Trying to find the right bulbs

[Mytinysea]

Thoughts about this bulb and how large of a screen it would cover?

http://www.ebay.com/itm/PAR38-12-Wat...-/110645822782

[Mytinysea]

Or these.... The 20 or 30 watt ?

I'm trying to size for a 500 gph return line with 4 cubes+ and close to 450 gallon total water volume.

http://www.ebay.com/itm/230950111502...634.m570.l4456

[SantaMonica]

The shape of the second one is better to spread the light; some other types are even better because they have multiple chips instead of one:
http://algaescrubber.net/forums/show...-led-grow-bulb

The people that have used these types of light seem to put the lights about 6 to 8" away on a 12 X 12" screen. This would handle your return, and need at least a 10 w LED on each side for a new tank, or 15-20 w LED on each side for high nutrients.