6 months would be the minimum for 2 reasons. It first shows that you can actually get growth. It second shows that you can keep a tank in decent condition.
I don't think using a controller is fair unless you're budgeting the entire thing in the cost. I have an Apex as well, but I think it would provide a significant competitive advantage being able to run pumps, lighting, ATO, etc. from it when everyone else has to scrap something together. An ATO or even a timer for that matter is a luxury and not a necessity IMO when you're on a budget.