One of my tanks (20g) which was originally set up six months ago as a quarantine tank (just couldn't leave it empty!) is giving me a headache! While it's small, I have a Magnum 350 canister on it (love canisters!) and up until this morning it had been a fantastic tank! It had two 1.5" frontosas until I added three 1.5" peach peacocks this past Saturday. Well, yesterday I did a water change (about 20%) and this morning the peacocks were all dead in the tank and the frons are just fine! Checking the water revealed the nitrates are very high, so I did another water change after removing the little peacock bodies. Well, nitrates are still high! What to do?? I did water changes on all of my tanks yesterday and all of the other tanks are fine. Any help would be great! Thank you!