I currently have a 5000 gal pond. I sealed it with black rubber ( HUGE MISTAKE). I somehow convinced my wife to let me build a 10K gal. pond in my basement. It will be concrete with windows....similar to my current pond. However, I do not want to use the rubber. Can I just keep in concrete? Should I try to cure the concrete differently? Can I put either fiberglass or gunnite? Any suggestions would be appreciated. Thanks