Oi!
Well this IS an interesting conundrum. Chromis you can't keep? It's like saying you can't keep 'WEEDS'.
The acclamation question would have came up with your invertebrates since they handle 'change' worst than fish. If your shrimp and grabs are OK that 'shouldn't' be the problem.
You would think that if the corals are in bad shape, the fish would go 'next' but if your corals are OK........
If another person or persons don't have problems with the fish from the same store, than I would guess it's probably not the fish or the way they were caught.
A UV filter would take care of the 'buggies', but if the fish are showing no signs of disease before they die, then that might be overkill, but I feel that a UV filter kills more bad than good [i.e. coraline algae does NOT die if you put one in a reef tank!]
Are you sure you don't have a 'nasty crab?' or something like that?
Your prams are better than mine, I'm assuming that the 'water' is OK since your corals are doing OK..
You are feeding the fish right [sorry I'm running out of ideas here]
What are you feeding? I'm assuming again that it's a varied diet? I would not feed a hand made 'mush'. There is too much 'gunk' on store bought food that WE eat that can if not 'cooked' or prepared by 'fish food manufacturers' get into the tank and kill the fish.
How is the temperature? Is it fairly constant? That should also effect the corals too but the fish [well mine anyway] should take a temp swing.
You mentioned the mulitmeter, there will probably be 'some' charge in the tank, if not from the equipment, then at least from the meter 'reading' the charge.
Darn, I can't think of anything else, except a 'bad crab' but that 'should' have taken out the lawnmorer too.
I'll keep thinking.
Cheers!
nigle
!~!