other things to improve skimmate production... the internal horizontal overflow (do a keyword search or peep the illustration in my Book of Coral Propagation). Instead of having 2, 3 or more holes (back wall drilled tanks) directly drawing say the top half inch of water off the surface (or worse! those awful internal towers with floor drilled holes where all water overflows a narrow weir)... the long horizontal overflow stretches that same flow out over the length of the dam... allowing you to capture "thinner" surface water that is more concentrated (proteins).
Also... bubble size and air flow is everything. Most skimmers can tolerate a wide range of water flow, but few do well with weak airflow or large bubble size. Some skimmers can be boosted by adding a strong pressure rated airpump. Or... cheap venturi valves can be improved by adding a precison needle (air) valve to the intake.
FWIW
