Fish Death continues.... Any solutions....

[moppy]

I've been in the salt water hobby for many years and continue to have the same problem:

Corals live and look great, fish die...

I can't figure it out as I've always been told that corals are way harder to keep than fish but I have no trouble with corals, just my fish...

It's 120 gallon tank with a 40 gallon sump.

FIsh list: Coral Beauty, Yellow Tang, Coris Wrasse, Leapard Wrasse, Bi-Colour and Scooter Blennies, Goby, Firefish and 2 clowns (I could list the other 7 that have died since the tank started 5 months ago but it' too depressing). None seem to be picking on the others.

Water quality is good, no nitrates, no phosphates, calcium and alkalinity are a bit low but not much... Salinity is fine as is temperature.

My copperband was the latest to go yesterday and he has been eating like a pig everyday, looked totally healthy and then dead. Looked at the tank last night and there were 2 large worms (looked like bristle) and about 5 nassiruis? snails eating him. When I put the rock into the tank I tried to do a thorough check to make sure there were not predators and I don't have any clicking to indicate a mantis (nor have I ever seen one).

Will these worms kill fish? The snails? I have no solutions????