Thanks Joe. Picking up a 10# CO2 tank this week. I have a Red Sea Pro 500 system that I am going to start with. I bought it for the 90 a couple years ago on sale and never got it going. The reviews don't seem favorable though, especially for the diffuser. I may try to make an inline reactor to splice into the return line just after the sump. This would be so much easier to use and keep the clutter out of the main tank. Let me know if anyone has any ideas.