i have a community tank that has been growing in plant size, it has two java ferns, one unknown another unknown and two banana plants, i have been wondering now that i want more plants will i need supplements or co2 to keep my plants healthy?
No, you do not need CO2 to keep your plants healthy. It's perfectly viable to have a non-CO2 tank. You'll want to keep your lighting low to prevent algae, and dose light ferts only occasionally (once every week or once every two weeks). If you only have five plants right now and are just going to add only a few more, you probably don't need to dose anything if your plants are doing fine as is.