150w of MH over a 36 bow is way to much light even if your using press. co2. you really dont need a ton of light to grow plants, whats more important is ferts and co2. not many people use MH on a FW tank for good reason... its total overkill. the less ligh you have the more managable your aquarium will be, the more light u add makes the balancing act with co2 and ferts a razors edge.
150w MH would be good to grow coral, but not FW plants.
for a 36 bow i would go with 1 T5HO dual bulb fixture. with that you should be able to grow just about anything.