something is wrong with my green chromis

[lindy]

I have been ever so slowly setting up a sw tank, the tank has been set up for about 3 months with LR in it. Well I put 7 green chromis into my 120g on sunday, they are the only fish in there right now. I got my water tested by the lfs before I got these fish. (I was paranoid and wanted to make sure all was ok!)
Anyway tonight when I got home to feed and check up on my new additions I noticed that one of them has a problem. The tail fin is gone! And the base of it is now has no pigment. It really looks like its down to raw flesh.
One of the others is hiding aswell but does not seem to be suffering the same thing, and does not appear to physically have anything wrong, but I am still a bit worried. The other 5 are fine, they ate their food tonight and are as active as when I got them.
Water Params:
Ammonia 0
Nitrite 0
Nitrate I dont actually have the tester for as the shop did not have one for me to buy, lfs guy did check it though and said it wasnt measurable on his test
Temp 27c
Salinity 1.024
I cant post my pH because I cant find my test kit to be able to tell you
Any ideas? What should I do for my lil fish? Have I done something wrong? This is all new to me so I am not really sure..
Thanks for the help.
Lindy

 

[lindy]

Thank you for the quick response. I havent noticed any aggression in the tank but i guess that doesnt mean there hasnt been any while I am not around.
I dont actually have a q tank set up but I have plenty of small tanks that I could set up as one I guess..
What needs to go in there as a basic q tank? I'm not very organised as far as this goes.. guess I should have been. Have you got a med suggestion for me?

 

[melbournefl]

Lindy, you might check out the wonderful FAQ at the beginning of this board. If I remember correctly, Beth put in almost everything you've ever wanted to know about QT tanks.
HTH
Later,
Paul

 

[lindy]

When I got up this morning I found the fish that was hiding being made a meal of by a crab. I didnt have much time to do anything so I took it out and placed it in a container of water so I could check it properly later. When I got home I found the injured one dead but not attacked any further.
I also managed to find 2 crabs, one of which I am certain was eating my fish earlier and a shrimp. I am going to put them in the sump as I dont want them causing any more trouble.
Thank you for directing me to the FAQ's, they have helped my alot, theres so much to read on this message board I get lost!
Lindy