Recent deaths in my tank

[the Dude6971]

I have 30 gallon with a 10 gallon sump. I have a skunk cleaner shrimp, a yellowtail damsel a standard clown and a firefish goby. 2 mexican turbos and a nessarius(sp) snail. I did have a scooter blenny and an emerald crab that have both recently died off the blenny was in for about 3 months and the emerald about 4 months. the tank itself has been up and running about 5 months. everything else seems perfectly healthy no one is overly aggressive and I am at a loss as to what happened to these two guys. all of my parameters are good and i have recently water changed about 4 gallons of water after I found the blenny had died. I found him on Thursday, checked parameters all was well so i water changed friday night. He had no visible signs of sickness and seemed fine the day before. then saturday I found my little emerald crab had died as well.
Does anyone have any ideas what could be going on? I have recently been adding purple up to help with my corraline growth could that be it? My Dkh is at 12

 

[beth]

Can you go ahead and post up your water readings, including ammonia, nitrate, nitrite, ph, temps, salinity. Also, discontinue the purple additive. Are you using any other additives? What are you feeding your fish?

 

[the Dude6971]

after checking nitrates again tonight they were high. not sure if i missed it or what exactly happened. (even though I tested them before water change) water changed yesterday and today nitrates were really high. so maybe they were off the charts before and I somehow missed it. that being said ammonia is 0 nitrites were zero and i have not been monitoring PH. I was told as long as hardness stays above 8 PH isn't all that critical for FOWLR. I feed a good quality food pellet Low in phosphate and high in protein and salinity is 1.022
so I have water changed about 15% again tonight and nitrates are coming down but still not 0, so i will water change the same again tomorrow.

 

[pegasus]

Unless the scooter blenny was eating prepared foods, it most likely starved to death. Scooter blennies are not actually blennies... they're dragonets. Dragonet's natural diet consists of copepods and small amphipods. It takes a minimum of 6 months for a tank to mature enough to have a population large enough to sustain a single dragonet, and it normally takes a tank of 75 gallons or larger to accomplish this. Tank-bred and tank-raised scooters are usually eating processed foods when they are sold, but many (if not most) dragonets are wild-caught. Unless you know for certain that it will eat processed food(s), do not get another to put in your nano tank. Emerald crabs will scavenge for leftover food, but the bulk of their diet comes from algae that grows on the rocks. Without an adequate supply of this algae, they tend to have the same fate as dragonets... they starve to death. Naturally, the larger they are, the bigger the appetite. As far as I know, emeralds don't have a very long life span. I've raised them from 1/2" up to 2", which is adult size. None have ever lived over 1 1/2 years. If it was a large crab, it was probably old. Also, if your nitrate level was high, it could very well be the cause of it's death. Invertebrates cannot tolerate high levels of nitrate.

 

[pegasus]

after checking nitrates again tonight they were high. not sure if i missed it or what exactly happened. (even though I tested them before water change) water changed yesterday and today nitrates were really high. so maybe they were off the charts before and I somehow missed it. that being said ammonia is 0 nitrites were zero and i have not been monitoring PH. I was told as long as hardness stays above 8 PH isn't all that critical for FOWLR. I feed a good quality food pellet Low in phosphate and high in protein and salinity is 1.022
so I have water changed about 15% again tonight and nitrates are coming down but still not 0, so i will water change the same again tomorrow.

Unless you have corals, dKH isn't important. With a FOWLR system, you should focus on Nitrates... and stability. Stabile conditions are more important than specific numbers of an element. Even if you had a tank full of hard corals, 12 dKH is at the high end. As long as dKH is between 7-8, your pH should be fine. Wide fluctuations in pH are far worse than low levels. As far as nitrates go, striving for zero is a bit of a reach. FOWLR can tolerate elevated levels of NO3, so as long as you stay below 10ppm, you'll be okay. If you add corals later on, you'll want it below 5ppm... or less depending on the coral(s).

 

[the Dude6971]

I actually bought the blenny before ample research. A mistake I will not repeat. of course the girl at the fish store was not much help. he did however eat pellet food and mysis shrimp pretty well. as for nutritional content I do not know. It is Ocean nutrition formula one pellets, Small pellet size. I am unclear on if the nitrates were already high or got that way after the deaths of the blenny and crab. but it would explain the crabs death. my cleaner shrimp seems to be okay but i plan to water change about 4 gallons again today because nitrates are still higher than I would like. they regularly stay at 0.
Where do you recommend the salinity for FOWLR be kept? and do you think i should continue with the Purple Up?
Thanks for the help guys, any other advice you have is greatly appreciated.

 

[pegasus]

Dragonets eat constantly, and since their dietary needs are so different from other fish, a meal or two a day of pellets and mysis may not have met it's requirements. They require food that is very high in HUFA, and that often requires live food. Not saying that they can't be kept without live food, but it requires vigilant feeding of the proper blend of foods, and frequent feedings. Lesson learned...

Natural sea water is normally between 1.023-1.026 SG, depending on location. As with dKH, stabile salinity is more important than a specific number. As long as it's within acceptable range, you should try to keep it there. If it gets too high, you can reduce it fairly quickly by removing portions of tank water and adding fresh water. If it gets too low, you want to raise it slowly by using premixed saltwater to replace evaporated water (top off) since salt doesn't evaporate. Purple Up is a gimmick to get people to buy a product to do something that will naturally occur without it. Yes, it speeds up coralline algae growth on your rocks, but at the same time, it throws elements out of proportion. Purple Up is nothing more than calcium and iodine in a bottle. When you elevate calcium levels in your tank, your alkalinity levels drop. Without testing these elements to make sure they're in the correct ratios, you can actually do more harm than good. These important elements are in proper proportions in your saltwater mix, as long as it's a decent salt. As long as there are adequate levels of Calcium and Alkalinity in your tank water, and proper lighting, coralline algae will grow without using an additive like Purple Up. Short story long... no more Purple Up.

 

[the Dude6971]

Yes, I was very sad about the blenny. But like you said lesson learned.
thank you for all the help. I will water change again today and hopefully get these nitrates back under control. Up to this point i have water changed Biweekly and it has been super stable. Hopefully it will return to that point.
Do you have any recommendations for another crab going forward?

 

[pegasus]

I used to like crabs, but I've reached the point that I no longer care for them. My current emerald had gotten a bit aggressive towards some of the fish, so I had to move it from my large tank. I have lots of hermits, but I'm waiting for them to die so I can stock up on nassarius snails. They are bad about killing snails, and I used to think it was for their shells. Now I believe they do it because they love the taste of snails. I haven't added any hermits in over a year, and I believe they are multiplying. I have more now than ever. Arrow crabs tend to be aggressive, and will eat small fish and shrimp. If I were going to get a crab, I might go with a sally lightfoot... but I'm not going with any more crabs... lol!