wasting disease?

[Jessi84]

Situation: Bought 7 chromis/damsels (look like Acanthochromis indicus after some research) about a week ago or so. I have been slowly loosing them to an unknown cause (possible parasite or disease-not sure) they are eating well and no other animals seem in distress. I am now down to 4 and only one is showing signs of distress by isolating itself from the others. I've only found one dead (of the 3 that are missing) and it did have an open wound on it's side (I do have many crustaceans and ALOT of rock -leaving numerous possibilities).
Symptoms: not gaining weight
No known predators in the tank and as far as I know, these are schooling fish, so I'm not sure if they are isolating each other one-by-one or what is going on. They appear to be non-aggressive toward other species as far as I've seen and occasionally chase each other and reunite to school.
I would like to keep what I have left since they arrived in the store as "chromis" and am not sure if I can replace them.
Any suggestions would be appreciated to aid in researching the root cause.
Thanks, Jessi

[Gerwin]

watch. isolate. investigate.
Its to hard to answer this type of question well over a forum, its all just guessing when you are not seeing it hands on.
But by the facts given if they are MIA, then predation is possible, infection or wound on the mark but you make educated guesses by the surrounding facts.
These are things best helped in person at the shop, I honestly rarely type over a paragraph unless of course I am on a rant and its early and I have a pot of coffee in me...

[Jessi84]

LOL...thanks...#4 is MIA too now. Only symptom with the other 3 so far seems to be lack of weight gain...eating well though. Can't really isolate...too much rock to catch them.

[Lancelot22]

Wondering if anyone has heard of an aquarium fish disease that would be attributed to the wasting appearance of my rainbow fish? My second batch of rainbows that I bought a few weeks ago are not looking very well. My first batch of rainbows are fat and happy, but there are four of the new batch that has slowly become so skinny. And not just skinny but even under the lower jaw were the gills are are even indented from the lack of fat. they are like pencil thin with no shape at all. they hang around one corner at the top of the tank and do not seem to eat at all. At first I was wondering if the healthy bigger rainbows are getting all the food first, but I have put food above them but they do not seem to have any interest. I found one of the thin ones dead this am, among the frill plant. I am sure that another, a very large and long male will not make it through the night.
Is there a disease that has a name for this wasting away appearance? And is there anything I can do? Im hoping that what ever is wrong with them will not infect the healthy rainbows or the Discus or any of my other fish in the 55g tank.
Any suggestions on what can be going on? And what can I do about it?

Thanks so much...for any help at all.

[Gerwin]

internal parasites can cause this, and metronidazole can help, I have it in stock.