Help with small angels dying

[Jimmer107]

I bought four quarter size angels at walmart, and over the past day and a half two have died. They are feeding very well, look healthy, swim actively, but two have died. The dead ones show no signs of injury or disease, and looked normal up until they died. I have various tetras, cats including otos, and plants in a 250 l tank. Any ideas what may be going on? I don't know what my nitrate levels are, but everything else including the otos are doing fine.

[HOSStile]

How long has your tank been up and running? How long have you had the other fish in the tank? How long ago did you buy the angels? One comment, perform water changes and test your water. Please let us know so that we can help you better. Harold

[Jimmer107]

The tank has been in its present setup for about 3 months. Before that it was a cichlid tank for several years until I changed it over to a planted community tank. It had 18 assorted tetras and cats and on Friday I added 4 angels and 4 otos.

I have been changing one third of the water every week, and haven't had any problems up to now other than a small ick outbreak when I put the first fish in.

I don't have a test kit right now, so can't provide that info. I am using 2 AC 300's. The tank is about 60 imperial gallons.

The angels had come in to walmart the day before I bought them, but looked fine in the store.

[Jimmer107]

I've noticed some of my otos have red gills. After checking this out on the net, I believe the problem is ammonia poisoning - too many fish added too quickly. Hopefully some large water changes will help.