Bpm for 29g planted?

[spit.fire]

how many bubbles per minute through an air stone for a 29 gallon tank thats moderatly planted, dual ho t5's, silica sand for substrate, no ferts, and 8 guppies, 5 cories, and a pleco

[neven]

currently i have mine set at 2.5 bps, i also found using a chop stick chunk in an airline tube gives a much finer bubble size that can be swept up by the tank current