Fish problems with my Shark

[nmoran]

I've got a banded cat shark whos about 16 in. He's in a 210 gallon tank. My problem is every time I introduce a new fish they get sick with in a week. The only two fish in there are the shark and a clown fish. The shark is very mild and doesn't ever disturb the clown. I was told by in a fish shop that the fish are dying because they are affraid of the shark. The fish have been a regal tang, a powder blue tang, another clown, anemone, and a damsel. The clown and the shark have never gotten sick from the fish getting sick. The water quality is very good. So what's my problem?

 

[risc]

Generally speaking a shark is hardly ever going to get sick from diseases that other fish contract due to their high levels of immunities to toxins and bacteria. Chances are your tangs got sick from spikes in the water caused by the sharks feeding. Your tang could have easily infected the clown and the damsel. Damsels get along wonderfully with my bamboo sharks. They don't bother them at all. I did at one time have a few blue devil damsels that picked on some baby bamboos I had. But a larger bamboo ate those damsels and they learned from their experience to not mess with the sharks.
It is also possible the clown and tangs could have died from stress related to such a large fish in the tank with them. But it is highly unlikely that is the case for the damsel.
Jim