denitrification and dissimilation

[Guest]

ive noticed since i raised the temps in my tank to battle ich that my nitrite levels have gone up to a steady .25, even soon after a pwc. after looking into the matter i found some info on denitrification and dissimilation. this is a natural process which occurs when o2 levels drop and nitrates are converted back into nitrites.

could this be happening in my tank? or am off base here.

 

[jcarlilesiu]

I have never heard of this natural process, however if you have raised your temps then yes it is completely plausible. Increasing tank temps lower the level of saturation of O2 in the water. Many times when battling ich, its suggested to lower the tank water so that filter return water causes a splash on re-entry to the tank. This helps keep O2 levels up, and in return would prevent the situation you are speaking of.

based on this theory, I would bet that nitrates arn't actually converted back to nitrites but rather die due to suffocation which then contributes back to the whole "cycle" process. Either way, I would add an air stone, or cause some surface aggitation to assist in keep O2 in the water while you treat for Ich. HTH

 

[Mosaic]

The Ecology of the Planted Tank by Walstad mentions the denitrification process. It does happen. I don't understand how, but it's possible.

Along with what's already been suggested, I'd recommend getting some fast growing plants in there (hornwort, water sprite, etc). They take up a lot of nitrites and they'll put some O2 back in your tank. Just scoop them out into a bucket or something at night so they won't use up the fish's oxygen when they're not photosynthesizing.

 

[Guest]

there is agitation @ the surface along with an airstone providing a powerful fine mist of air. my concern right now is the nitrite level and why it is there. at night there would be plants, fish, beneficial bacteria, and even algae competeing for o2 in the tank. since high temps reduce the level of o2 held in the water, it could be plauable that denitrification is converting nitrates back into nitrites and due to the fact that test results are showing nitrite levels @ .25 and nitrate levels @ near 0. i cannot figure out any other reason why nitrite levels would be there or why the bio filter would not be converting this to nitrate.

 

[rkilling1]

i would test for NO2 and NO3 just before lights out and then retest in the morning prior to turing the lights on. the data should show weather the biofilter is unable to convert the NO2 to NO3 or that denitrification is really occuring.

 

[newfound77951]

Denitrification can and does occur all the time in natural systems. It requires the absence of O2, and is likely occurring in your substrate. It probably goes on in isolated patches all the time, but with the temp increase, the extent of anoxic patches in the substrate will increase due to the decreased saturation of O2 at higher temps and also due to the faster rate of organic matter breakdown at higher temps.

This is not isolated to your tank; everyone probably has hypoxic or anoxic patches in their substrate to some degree. Gravel vacs will help. Also note that the final product of denitrification is the removal of nitrogen as N2 gas! I believe there are some schools of thought in SW tanks for keeping the substrate anoxic for this purpose - to remove nitrogen from the system.

 

[Guest]

exactly, nitrogen escaping into the atmosphere is the final phase of denitrification and i have been doing thorough vac's, more for ich purposes than anything. however, before the final phase of denitrification the fact remains that nitrites remain where they are at. with the increased vac's, the organic waste in the substrate is kept to a minimum, it should help things a little. now the question is the nitrite level @ .25. how dangerous is this to the fish?

 

[src]

Remember, the difference between Nitrite (NO2) and Nitrate (NO3) is an oxygen atom. First, that means that a lack of oxygen will either inhibit or prohibit the conversion of NO2 into NO3, depending on how bad the oxygen deficiency is.

Second, NO3 is not as stable a molecule as NO2 (according to some information I have found), which means that in a low oxygen environment other molecules (especially nitric oxide, NO) are likely to strip that third oxygen atom from the NO3. Add an oxygen to NO, and you are back to NO2.

 

[newfound77951]

I'd keep up with the PWCs, but unless it goes higher or you have super-sensitive fish, it'll probably be OK. Honestly with the accuracy of the test kits used for aquarium purposes there is a huge +/- on all tests anyway, and it could really be very close to 0 (or higher than 0.25 but let's be optimistic!)

 

[Guest]

ok, cool. im doing pwc's daily. ty.