reefrunner
Contributing Member
Someone told me excessive nitrAtes could stall a cycle. Has anyone heard of this? Agree, disagree?
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oneate7 said:I have heard of excessive nitrAtes stalling a cycle, but never at the ammonia level per se... always at the nitrIte level (i.e. nitrItes won't go down). The nitrItes then inhibit the ability of bacteria breaking down the ammonia, resulting in a stalled cycle. The fact that you're not seeing nitrItes makes me think that this isn't the case.
After doing some more research, the only thing that (sort of) makes sense is that additional, heterotrophic, bacteria are converting the excessive nitrAtes back into nitrItes and ultimately ammonia. Cyanobacteria is an example of heterotrophic bacteria that is capable of reversing the nitrification process in the aquarium (apparently... this is news to me. Google cyanobacteria nitrofixation). The only thing that I can think of is that ~.5ppm is the point at which the autotrophic bacteria (nitrosomona and nitrobacter) and the heterotorophic bacteria (cyanobacteria) reach an equilbrium in their ability to process ammonia and nitrAte respectively.
Even in that case, I would expect that you would see nitrItes on your test... so I still don't know that that explains it. I should mention that PH levels seem to effect the ability of the heterotrophic bacteria to do their thing as well with a low PH being beneficial to them.
In either case, a good way to test is to do a big water change to reduce the nitrAtes in the tank. Also check your PH... if it's low, dose some buffer or baking soda and see if that helps get things back into the right balance. If your ammonia drops after either of those... then I guess that was your problem! lol
Hope that helps... I should probably get back to work .
Edited to Add: Came across this little nugget as well. Also related to low PH -
The final form of inorganic nitrogen common in aquariums is the ammonium ion. Ammonium is formed when ammonia picks up an extra hydrogen molecule, converting the NH3 (ammonia) to NH4+ (ammonium ion). Ammonium is non-toxic and is more prevalent at a low pH (this will be discussed in more detail in the Nitrification and Water Chemistry section). Ammonium will often catch another molecule to form an ammonium salt. Many hobbyist grade ammonia test kits do not distinguish between ammonia and ammonium, and may give a false high reading for ammonia. This is why a tank that has been in service for a long period of time without a water change may show an ammonia reading, but the fish are still alive. The water has become acidic due to the lack of buffering capacity and the resulting ammonium is falsely reading as ammonia.
oneate7 said:Well, maybe what I posted earlier is accurate then? Who knows . Your PH is a little low, but not so low that it should cause issues. I stand by my latest advice... large water change, see what happens.
I have done 3 10 gallon water changes over the last three days (20 gallon tank). Ammonia is still at .5ppm, nitrite has gone down to .5 and nitrates are now about 180ppm which means after 3 50% water changes they started at 1440ppm. That's a lot of nitrate.
My plan is to continue the water changes daily (today I'm going to attempt to clean the sand bed in the hob refugium and remove the rocks and vacuum under and behind) until the nitrates are very low.
Any thoughts?
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