I had 3 tsn cats for a few months now. They are about 8 inches long. Tank is a 180 gallon with 0 ammonia. Ph is about 7.2. Nitrates around 10. All 3 of these fish were eating tilapia until recently. I have one that started eating the massivore pellets that my peacock bass passed on. The other 2 stopped eating since the biggest one started taking the pellets. Now one has died and I'm not sure why. It looks healthy except for the fact that it's dead, if that makes sense. Any ideas. Don't want the other one that's not eating to die.