disappearing fish

Question
I have a 45 gallon aquarium and have been working slowly to fill it. My efforts have been dashed, however, as my fish have been disappearing. I started out with quite a few from petsmart but one by one, they died. What I had left had been living together peacefully since December. I had a large pleco, a cory catfish, 2 tiger barbs, a fairly large dalmation molly and a large kissing gourami. Last week I realized the gourami was dying. Upon further investigation, I saw it no longer had a tail fin. I left it in the tank and in the morning its eyes and some of its body had been consumed. Sad day. Then yesterday morning I couldn't find my molly. It had disappeared. Then this morning the smaller of my 2 tiger barbs was gone. All that's left is my pleco, catfish and tiger barb. Who's eating my fish?!

Answer
Tiger Barb. Tiger barbs are very aggressive and should be housed in a species only tank. They'll kill fish without a proper school of at least 8+. They are not meant for community tanks.

Common Pleco's need a 100+ tank.
Kissing Gourami need 75g.
Cory Catfish need 6+ schools.
Tiger Barbs need 8+ schools.
Mollies need 3+ groups.