I do the line game with my diy co2. run one tube from bottle #1 into bottle #2. This line, for me, is below the water level in bottle #2. run another line from bottle #2 to you bottle with just water. then another line from water bottle to tank.
this way I can somewhat gauge what each bottle is producing.
really reducing organics seemed to help control algae in my tank.
20L Daughter's Tank: 2 Bolivian Rams and Threadfin Rainbowfish
40B Inlaws Tank: 4 Bolivian Rams and Guppies
75 Main Tank w/ sump: 5 Glossolepis pseudoincisus, 5 Melanotaenia boesemani, 10 Melanotaenia praecox, 5 Melanotaenia lacustris