I have found with other fish that if a fish is kept in poor water it seems to cause damage to organs and will eventually kill the animal. This may seem sudden and for no reason as the fish seemed healthy and can be months after the fish is kept in good conditions. This is why I think so many rays die suddenly for no apparent reason.
One experience in particular that sticks in my mind. I got some fish form a guy that had a grossly overstocked tank. The water quality was very poor yet the fish seemed OK at the time. He was going to get rid of all the fish and turn it into a SW tank. So I was able to take what I wanted for free. I took 5 fish. They went in two different tanks at my house with some other fish. All the fish were in great water and doing very well. Then several months after I took the fish, they started dying one after another. 4 of the 5 fish I got died all within days of each other. No other fish died except the ones I got from this guy and they died all of a sudden. Eating and seemingly health one day and dead the next. My only explanation is the poor water quality they were in had done damage to organs and eventually killed the fish.
The only fish I have left from that guys tanks is a silver "shark" catfish that is about a foot long now and is actually doing really good. It seams this cat fish species is tough.
The fish that died were 1 normal pleco, 1 "chocolate" pleco and 2 angle fish. All would have been basically considered adult size when I got them. I had all these fish for about 4-5 months and then they all died within a months time. I had them in good water in 2 different tanks with several other fish and they were the only fish that died. All the other fish that I had with them, I still have today and are doing good.
. He was a male motoro, his disk was around 12 inches. He was a great ray, very active and social. He was with us for 2.5 years. I really don't know what happened . he was fine yesterday, my other 2 rays are fine. he had no wounds or damage. The water parameters are spot on. I'll post some pics later. I'm just to bummed now.
