Thank you, the article is really helpful! I'm going to set the diffuser near the HOB so hopefully it can diffuse better within the tank. Right now, the diffuser only causes bubbles to rise to the surface above some plants, so I think moving it near the HOB should help.-Mak- said:Not stupid at all, and quite important! Simply put, there just needs to be a way for water to circulate, disperse CO2, and allow for proper gaseous exchange. On a small tank a HOB can do this quite well, on larger tanks people like to use lily pipes and powerheads. The goal is to send CO2 to every plant while getting the right amount of surface agitation not to drive out CO2 but still allow some to leave and oxygen to enter.