OK, we have 4 cats. 2 are my sisters and 2 are my mothers. 1 of my sisters cats started losing weight a few months ago and when she took it too the vet and he said allergies or stress. Well he is now starting to get back to normal. Now my moms cat is starting to lose weight. What is going on here? I was wondering if it has anything to do with saltwater. I have a 30 gallon reef tank with a 10 gallon sump underneath. Most of the time they do not bother it as far as I know. Who knows what they do at night. A little bit ago he (the one losing weight) tried to get under there and I caught him. Now, if he is getting in there at night and drinking the saltwater, will this cause him to lose weight?