ammonia spike

It seems that the last time I went about uprooting all the gravel in the tank I may have upset the aquarium's nitrogen cycle.

Because we've got an ammonium spike starting quite out of the blue. I'd simultaneously given the gravel a good cleaning and wrung out the filter in the pail of water I'd just siphoned out. But even washing the filter (and boy did it need it) in "good" (un-chlorinated) water didn't seem to be enough. I have a second filter in the tank, a sponge filter than burbles away in the corner; usually I rely on those to provide biologic filtration. But having started a second aquarium recently, I'd moved the older, established filter to that tank and installed a new sponge filter in the main.

Too much at one time!

Now I'm changing 25% of the water every day and mowing through water conditioner like it was going out of style.