I know you know your stuff so this is probably a dumb question but that pump will be sending air to more than than just that one reservoir right? I use a what I think is the next pump size down from yours for 6+ 5-gallon dwc reservoirs at a time, so yours would probably be overkill for that one tub. My concern is that it will be pumping out too much heat for that amount of water. Good concept though, I have a similar setup with a very small water pump and an aeroponic manifold in a 5-gallon bucket, it holds 5 clones with neoprene collars over holes cut in the lid, also about $40. I tend to see roots start after about 5 days, I'd expect similar results from yours so long as the water doesn't get too hot.