How many LED's do I really need?


Reefing newb
I've got a used 55 gallon (48" long) tank that came with the standard 2 bulb hood light (2x24" bulbs). I'm guessing that this isn't really the best choice for saltwater fish, and it doesn't leave room right now for a night light option,so I've been looking at various LED DIY kits. The problem I'm finding is figuring out just how many total LED bulbs I'd need for this kind of tank and what combination I need (whites/blues/reds). the kits seem to be grouped (6, 12, etc.) with no tank size reccomendations.

My intention is to make a nice wooden hood to enclose all the lighting parts, and I'm really only looking at a fish and live rock tank for now. I'll think about spending money on corals once I know I can keep the fish alive past the guarantee date.

I'd love to be able to drop $400 and be done with it, but that kind of money isn't an option right now for just the light. I was considering keeping the fluorescent and adding another set of bulbs that could be used for the night light, but the LED's sound like they'd be cheaper to run and last a LOT longer to boot.
So, does anyone have any suggestions on the number of LED's needed for a tank this size?
I have a 20 gallon Kent Marine. It has 6 white LEDs and 4 Blue LEDs, So far I have never had to use the fluorescents and everything still grows. The tank runs at approximately 30watts.

Maybe you can work out what you need from the above in relation to your 55g?
if you are looking into just doing a fish only system, you really don't need to worry about high end lighting yet. i would say if you replace those lights with a Flourescent with a white spectrum it will work just fine. MH/T5/led are mainly for coral growth. that is something you may be able to save for while your system is fish only and get a better syste, when you are ready.
You only need more powerful lights if you plan on keeping corals/anemones/clams/other photosynthetic animals. You can use any lights you want for fish. :)