Why is my nitrate so high?

[Blue Tang]

Hello all again, I seem to be having trouble with my nitrate levels? I only feed my fish every two to three days and only then give them very little as i know to much can up the nitrate levels.As far as I know I have heaps of coral bio filter to break waste and i have done two water changes in the last three weeks, there seems to be some kind of growth on one of the rocks, it has bubbles coming out of it ? ive put a pic of it up as well as my skimmer , sump etc , any advice will greatfully taken on board , Thanks , i am also using Phosguard in the sump.and used a bottle of cycle to build up the bacteria.
Blue Tang :? :mrgreen:

 

[ChrisRD]

How high is your nitrate level? Low levels are not really cause for alarm IMO.

With the amount of live rock/sand you have in the display you shouldn't need any artificial biomedia in the sump. The way you've got things setup (basically like a wet/dry) it's doing lots of nitrification but probably little denitrification - thus the excess nitrates. Do a search here for "bioballs" and you'll find a lot of relevant discussion.

Also, it's a bit tough to tell in the pics, but it looks like you may have some detritus build-up on the substrate in the display tank. IME making an effort to get detritus out of the system (syphoning, frequently changed micron socks, blowing off rock/sand with powerheads, etc.) makes a big difference in water quality.

HTH

 

[Len]

Your other pics got posted here: http://reefs.org/phpBB2/viewtopic.php?t=111842

 

[IslandCrow]

I'm having a hard time telling from the picture, but based on your description, the buildup on your rocks could be cyanobacteria (a.k.a. red slime "algae"). Is it dark red in color, and does it come up easily if you aim a stream of water at it (like with a powerhead or turkey baster)? If that sounds like the same stuff you have, your high nitrates are probably a large contributor, so once you get those down, it will probably eventually go away on its own. It also tends to pop up in low flow areas.

I second ChrisRD on the artificial media. It does a great job with ammonia, but generally leaves the nitrates.

 

[Blue Tang]

So if i remove the substrate from the sump what will i need to do to get rid of the nitrate? I just always thought that nitrate was the last link in the chain of the bio system? is there another process that i can use to breakdown the nitrate even further? many thanks for all of your replies its great to know that there is somebody there to help if called on!!!thanks again!
Blue tang :?

 

[IslandCrow]

You're absolutely correct in that nitrate is the last link in the nitrogen cycle before nitrogen gas. The problem with the bio media you have in the sump is that because of its size and porosity, although it has a nice oxygen rich surface where nitrifying bacteria (bacteria that turn ammonia into nitrite and nitrate) can thrive, it doesn't have an anoxic layer where denitrifying bacteria (bacteria that turn nitrate into nitrogen gas) can live. That happens two places in a typical marine tank. First, it happens deep inside your live rock, so make sure you have plenty of that (1-2 lbs per gallon is a pretty good rule of thumb). Second, it can occur in a deep sand bed, which is usually about 4-5 inches of fine sand. Then, there are plenums and denitrifying corals, but I can't speak intelligently about those.

What you have there wouldn't be bad if you cleaned it very regularly. The way I understand it, it's not so much the bio-media itself that contributes to high nitrates, but the fact that food and detritus gets trapped in that layer and decomposes into ammonia, which is quickly converted to nitrate and leads to your problem.

That's a good skimmer by the way. I'm very happy with mine, especially for the price.

 

[Blue Tang]

Thanks very much for your advice mate , As you can see i have two sections of coral rubble in the sump and on the bottom is a section of calcium carbonate, so im thinking what i might do is to remove the carbonate and replace it with some very fine sand, does this sand need to have bacteria already in it? if so i can get it from the beach front where i live ,or is any fine sand ok? what are your thoughts on this idea please?

Thanks , Blue tang. :?

 

[IslandCrow]

Dry sand should work just fine. Just take a cupful of sand from your main tank and add it to the new sand, and it will colonize it with bacteria. If you have a bare bottom tank, use a rock from the main tank instead.

I wouldn't use beach sand, however. I can't give you any specifics as to why, and it may just be one of those urban legends running around, but it seems to be unanimous that beach sand is bad. You could probably collect it from the ocean bottom, but I have no idea how far out you'd have to go.

I'd suggest either buying dry sand specifically for aquariums, or getting sand for playgrounds/sand boxes from your local hardware store. The latter will be silicate based, but this really shouldn't be a problem. In your case, for such a small amount, I'd play it safe and get aragonite/oolitic aquarium sand (I've used both), but either should be fine.