Anyone familiar with Cow fish

[sully08]

I always liked the look of the cow fish. I bought one from a local fs. He was in really good shape when I put him in quarantine. He sat in there for about 11 days eating everything I gave him and very active. I woke up one morning and he was dead on the bottom, no signs the night before of any distress. Just when I thought everything was going good. I had 2 small chromis in with him, they are doing fine. I don't know if he released any toxins into the water, I performed a 50% W/C anyways. All water tests were O.K. Loved his personality. Any ideas?