From another thread, re.
algae control, I added nine Ottos to my 500l tank. They seemed to be doing well for awhile, then slowly but surely started to lose them and can now only count three. They have just disappeared. The rest of the community are doing well, but not these fellas. Not sure what to do about this problem.
I've read that they prefer a well established tank, which I think I have, and I can't seem to get my
nitrate level below 20. All other readings are normal. If the remaining three go, I don't think I will replace them!