STU801, Your thought of laying the pipe makes one think that by covering large areas with rising bubbles would be better. In theory it even might be but the reality is that it won't do very well. The holes drilled into the pipe will be far larger than those in a membrane disc diffuser and require an impractical amout of air volume. Also, only a tiny fraction of gasses are exchanged as the bubbles lift. The bubbles reaching the surface and then popping, breaks the water tension barrier and allows the gas exchange.

Using a Vertex membrane diffuser with .5 mm laser cut slits will produce a far greater amount of water lifted than an equal amount of air flow though pipes. Even the inexpensive Flexair membrane with 1 mm holes will vastly outperform the pipes.