Welp the more and more i think about replacing my MH bulbs as its getting to be that time again... i've been thinking about putting the money i would spend on the bulbs into investing into a DIY LED build.

I just wanna figure out first, how many LED's ill need. I've heard between 48-72.

My tank is a 90g 24" tall, and i plan on hanging the LED's about a foot above the water.
I have a mixed reef sps/lps, SPS mainly mid tank/to a lil higher.

What size heat sink?

i've been thinking about going cool white, neutral white, and royal blue mix. 2:1:1 (RB,CW,NW)

I also think i might need lenses.. though i dunno what kinda spacing im going with yet as this is just in the initial pricing planning stage.