If you have phosphates in your water(like I do here in Spokane), I have found that you're more likely to have algae problems. To help keep it in check, I have found that aponogeton bulbs grow very fast and out compete the algae. In mature tank water, some varieties grow so fast that you can see a difference in amount of growth 2 to 3 hours after they first sprout.
And yes, fish food is an excellent source of ammonia.