Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
If you are doing that little dose of ammonia and the nitrites are still spiking then there might be 2 things going on.
Something in the tank is slowing the growth of the second population of bacteria. (This group is already slow, even with everything in their favor)
Yes, I would do the massive water change you are thinking of. Really get in there and vacuum the substrate. Perhaps refill (don't forget dechlor) and vacuum it all out again. That would be 2 water changes of 100%.
Set the parameters in the water to suit the bacteria:
GH and KH ought to be higher than 3 German degrees of hardness, and much higher is not a problem. Lower is a problem. These bacteria need a few minerals, and use the carbonates as a source of carbon.
pH on the alkaline side of neutral. Anywhere in the 7s.
Temperature in the mid 70sF is just fine, warmer is not a problem as long as the water is high in oxygen. Warmer water holds less oxygen.
Good water movement in the tank to encourage high oxygen levels.
Then redose the ammonia to just 1 ppm and see what happens.
How fast does the ammonia get removed? What does the nitrite do? Try dosing to 2 ppm. ammonia.
If that does not get the cycle going, then go buy some of the right bacteria. Look for Nitrospiros. These are the actual bacteria you are trying to grow in the tank. Do not waste your money on anything else. If you go buy this, do another 100% water change to drop the levels of ammonia and nitrite pretty close to 0 ppm. After the Nitrospiros is well circulated add ammonia to 3 ppm.
Ammonia is toxic to most fish at lower levels than nitrite. Ammonia burns the gills and the soft tissues. It is toxic to fish at levels as low as .008 mg/l for as short an exposure as 24 hours (Rainbow Trout).
Nitrite crosses the gills and enters the blood, causing brown blood disease. If there is any chloride in the water nitrite is less toxic. Levels as low as 1 mg/l can be toxic if there is little or no chloride in the water.
Sensitivity levels vary among fish species, and stages of life. Fry are more sensitive than adults, for example to ammonia, but larger fish are more sensitive to nitrite.
There are so many variables that it is difficult to say if one is more toxic than the other. I think I would rather see nitrite in the water than ammonia. Fish can reverse the short term damage from nitrite, and can be protected by adding salt.
As a general guide if there are toxins in the tank with fish the ammonia should be kept under .25 ppm and the nitrite under 1 ppm. Better to avoid the problem.