ARRRRRRGH! Nitrate!

[samfishes]

ok, so my nitrate problem isn't fixed. Here's the details:
I have a 350L (~93 gallons). We have a fluval 305 running on it which is well established, and also a fluval 405 which has been going for a week and a bit. We also have a V2 800 skimmer and a pump to circulate the water on top.
Livestock: 5 x blue green chromis, 2 x yellow tails damsels, 1 x clown, 1 x yellow tang, 1 x naso tang, 1 x unidentified (!), 1 x jewel puffer, 1 x teeny cleaner fish (who hitchhiked with the puffer), 1 x pink lobster
Ammonia and nitrite are as close to zero as were gonna get - basically there's none in there. We bought this tank as an established system but we later had to add the fluval 405 and skimmer as the guy didn't sell it with enough filtration and there was no skimmer. We did a 30% water change last Wed which brought the nitrate down from ~ 110ppm to 20ppm but this shot back up over night. We thought this was because the new kit wasn't working and sure enough after another couple of days the new filter & skimmer had brought it down to 50ppm (we think - the tests are a bit frigging hard to read!!) and a further water change of 10% got it down to a nice healthy 10-20ppm Wh added the puffer ansd naso on sat which our shop said was fine to do and i tested it last night and it;s back up high again!!! HHave a few little corals which seem happy enough and the fish seem ok. Feeding twice a day and all is eaten. No deaths, so no decaying fish in the water. PH also looks a bit high (i'd say about 8.3 - 8.4 but again, the test is open to interpretation!!!) Please help, advice gladly taken!!!

 

[xcali1985]

I see that you have posted a few threads on this topic. I haven't read over them so ill ask a few questions about your system.
1. You mention that you bought this system "established", how long was it established?
- Tanks over time develop nitrates in the sand beds of the tanks and organic matter breaking down within the rocks. Moving a tank can stir up lots of this bacteria. Over time alot of tanks (especially with novice maintenance) develop old tank syndrome.
2. Does it have a Deep Sand Bed (~3+ inchs)?
- DSB pocket nitrates, if you have something in your tank that is stirring it all up for the first time, this may be the cause?
Ill list a few reasons possible for your nitrates, but don't limit your investigation of your problem based on my theories. I read that you listed what 14 inhabitants, in a 90 gallon. That is probably overstocked. I have been told that each setup is different and no one systems are the same. However, you know when you have maxed out when nitrates become a problem. Basically you are producing nitrates faster than the tank can remove them, be it algae, or nitrogen.
Another reason may be simply feeding, although you say they eat all the food fish are often competition eaters and will eat until its gone most times, in the wild most fish eat constantly, be it mircofauna or whatever. Cutting back your food may help reduce fish waste and reduce nitrates.
Now ill list some solutions that you can take to remove nitrates. There are denitrates its a separate unit that you will need to purchase and it aids in the removal of nitrates most people don't go this route. Some increase water change frequency, to every week to keep up with the bioload. Me personally I change 10 gallons every 2 weeks on my 80 gallon. A total of 25% a month. That changes if I am having problems, Ill change 5-10 weekly to control algae outbreaks or such.
The best way that we know how to remove nitrates from the water is through natural processes, ie. photosynthesis. In order to do that you need to run a refugium, be it undertank, intank, or hang on the back. Placing macroalgae in it with a light, it uses the nitrates and phosphates to remove them from the water and you simply trim it.
There are several corals that also remove nitrates abeit very little, but an example is xenia. I have even seen them die in tanks that were too clean meaning 0 nitrates. Clams are noted as removing nitrates also, although they are expensive and the impact is probably no more effective than the xenia i mentioned.
So there you have it, some questions, reasons, and solutions. If I were you I would start by selling or trading both tangs and the puffer for smaller fish(maybe a wrasse and/or some gobies) they release a lot of waste because of their feeding habits and will probably out grow your tank eventually. Tangs eat vegetable matter(algae) and their waste breaks down to to its components, which as I stated before is nitrates and phosphates so that is what releases back into the water.
I know this is lengthy, but I want to help you solve your problem. Try cutting back feeding first, look into HOB and In-Tank Refugiums if that dosen't help. If possible add more live rock, and look into lowering the community count in your tank.
Also don't expect instant results. Every now and again I will add to much microplankton to my tank and will develop a brownish layer on my sand. Usually takes a week or so to clear up. Nitrates will slowly lower with proper care and maintenance.

 

[samfishes]

Thanks very much, that is really helpful

I will probably take some fishies back to our store this weekend when we pick up water as when we bought the tank it already had 10 inhabitants.
I think it had been going a while - more than a year and everything got very stirred up during the move so i guess this would release alot of nitrate if there was any in the sand. it doesn't have a particularly deep sand bed - mas an inch and a half.
I will definately look into the micro algea. I adore my tangs and puffer

so i'd love to keep them if we can - they are the only ones we've added ourselves! but i do agree we are probably overstocked - that was the problem with getting the tank already filled - alot of the fish we wouldn't have chosen ourselves, but i don't want to keep uprooting them as i think it's cruel (still, not as cruel as poisening them with nitrate i suppose!)
I will keep you posted - we are still very new at this hobby so i am hoping with help like yours we can get them tank as nice as possible for our inhabitants - all i want is nice happy healthy fish!!!!

 

[srfisher17]

If nitrate goes from 20 ppm to <100ppm overnight; I'd suspect a faulty test kit. Also, a 10% water change would not reduce nitrate from 50ppm to 20 ppm . A 10% water change should reduce nitrate by 10%. Either your test kit (how old is it?) or your testing methods are faulty;IMO.

 

[flower]

Aside from the lobster, nitrate won't bother the fish a all. They can stand it very high with no ill effects whatsoever.
I personally doubt your nitrates were 110 because your lobster is still around. Nitrates are dangerous for corals and inverts over 40..Like I said, fish don't care.

 

[beaslbob]

Could be everything is fine.
It is a newly moved but previous setup tank. It is normal for planted tanks to have high nitrates but no ammonia nor nitrites for a few weeks until the aerobic bacteria get reestablished. then finally nitrates drop.
the reason is the plant life (corraline or macro algaes) actually prefer to consume ammonia and is ammonia spikes they will consume that over nitrates. So zero ammonia but lotsa nitrates. Then as the bacteria expand and consume the ammonia, the nitrates finally drop down.
You might try some macro algae just to be sure.
my .02