Well I'm not exactly sure what your question was. But the wpg rule is a myth so 20w to 20g does not tell us how much light you have. You also don't mention what method you use to diffuse your co2, or what ppm your co2 is at. Another thing you mentioned was splitting the co2 line too two tanks? That won't work you need a needle valve for each tank so you can properly adjust to the right amount. You can buy a manifold to do this.
We need to know:
What your question is?
Sent from my iPhone using Tapatalk