The rule of thumg is 1 watt per gallon. So a 16 watt pump would cover. You can get them to survive with a half watt a gal but not as cool. What would be awesome would be a 40 watt pump. 50 bucks or so, check craiglist.
But if you also want the bubble action to be enoughto water plants until roots are in the water per the link below then one of the above to each res, and 3 or 4 12 inch airstones for each.
But if you also want the bubble action to be enoughto water plants until roots are in the water per the link below then one of the above to each res, and 3 or 4 12 inch airstones for each.
Maybe and you could go to 2 stones and one pump when roots are well into the water. But it would be more hassle than it was worth IMO, and you need the extra bubble power in the beginning. Either way it's easier than pulling a water pump and tubes. Also, when you have two pumps, you always have a backup just in case.