspace gaps between sand or crushed oyster shell bits and it will then be just as weak or weaker than the mix that is too wet. Maximum hardness (for practical purposes) is mostly reached after about a month of curing. Now, using rubber gloves, scoop handfuls of it into a bed of dampened sand (or substitute, like dampen crushed oyster shell!) for molding and shaping your cement into reef rocks.
Some molding instructions, tips and pictures are found in the above referenced article on my web site. It will help you make some nice cement rock shapes and sculptures, including one that Paul Baldassano of New York has been making since the 1970's. Tips for growing good coralline algae on your cement rocks are also given in that article.
More Cement Curing Ideas
Bob Stark tells me that he cures by using an airstone in fresh water and bubbling the curing water with the cement rocks in it for one week and then he changes the water and adds baking soda and continues bubbling and adding baking soda until the pH comes down, and I don't know how long that is. He stops when the pH comes down below 8.5 which WILL support fish and corals just fine, as long as your tank has good aeration to equal what the airstone you were curing with does. He feels that silicate leaching is also pretty much done by then. My concern is still that with KW leaching and boosting the pH to around 8.4, you could end up binding your aragonite sand when the calcium precipitates form the water and forms calcite in the sand grains. Excess KW dosing can do this even mor easily than buffers, or at least at a lower KH/alkalinity. I still feel much better about taking the pH lower than 8 in stagnant water conditions before adding the cement rocks to an aquarium with aragonite sand. Besides, once you change the fresh water with salt water for a final two week curing, the cement rocks that were previously raising the ph of fresh water to a level of less than 8 pH in four days in stagnant saltwater will now raise the pH of the new saltwater change to over 8.6 or 8.7 in one or two days sitting in stagnant tank water (saltwater). After this final two weeks curing in salt water with an airstone running to form calcium carbonate and lower the pH, you will not get a dramatic rise in pH anymore when you turn off the airpump, which indicates that curing and leaching of KW and silicates are practically done and the rock is safe to use in a well aerated aquarium.
I'm still coming up with additional info and trying for quicker curing methods. You can try using rock salt and Epsom salts in the curing water near this final stage also. I have gotten some good results with it so far, but it could use some more testing to make sure it is a good final cure as it looks so far. I am thinking that two weeks in fresh water with one change each week and then adding rock salt and Epsom salts (MgSO4) and still bubbling could be a good method. I have added baking soda to this also in one current batch curing in a big garbage can. Using a fine airstone will make sure that the CO2 from the air you pump through is getting absorbed in the water better and forming Calcium carbonate in the rocks and in the water and keeping pH depressed.
One cement rock I have been running test on is made from one cup of mixed up oyster shell cement and was cured in one quart of stagnant fresh water (no bubbling at all) until the pH of a new change of water did not rise above 8.9 after two days sitting in his stagnant water. the curing water was left stagnant so as not to mask the leaching of KW by adding CO2 via an airstone which lowers pH and masks the true status of the curing cement rocks. After the pH had dropped to 8.9, then two TBSP of MgSO4 was added (no rock salt or baking soda) to the one quart of new curing water and the rock was left to sit in this stagnant solution. the pH dropped to 8.65 within 24 hours with no more water changes. The pH had dropped to 8.55 after sitting for two more days. I did stir the water briefly for about 10 seconds each day, but not enough to introduce significant CO2. After two more days I bubbled the water gently for one days and the pH dropped to 8.2. I then shut off the air bubbler and let it sit stagnant and the pH dropped to 8.05 within another 5 days. The pH did not change in the next two days so I dumped the curing water with MgSO4 and replaced it with reef tank water to see if the pH would go back up as it so often does after a freshwater curing is done and you put the "cured" cement rocks in saltwater and the pH climbs or rebounds again. The pH did climb from 8.05 to 8.6 withing 24 hours! So, I though that the MgSO4 curing had failed and I just let it set and forgot about it for 5 more days. When I tested the pH this time, it has dropped (with no aeration!) to 8.0! I don't know how soon it dropped back, but it does not do this spike and quick drop-back after just curing in freshwater alone. I need to try it with just the MgSO4 and another batch with MgSO4 and rock salt after the initial curing to 8.9 in freshwater and then into the tank water for a final test and test the pH EVERY day to see if the pH spikes, and if it does, see how long it takes to drop back down.
Dallas Warren had told me that curing cement in salt water could result in some magnesium replacement of calcium in the cement, resulting in weaker cement. I though that the tank water might be the reason that the smaller rocks I had cured solely in reef tanks had cured much faster than any freshwater curing had ever worked for me. Cement is sometimes cured in the ocean, but it is usually mixed with silica fume to make it more resistant to saltwater weakening. I have used silica fume in some rocks with quicker curing results also, even though it makes the rocks much less porous and you would think this would make inner curing go much slower, but it seems not to work that way for some reason??? The rocks cured in my tanks did not seem weaker and seem plenty strong for reef aquarium use. I had no way of truly testing them for PSI strength.
The fastest complete curing I have experienced is 17 days, and that WAS by putting small newer unsoaked cement rocks in reef tanks - small enough rocks that it does not boost the pH of the much larger volume of a reef tank up too much. Its like adding slow release KW since that's what cement leaches as it cures. You don’t want to add too much or you kill fish and everything living in your tank! I have done it and others have done it with fast-cure methods using vinegar and water for a week or two of curing. It works fine fi you don't add much of this rock to your tank and have really good aeration. But you can add these small amounts of completely uncured rocks also, if you don;'t cross the line of no return. I safely used cement rocks containing up to two cups volume in a 55-gallon tank. The Tank's pH climbs a little and the KH too. and then it slows down and drops back as full curing happens. The only problem is that the rocks leach more silicates into your tank than you might care for and you can end up with a brownout of diatom growth with just two cups volume of cement rock in a 55-gallon tank! So, maybe we shouldn't really pursue low volume tank curing after all???

