Wow you spent quite a bit already on the CO2 system. 
My plan is to kill them by blacking out, then do some experiments:
1. back to 2.5wpg + CO2
2. lower to 1.5wpg and no CO2
I'm gonna go with which ever one results in lower algae growth. I really don't want to start fertilizing tanks and no pressured CO2 for me.

My plan is to kill them by blacking out, then do some experiments:
1. back to 2.5wpg + CO2
2. lower to 1.5wpg and no CO2
I'm gonna go with which ever one results in lower algae growth. I really don't want to start fertilizing tanks and no pressured CO2 for me.
