HPS gets hot I wouldn't recommend using one in such a closed space. Don't put all 15 seeds in there definatly not enough space in there I'd say you might be able to fit two and you should go with floros in my opinion unless you get a bigger space. Also try and get circulation in there and a fan blowing constantly on the plants (it helps a LOT). Goodluck and keep us posted we wanna hear how things turn out for you.