 

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I took a few rocks out of the tanks after 17 days and put them in small containers of stagnant tank water to see how close they really were to being fully cured, and I found that they were done! No pH problems, even in stagnant saltwater! The pH went from 8.2 up to 8.3 by the next day, but dropped back to 8.1 by the following day. I kept adding evaporation replacement water to the curing containers, a milk jug with the top cut off and two large glasses for the smaller rocks, so I could keep monitoring the pH to see if it would slowly go up or maybe even quickly spike. After more than two months of this saltwater soaking, the pH has very slowly dropped to 7.9 pH. I think that the 17 days in a tank was a virtually total cure. I wanted to approximate the amount of tank water to rock that you would put in a typical reef tank for a more true to life pH testing concentration of the cement rock to tank water ratio. I think we may be able to get a 2.5 week cure like this without the silicates leaching in our aquariums, and without the expense of high volumes of higher cost aquarium saltwater mixes to do it. I would suggest that you try concentrating the major elements of saltwater like magnesium (possibly) with cheap substitutes like rock salt (un-iodized) and Epsom salts. I would suggest curing the cement rocks in freshwater for possibly a couple of weeks first, to help the cement gain some initial strength, away from saltwater.
No matter what method you use to cure your cement rocks, be sure to test the rocks in stagnant water for a few days to verify that the pH is not rising dangerously. Bob Stark is now working on another accelerated (and SAFE) method for curing cement rocks. He will pass it on to others and me if it works out. If that comes to pass, I will post an article by Bob, on accelerated cement rock curing, on my web site in the "Raise a Reef" section. I hope to be herring from him soon, so stay tuna’d and I’ll sea you there!
And remember, Rock on!
Tom Miller
When the Rock has cured the PH should be 8.3 or under, correct?
Yes, but you can get away with slightly higher like Bob Stark does, but I prefer below 8, and even 7.5 to 7.7 holding steady in stagnat water for four days or longer (in salt water) for relly cured cement rock.
But, you can get away with just the freshwater cure and make sure you have good aeration to keep the pH down. You will watch the KH in your tank or curing container of saltwater climb if the rock is still leaching.
People do vary it a little, but the aragonite sand can get crystalized a bit with calcite even if it does not clump, so if you like the benefits of aragonite sand buffering and adding calcium, then be cautious on this point of jumping the gun.
Why are oyster shells a great substrate if they are high in phosphate?
They are high in phosphate and have silicates too, but others and I have not had a leaching problem once they are cured in cment.
Has anyone used pearlite in the rock to lower weight, and what possible side effects might it have?
I've heard of it but do not doit.
I can get very light rock and porous too by my moulding techniques. Using a slighty "not as wet" mix with CRUSHED OYSTER SHELL really gives you porous rocks that you can put under slow running tap water and the water filters right throug the ropcks! They are not quite as strong this way, but you can learn to work with this with some practice. For the rocks with lots of holes ,tunnels and caves running through them, I do use the wetter silica fume mix quite often so as to strengthen them, but they end up very light and have a lot of surface area this way.
How does the porosity of cement rock compare with natural rock? Any measurements been made?

