I experimented with gravity feeding my recirc skimmer. I gave up after running into problems reestablishing drain siphon in enough time to avoid a tank overflow, after cutting-off/restarting the return pump (daily feeding and power outages both). The closed end of the drain (into the skimmer) would provide enough backpressure to impede siphon regain, resulting in a tank overflow.
I'm sure with a bit of effort I could have overcome the problem (by venting the drain at the right place, over the sump so water surges out of the vent hit the sump instead of the floor) but it wasn't worth it. I just use an MJ400 to feed my skimmer now, it's small, quiet and efficient. Anyways, something to keep in mind.