is there a differance between metal halide n just halide? i can get them cheap through work fitting n all and globes up to 500W i think it is, is there a differance between metal halide and just halide? differant ballast or somthing? dont know to much about em just that there good to have for corals n stuff...think i need em since i got some 'live rock' for 12.90 a kg and then the guy said that what was in the live rock was actually a 200 dollar coral but he gave it to me cause the sign was there and it was where it shouldnt n i think i need to upgrade my lights...at the end he said that some corals must of been put there by mistake and i got about 500 bucks worth of them for the price of 15kg of live rock which i purchased today. so if anyone could give me an explination between the differances id be really appreciative thanks.hope to find a camera so i can show off my 6 hour work i did today on remodeling my entire aquarium!