I can feel your pain and I am sorry for your loss. Two and a half years ago my wife and I had to put down both of our 10 year old dogs about 6 months apart. Just as we were starting to get over the death of one we had to put the other down. I was devastated. I did not have fish tanks at the time but I do think it would have helped. One thing that one of my friends sent me that I did find solice in was this poem. I dont know if you have seen it before but I believe in it.
Rainbow Bridge Poem Our lost pets are happy and healthy now and we will see them again. Keep your chin up and know that you will see the big goober again!