I've had my angel for about 2 months, and he's been doing really great in my 28 gallon tank with 2 platies, otos, and a female betta. I noticed one of the platies picking on him last night, and when I went to check it out, I noticed that many of the scales on the right side of his body are suddenly missing. He seems very weak and inactive and doesn't come to the glass when I come near the tank like he always does. I've turned the filter off, becuase he is so weak that he got sucked up against the intake. His fins look awful, and he looks skinny, but refuses food. He's been eating fine until now. I removed the platies and female betta, so it's just him and the otos in the tank. I know the other fish were picking on him a bit, but I can't imagine that they started the problem. They've all been great together until now, and it doesn't seem like something they could have caused.
The water parameters are great, and I use a liquid test kit. No new changes in the tank, execpt a couple new plants that I had in another tank. I had done an 85% water change a couple days before. I usually do them every week, although it has been every 2 weeks lately. Temp is always @ 80*. The angel is young, only about quarter body size. I'm probably missing a couple things here, just let me know.