Fish eater

Question
Ok, I have a fish in my tank that is killing or eating other fish. The fish in the tank our not know for killing fish the size of the missing and dead fish. I have a mild behaved Betta, a temper mental red Tailed shark, a Corydora, a Plecostomus who's really big... guppies and I've added 2 algae eating shrimp (gone missing), 2 pea puffers (one missing) and mixed community fishes (not sure the breeds they were label mixed) The last three types are new... but the guppies have been turning up dead or missing for a long time now. I'm hoping that I can pin down the potential killer, and relocate him to another tank. Please if you have any though, it would help. All of the fishes are too big for the betta to be the one killing them.
Please help!
Trista

Answer
Hi Trista,
Wow, sounds like you have a sneaky fish killer!My first guess would be the red tailed shark. I have heard that they can sometimes eat other fish. I had one and never had this happen. Of course he decided to jump out of the tank one night and that didn't work out too well for him. Watch out for that since you really have to have any small space covered on your tank cover or they will find it and jump out.
Could it be that some of your fish got sick and sometimes if a fish dies the other fish will eat them so fast that you never do find any remains of them. Even your pleco might eat a decaying fish. I don't see how your puffer could be doing it. I would think all he could do is just maybe nip a few fins. Bettas usually don't eat fish as large as you have. They would eat a very small fry but not a grown fish. I don't know what the other community fish are or if they could possibly be the killer. Maybe if you could try moving your red tailed shark into a different tank and just see if things calm down a bit and there are no more missing fish.
Here is a website  that I thought you might like to read describing the temperament of the red tailed shark and the possibility that he might be the one that is causing the problem:http://www.aquatic-hobbyist.com/profiles/freshwater/cyprinids/rts.html
I hope you can solve this mystery soon without any more missing fish!
Hope this has helped,
Karen