It sounds like you've got (potentially) great lighting, but low Co2 (for your tank size), and you completely lack ferts.
This is a recipe for both algae, and plants that don't get their red on.
Root tabs are your easiest solution for ferts (for root feeding plants), and dry ferts are your best value by far for water column dosing. The paintball Co2 method will technically work fine, but the tanks are very small, and in the long run will probably cost more to frequently replace over and over, than spending $100-150 for a cheap 5lb Co2 tank setup and only having to refill/exchange it every few months.
This is a recipe for both algae, and plants that don't get their red on.
Root tabs are your easiest solution for ferts (for root feeding plants), and dry ferts are your best value by far for water column dosing. The paintball Co2 method will technically work fine, but the tanks are very small, and in the long run will probably cost more to frequently replace over and over, than spending $100-150 for a cheap 5lb Co2 tank setup and only having to refill/exchange it every few months.