I would never buy an acrylic tank again either. I've got 4 - 10 x 3 x 3 foot all empty.
On these I have used Chinese Algae sucker mouth fish. They are very fast with soft mouths so they can't scratch acrylic and less prone to getting eaten by bigger fish. If the tank is too clean and they aren't fed, they start slime scraping your fish. I prefer the golden morph which are easier to see as they are hard to catch out. Some would get quite big and suitable to clean bigger tanks of predatory fish (1m +)
It's much easier to keep the lights off and not have algae. Once the acrylic has tiny scratches, algae highlights these and anchors.