No, it wouldn't fry the fishes. Metal halides are better for growing aquatic photsynthetic organisms (corals, anemones, plants, algaes) because they're so much stronger in the blue end of the spectrum (the light that penetrates water best, easiest, deepest, strongest). I would not, however, want to add the fertilizers used for hydroponic growing to an aquarium, I'd be careful of that, as much because I know little about it as much as I do know what excess nutrient levels, especially nitrogenous wastes, can do to fish.