Never heard of it, But I do know that marine Stonefish (maybe you got a Brackish variety) are extremely toxic and can kill you and any tank inhabitants it comes in contact with. They also get fairly large.
Sorry I don't know too much about it though, I would suggest you go back to the LFS and ask what they have sold you is realy called (Scientific name) or give us a picture of it and we could help a little more.
There are F/W Stonefish but most of the stonefish are brackish or saltwter but they live in estuarys so they will be survive in F/W but they will not be healthy. I hope yours is the FW variety and they are usually called Monster Fish