Diego

Incomplete nitrification makes sense only if you think there is already an imbalance between the AOB and NOB bacterias before overfeeding. Lets say if normally a system can cope with a level x of ammonia as it has enough bacterias (AOB+NOB) to convert it to nitrates, if you increase the level of ammonia to 2x, then you'll will experience a mini cycle: a spike of ammonia followed by a spike of nitrites. So why do I see the spike of nitrites but not the one of ammonia? I think because the plants are taking in part of the extra ammonia while the AOB population grows, avoiding the ammonia spike. So now a larger population of AOB is producing more nitrites but the NOB population has not caught up yet and plants are not helping there. I register the only spike of nitrites. Assuming I have enough fast growing plants which could cope with the extra ammonia from the overfeeding, I should not encourage the nitrification via biological filtering which only increases nitrites and nitrates. I think this is the idea behind chapter 7 and the Q&A on page 111 of Diana's book. Thanks Shadow_Arbor, for the inspiring conversation. I have an experiment to run now. I have already gone through the water changes and yes of course it does work. I'll try something else now: removing a sponge filter.

Just to make clear, dewormers are very hard on your aquarium. They will kill hydra, planaria and any other worms (good ones too) and snails. I will use them only as last resort. Dewormers will not kill leeches ... just in case you were asking that 🙂

Good ideas Shadow_Arbor. I re-read chapter 4 (nitrite accumulation) but I am not convinced. Incomplete nitrification does not make sense. The tank has been established for quite some time and this unbalance is only caused by me adding extra food. Normally there is no accumulation of nitrites, the temperature is fairly constant as the tank sits in my living rom and the ph is high (7.8). Nitrate respiration could be a thing as the levels of nitrates peaked at 30ppm during the nitirite accumulation event. I have a substrate that would invite anaerobic bacteria but it should effect the tank also when not overfeeding. The other option is that unlike nitirites which are consumed only via nitrification, ammonia is removed by two processes: nitrification and plants. And plants prefer ammonia/um so they compete against the AOC. If this is true, I should get rid of some biological filtering (sponge filters) and let the plant to take the ammonia instead. Am I over filtering?

The bad side of fenbendazole is that your tank will be inhospitable to snails for several months no matter how much active carbon you use. The canine version is also poorly soluble so it stays in the substrate for long (slow release). If you can change the substrate it would help. There is a goat dewormer which is liquid and works better than the dog one. I used planaria zero and it worked against hydra too but has the same effect on snails.

Of course the other thing I did not consider is fishfood releasing nitrites directly rather than being broken down to ammonia first. Is that even possible?

Recently I noticed a noticeable level of nitrites (0.25 ppm) lingering in the tank after few days of overfeeding. I have been testing the water daily with the API test kit and never observed any level of ammonia >0. So my theory is that ammonia oxidizing bacteria (AOB) act faster than their relatives nitrite oxidizing bacteria (NOB) so that there will be always an accumulation of nitrite while the excess ammonia is converted to nitrates. Also AOB seems to be generated faster or live longer than NOB. Is this plausible? Has anyone experience a similar issue? Anyone know how to boost NOB? The tank is a well established 20 long very heavily planted with gravel-capped dirt substrate. There are 6 white clouds plus lots of cherry shrimps. The excess ammonia is caused by overfeeding. Temperature is around 73F. Two small sponge filters on each side of the tank.