Hello, last week my big L. pictus catfish died when it appeared healthy. It is in with dats, hoplo cats, cory cats, G. eques cat, peacock eels, motoros and a crenicichla. I was puzzled because it showed amazing growth and the last addition to the tank was probably 3 months ago with the cories, so I figured they were healthy. My cat randomly stopped eating and died in one day, though his appetite wasnt what it should have been starting 3 weeks before he died. Dont get me wrong, he still ate alot of food, but no where near the amount he ate before. I figured it was because he hit the 20" mark and was starting to slow down. Anyway, he died and all the other fish are eating and active. However, yesterday after I fed bloodworms to the rays (they eat massivore, cichlid gold, shrimp and blood worms, however one is only tasting the pellets it seems and spitting them out its gills, but eating bloodworms well), anyway, after feeding BW yesterday, I noticed that one stingray had stringy stool that was about the same color of the blood worms. However, I noticed a white string floating around, didnt look like a worm but you never know. Anyway, I hate medicating and havent lost a fish in a long time until the L. pictus. So should I medicate for internal worms and is there any medication that will not kill my benificial bacteria off? Thanks!