parasite infection?

Question
I have a 29 gallon freshwater tank and everyday I find another fish dead!
They include Kribensis, gourami, redtip tetra, siler hatchet, and several catfish.

Ammonia and nitrite levels are undetectable and ph is at 7.0 General Hardness is 10 ppm.

The fish that die do not appear sick the night before. When I find them dead, the anus appears red so I'm thinking internal parasites?

Can you please suggest the best treatment?
Thank you!

Answer
Maggie,

I'm sorry but you don't provide me with enough information to diagnose disease.  This process is difficult at best with tropicals, and misdiagnosis could cause even more problems.  The first thing you should do is add an aerator and do a 30% water change.  Most fish deaths are caused by problems with water chemistry and often insufficient oxygen can be a serious contributing factor.  Let me know if this stops your fish death.

Michael J.