First, welcome to Fish Lore
If you don't have any algae problems, you don't have to get an algae eater. Once you start getting algae, you can get an algae eater so that you don't have to clean the algae yourself. But as JP said, do provide it with a good diet. A good algae eater for a tank of your size would be 1 Bristlenose Catfish, or 1 Siamese Flying Fox (Crossocheilus Siamensis is the true Siamese Flying Fox, so be careful not to confuse it with other similarly looking species). Or, you could get a few Otos.
As for water aeration, unless your filter(s) don't provide enough water movement and circulation, you don't have to have any airstones. However, even though my Aqua Clear 70 power filter provides excellent water movement and circulation in my 30 gallon tank, I still run an airstone there. I don't think water movement is a problem in smaller tanks. But when you have a large tank, I think it's necessary that you have some kind of additional areration there, especially if you have only one filter at one end of the tank. In large tanks, one filter only is not likely to circulate water well. In large tanks, a powerhead at the other end of the tank is useful. Or, instead, having two filters - one at each end of the tank.
P.S. In my 10 gallon tank, I have a Whisper Tetra 10 filter, and it does not provide good aeration and water movement in my opinion (it's not a very good filter at all in my opinion). So I run a good airstone there, at the other end of the tank - it helps aeration and water movement.