please help!

[laurahammock]

My sister in law has a tank with a small catfish, an "algea eater" and a small crab. For decoration, she has a small sunken ship and a skull and a couple of plastic plants. All of a sudden her beloved catfish--she LOVES it-- what look like gash marks! One side looks like a long slice and another is smaller. A few days ago, she had another catfish that died, I think it was ich; she said it had white spots on it and she treated the tank twice, but it still died. Does this sound like a bacterial infection, or is it possible that the crab is doing this? About a month ago, she saw the crab pinching her other catfish, but could it make this kind of gash? I also don't think it's from the decorations--they don't have any sharp edges. Any response would be great since she's very worried about her fish.
Laura

 

[MissFishy]

What kind of crab is this? How big is the tank? Usually no catfish should be kept in a tank where crabs/crayfish/shrimp are kept as they will pick at them since they are both bottom dwellers. Crabs/crayfish are scavengers and will pick at anything lying around the bottom of a tank...i.e. a sleeping catfish.

 

[laurahammock]

She has a fiddler crab....she is not very fond of it, so she's thinking of asking the petstore if she can "donate" it back! We asked the store owner for some suggestions and she gave us some medicne that treats ulcers and wounds. I hope it works. Thanks for the info--that does make sense!