Whether it will be sufficient for corals greatly depends on the depth of the tank and the types of corals you're wanting to keep. 4x t5ho is sufficient for a lot of corals in general, but the difference in a shallow tank and a deep tank is pretty big in terms of what you can keep lower down. For replacement bulbs, I'd look in to ATI. I have one of each - blue plus, coral plus, purple plus, aquablue special. The color combo is really up to you. My tank is blue, but not so blue that everything gets washed out.
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