Over the past couple of months I've had lots of problems with my cherry barbs. I had 6 cherry barbs and 6 red eye tetras. Over a couple of weeks two barbs died. I then watched as our third last barb died. It just seemed stressed and didn't eat. It wasn't swimming weird and the body and scales looked normal. So we went out and bought 6 new cherry barbs, bringing the number up to 8. That was 2 weeks ago, and two have died since. I'm pretty sure another one is going to die. It's swimming in an upper corner of the tank, sticking its nose into the corner. I'm no genius, but I'm pretty sure I know how that's going to end.
My water is:
Water changes are every week or two, replacing 20L of the 75L tank, along with gravel vacuuming. Food is usually flake, with bloodworms once per week. I also have tons of MTS. Maybe I'm overfeeding the tank, but I only put one pinch in a day. So maybe I'm actually underfeeding. Why can't fish speak English and just tell me what is wrong?
I've been turning off the aquarium light bulb to keep the hours of light down to keep algae away. The light turns on around 9:30am, turns off between 1 and 2:30, and turns of for the night at 8pm. Maybe the lights stress the fish, I don't know.
The tetras seem to be doing fine. I lost one early in the summer to dropsy but other than that they've been fine.