 

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Some of my oyster shell rock is more porous than most wild rock.
But, you can vary this as you like. The oyster shell is what makes it so easy to get the minor air pockets all over that allow tap water to run right through.
Any recomendations for beter colors besides the ugly grey of concrete?
Yeh, you can do two things, but they cost...
You can use white Riverside cment which is about $28 a bag rather than the grey Portland at $5 - $6 a bag.
But I find that white natural live rocdk undersides eventually turn about the same color as the Portland cment anyway.
Another trick is to use dyes.
Don't dye the whole cement right through or the color leaches forever...
A trick I learned at GARF last Oct at their confernece: You can mix up some thin runny slury of cment powedr and powdered aragonite dust and color it with red and blue RIT dye.
You can change the proportions to get the coralline colors you want and even do two or three colors splashed on one rock.
It can look quite natural sometimes. Let it dry and soak in vinegar to set the colors in better and then in fresh water to leach out a bit of the color that will leach.
I don't do this though, since I like real coraline better and I do not include coraline eating hermits in my tank to strip the coraline and keep it from growing.
I have two cment rocks in two tanks now. One is in a 100% tank raised tank - so now hermits - coralline eating one or not.
The cement rocks have been in their for about 2.5 months now and I just looked at them again this morning and the oner in the tank with no coralline eating hermits it way over half covered with nice coralline!
The rock in the other tank, a 75g with 10 or 12 C. digueti, is still almost comletely dull gray-green.
It does have a few coraline spots now, but even though this second rock is fancier with hole tunnelled through it, most people woyuld not buy it qat a shop because it looks dull.
What brand of sauce do you recommend to go with the pasta in the rocks, and would merlot or cabernet be better??
I like the white sauce, but not much on names. I think it's Alfredo sauce...???
lol ;-)
I also like fettachini better too (for taste anyway.
Has anyone considered the possible side effects from using RIT dye in their reef rock??? Do people even know what this might put in the water?
I do not know and have not checked since I don't plan to use it. One guy told me his tank water was purle until he took the rocks out a couple months later.
What are corraline eating hermits I have not heard of them?
I believe all hermits eat some coraline, but some really go to twon on it. They eat it like some folks eat hotcakes on the fourth of July!
C. Digueti
That is the most commonly available of the coralline eaters. It is often called names like "Mexican red legged hemit crab" or Red leg hermit or "Blue spot red leg hermit"...
From our discussion board:, My question to him would be if he has heard of using clay to create rocks and if it's safe. Because I'm wondering if there are any metal ions trapped in clay bodies, I think there is some aluminum in it.

 

