Dead Mr. Fishy

Poor Mr. Fishy has joined fishy heaven in the sewer this week. I can't figure out what wrong. I had just changed his water that morning and I can only figure something got in the water that did not set well with him. I was walking by and took my usual look at him and he was at the bottom of his bowl floating straight up. I felt horrible and the kids just thought it was cool that we flushed him down the toilet.