I don't know what the problem would be with the gramma ... but I'm about to find out, as I'll be introducing one to my DT (with a firefish and a target mandarin) this afternoon. I've got a pair of yellow watchman (prawn) gobies who haven't met yet - they will today. She's been over a month in QT with a 0" sandbed, and seems to be fine. My pistol keeps to himself in his hole, and never bothers anyone, except for popping at any bumbling hermit that strays too close. They lumber away, and that's that. ~Bruce P.S. - Welcome to Reef2Reef, Benj! Hope you find it as enjoyable as I have.