In a tank that size, I dont think you even need a skimmer...

Its all in the water changes in my opinion. 1g per week is good enough with a low stocking level, 2g per week if you plan to add a bit more fish and also make sure you test you tank water and the new water every time you do a water change and make sure they are the same.

I think thats what I would do.

Also, In addition to your water changes, make sure that you keep up with eveporation (top-off often) because your water chemistry can shift very easily in such a small amount of water.