40watt for a 15gal

[Petah]

Ok here is my set up. tall 15gal tank with 3 inches of play ground sand with inbedded hydro baskets (4 inch). with a carpet of thick, full 1inch of extreamly heathly java moss. Plants for the baskets do not know. just yet.... My question; i just made a 40watt lght set up from 2 hagan 20watt hoods. and i was wondering if i do not use c02 needing plants like my javamoss and some ferns etc..... will 40 watts be too much? will i get an alga bloom? (side note i play paint ball so i retro fitted an old paint ball gun for a diy co2 system which works quite well.. able to set my bubbles from 1 a sec to 1 every 5 sec) will i need this co2?

[AquaObsession]

For a 20G, then ur wpg will be 2... which is okay (if not inadequate)