Heres a post by Lion_Crazz under the New Hobbyist>101 tips...
10. FLOW IS KEY IN KEEPING A HEALTHY TANK. Having adequate amounts of flow in your tank will largely determine how clean your tank stays. If you do not have enough flow to keep the water movement and to prevent dead spots, you will deal with algae issues, detritus and debris build-up, and nitrate issues. Shoot for at least 15 times the turnover of your tank volume per hour, but preferably, 20 times. This means that if you have a 55 gallon aquarium, you want to be turning it over 55 times 20, which equals 1100 gallons per hour coming from your filter, powerheads, skimmer, etc. Anyone with a larger tank or who does not like the look of powerheads should consider running a closed loop (which is very simple to set up).
I would say for a 34 gallons it would be 680 gph. But i have a K1 and a K2 ph with the stock ph's that put out 290 gph and i just point them towards the surface and let the K1 and K2 handle the back and front.
What's the stock ph's gph?