All of my reservoirs are exactly like that. Works great and if you need to recut or get new, big deal.
You need more of a cleaning crew than a couple snails. I would add a half dozen turbo, at least that many cerith, and a dozen nassarius. In a lot of ways the algae cycle is much worse than waiting on a good solid nitrogen cycle. It takes a good amount of time to build up the right algae in the right amounts. Crabs are generally better for hair algae but all crustaceans are opportunists and will eat the snails whenever they can. Personally I would ditch the bio-balls, live rock should be enough biological filtration. At the moment I've got nothing in my inTank aside from rubble and foam. I do however have an UV filter in line and use a hang on back with activated charcoal occasionally to polish water occasionally. If you are going to skim, the Tunze is a much better option. Have you tested calcium? Once coralline gets a good start it will help to outcompete the nuisance algae. As with the nitrogen cycle, patience is key. It takes a while for a tank to balance and harden. You're off to a good start based on the ATO alone.
Happy reef keeping