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I don't know of anyone using clay and I guess it might depend on if the caly has arsenic, silicates or other things that could leach.
Cement is very high in many silicate compounds, but they bind and stop leaching to any noticeable degree after the cement cures enough.
When will Coraline algae start to grow on new liverocks? Also what does Coraline algae looks like (shape, size, color) when it first appear on the rock?
Coralline starts growing imediately if spores are flaoting around in your water.
You will see them after about 7 to 10 days of the new rock being in your tank if conditions are good - little pink, purple spots.
Do some polyps or corals attach faster to the rock?
It has worked well for me with any coral polyps I have tried with other rocks.
I have made small cookies or blobs in the sand molding bed and then I can use these to attach corals to.
Concrete has capillary porosity - which means it can take years to hundereds of years for water to travel through. Since only the outside of the rocks isn't covered in concrete, how can these rocks sustain comparable amounts of bacteria?
I suppose if you make your rocks too solid or with not enough water or pourous holes from using coyster shell ... thqat you could have less bacteria.
I have had good luck with tanks with some cment rock in them.
GARF has had good luck with one of their tanks with 90% cment rock, but hey do not have a 100% one yet, but I don't think that matters.
Jake Levi is the only person I know of with some tanks with 100% cment rock.
He says they do well. Others might have them too???
I plan on making a reef with the numbers molder from cmnet in the shapes of "1" through "9" so I can have a "reef by numbers" - serious-
I do want to set up a 100% cment rock reef too.
If you are adding cured rock do you discourage adding KW as a safety precaution?
Yes, I would discourage adding extra KW isnce you could get a minor leaching from the rock for a little while and if you only cure you cement in fresh water and no "saltwater followup" then you will get a KW spike when you change the cured cment rocks to saltwater.
Lately several people have noted that coral fragments, such as Acropora sp., will not spread on to the concrete rocks they are glued too. Have you come across this, any idea why?
I have not seen it or heard of it, but I have an idea...
I have seen it grow onto the cment rocks just fine so far.
If they did not cure the cment rocks or plugs fully, that might do it for a little while only.
I actually can grow coraline very quickly on cmnet cookies that I have put uncured ito reefs.
They actually grow coraline as they cure since the KW leaching is getting caried off by the circulating tank water. Maybe your friends have used a polymer based cmnet???
Polymer based cments IMO are not that great for reefs since they are waterproof and will not grow bacteria inside, but mostly because they do not grow coraline as quickly and you cannot glue stuff to them with super glue.
Do you get the same amount of corraline growth on the homemade rock compared to natural rock?
Yess, I do, if I don't include coralline eating hermits with them.
If your numbers of coraline eating hermits in your tank are low, then it just takes a lot longer for the coraline to get a foothold and grwo - probably the harder slow growing varieties that are not as tasty???
But if your numbers of these hermits are high, then you will really have a long wait to see much coraline - pictures of this on my web site but not with cmnet rocks, just aragonite rocks and wild live rocks that have been stripped.
Have you tried using a runny cement and sand mixture to coat wraps of fiberglass screen, to make lighter rocks with more surface area?

 

[inf]

I have not, but you ought to try it.
I make something almost similar but not as light by dribbling down a network of cement in the sand molding bed and then covering some parts iwth a thick laer of sand (or crushed oyster shell)...
And then I dribble down the next layer of cment over the sand layers I just put down and I keep puting down pockets of snad and then layers and streeks of cement to build a honeycombed rock with caves ande tunnels.
I got the dribbling techniques from a potter who makes cmnet rocks opf some different and somewhat similar shapes.
Her name is Karen Holt and you can also see some of her cmnet rock made with Riverside cement in that article on my web site.
ok, last Q for the night
My biggest question is, simply, why? Why? A reef is based on biodiversity. Solid concrete for biological, chemical, and mechanical reasons makes no sense to me. And, mixing up sand and concrete and forming things sounds like a nifty little craft project, but of what value is the time if the result does not produce the end result of biodiversity and function?
Two answers that should take care of that question - I hope.
First, you can gain nice porousity with cmnet using the technique listed here and in the article on my web site.
Next, YOu DO need to use live rock to provide seed material for these new "dead" rocks or they will remain that way! It is very easy to do this almost without trying.
Any life in the live rock that will no reproduce and spread to your new cmnet rock will eventually die and be gone anyway, so if this was really a problem then you would have to change wild live rock often.
OK folks, that wraps it up!

 

[squidd]

Old pic, but at least you can still see the rocks...
About 1/2 the rock structure in this tank is DIY Agrocrete...
You tell me which ones...

 

[nacl-man]

DIY rock is awesome if you have the facilities & abilities. I myself am not much of a DIY'er so I don't have any experience with it but man it would save a buncha money and allow you to really customize your tank.
The flip side is that lace rock or any other kind of base rock isn't that expensive, it still has to be cured to become 'live', and you don't have to mess w/ concrete.
It does work though I've seen many pictures when researching it myself and most you can not tell the difference.
Cheers!

 

[rustyj]

You can also go to GARF.ORG and they show you how to create agro crete which they turn into live rock by seeding it with their own GARF grunge. They have been a great resource for me and have been tank raising coral since the 1970's. They do alot of research on the sustainable propogation of corals and provide their research results for FREE. Check em out.