Well, I think it's a good idea to keep metal away from the tank anyway. Though I don't think metal rust causes phosphates since rust is only FeO2 or something to that extent. However, I say use hose clamps since you can adjust them with just a screwdriver, instead of just clipping off a whole zip tie, and using a new one. Might as well invest in a couple of bucks for the hose clamp.