Thanks, Karla, Jordi and Greenfinger2!
Jordi, you spot the scheme!
One more detail, on the top (which is the main filter) the are 2 outlets.
Thinner tubes for giving a bit stronger flow and they can be ajust [left-right] and [surface or substrate]!
I can easily configure the flow direction to adjust some evaporation or maintenance (is very useful)!
The big pipe below is now consensual... I believe that i use 1/2 to 1/4 of the Co2 with this configuration.
Finally found the scissors!

Maybe tomorrow another picture...

cheers!