well I went cheep and picked up a timer that has 15 min intervals, so would 15 on and 30 off be too much off time the only reason I ask is because 15 on and 15 off is allot of "off and on" that the pump is going to be doing and I don't know how long the pump would hold out ?? right now I have it on 15 on adn 15 off but if I could stretch it out a bit that would be nice...