Saltwater Tank and Septic System

[Myka]

How big is your aquarium? I don't know much about septic systems, but I think you would need a fair amount of salt in the system before it would affect the concrete. Does your system get pumped out or does it go into a septic field? Is it a plastic septic tank or concrete? I would probably talk to a septic guru.

The bacteria definitely doesn't matter - bacteria adapt easily from salt to fresh to salt.