Removed all Nitrate. Controled by O2.

[litebrite]

I found this by luck. I had a tank with Nitrates (FOWLR). I have hungry fish. And of course I had nitrates as a result.

I have few fish but I learned that when my water level is high there is little room for air at the top between the glass and water line reducing the O2 (oxygen) in the water (was my guess). Now this can't be good but the fish don't seem to mind. I keep the light on for 12 hours a day and algae grows so that might be making O2. The tank is almost completely sealed with the exception that the filters hang off the back and are exposed to some air. No bubblers, no protien skimmer. I have gone almost 2 years now with no NO3 (nitrate) unless my water level drops and I get lots of splashing water and fresh air at the top which them my nitrates start showing up. Then I fill it back up to the rim and seal it off and NO3 drops to 0 again.

At least 25% of the tank is all Tuffa rock.

I read how bacteria deep in side if live rock starves for O2 and when no oxygen is available it will take the O2 (oxygen) from NO3 (nitrate) turning it to NO (nitrogen).

My other guess is that low O2 might be stoping the breakdown of waste in to ammonia and it might not have anything to do with NO3 reduction. Live rock reduces a small amount of NO3 normally. Maybe I am slowing down the Ammonia build up or both. The crabs eat the algae so that gets recycled back in to the water as fish/crab waste.

I don't claim to be an aquarium expert at all, just sharing what I think is happening. Please comment your thoughts. Thank you.

 

[cmor1701d]

And your pH is reading....?

 

[litebrite]

PH is 8.3. Hardness is about 220 a bit high (guessing from the Tuffa rock).

 

[Kurt_Nelson]

I have few fish but I learned that when my water level is high there is little room for air at the top between the glass and water line reducing the O2 (oxygen) in the water (was my guess). Now this can't be good but the fish don't seem to mind. I keep the light on for 12 hours a day and algae grows so that might be making O2. The tank is almost completely sealed with the exception that the filters hang off the back and are exposed to some air. ...

Maybe I'm missing something, but I don't really think where your waterline is really matters. You say there's "less room" for air, but there's still the same surface area of water exposed to air... whether the tank is at the rim, or it's half full. "Almost completely sealed" means not sealed. It either is or isn't. If air can get in around your HOB equipment, then it's there - regardless of your water level. If your pH level is at 8.3, then you don't have an issue with lack of oxygen.

Not sure how big of a tank you're talking about here, and not sure how much water your letting evaporate before you top it back off again - but just plain dilution might explain what you're seeing. If you're not talking about a lot of nitrates to start with, and you're replacing a LOT of water, then you might just be dropping the nitrate level below the detectable level of your test kit.

 

[melosu58]

Maybe I'm missing something, but I don't really think where your waterline is really matters.

Kurt is correct. It makes no difference where your water line. Aeration is obtained by surface aggitation. Hopefully you dont have glass hoods on top. I see where you said it is sealed. Have a PH pointed to the top and create a good surface aggitation as this will put the needed oxygen in the tank. Any glass tops will hinder the process.