oo, one more thing. here we are talking about PCs, not metal halides. 260 watts of PCs are 4x65 watt bulbs. if you have those layed out across a 210 or osmething that big, one then the next then the next, you cuoldnt keep much at all. But if you had all 4 rudding the depth of the tank. if they were all layed next to eachother like a perosn on a bed, then it will provide the same amount of light, but it will be concentrated to a smaller area. so more light will be given off.
but i do agree that MHs are needed for the long term health