Watts per gallon isn't an accurate rule, especially when it comes to LEDs b/c they have a lower wattage than MH
and T5 HO
etc, but they penetrate through the water really good. My lfs
got LEDs and they say they only have them on 50% and sometimes it's too much for even the SPS
. Check the par rating. Don't know many LEDs or have personal experience with them. I know ecoxotic, ecotech, and aquasol are great companies that have high quality LEDs, but they are really expensive and prob. won't fit in your budget.