Thx for the input everyone. The reason I'm keeping the water level low is that the desk it's sitting on isn't that stable. I plan to move in a few months and will get a stand for it, and fill the tank all the way.
So far there are about 20 guppies, 10 rasbora, 5 cherry barbs, 1 panda cory, and a algae eating guy.
I bought all the materials to build a DIY co2, just have to put it together and also find a check vavle. Didn't see one at the petco I was at, maybe I'll try a different one.
More pics later, I'm not at home at the moment.