Help with lights

[Fay]

Hi,
I have Aqaone lights sitting under the house not being use at the moment they have freshwater 36W ATI BR-HG bulbs in them that I used on my freshwater tanks the lights are 48" long and I have two of them with two bulbs in each light, they would run the full lenght of the sump and the screen would be 80" X 9" for a 420 gallon reef.
I would put the lights on the outside of the glass and hang the screens on the inside to water level would these lights be ok to use they are the bigger bulb t8's not t5's

[SantaMonica]

Can't use halogen bulbs at all... too much heat, and it's the worst K for algae. T8's are ok, so just replace the bulbs with T8 2700K

Lighting: Basic rule is 0.5 watts per gallon for medium filtering, or 1.0 watts per gallon for high filtering. You have 420 gallons, but only 36 X 4 = 140 watts. That is only 0.33 watts per gallon. If you are going to stock lightly, and feed lightly, you might be ok. I'll assume you want to just use the lights you have, so we'll stick with 140 watts.

Screen: Basic rule is one square inch per gallon, which would be 420 inches. You have 720. Your lighting is weak as it is... you don't want to spread it even thinner by having a larger screen because weak lighting just produce cyano and wastes your flow. So I would reduce the screen size to 10 X 48, and put two lighting units (total of 4 bulbs) on each side. Then, I'd cut the screen in half vertically, so you can clean one half at a time without bothering the other.

Flow: 48" needs 48 X 35 = 1680 gph. Or, if you want to have redundancy, make two 24" pipes of 840 gph each. If one pipe stops flowing (bad pump), you still have the other to keep thing safe.

Bulb placement: You say you want to put the bulbs on the outside of the sump, shining in. Hopefully the sump is not wide, because the best position of the bulbs is no more than 4" from the screen. If the bulbs are 8" away, your filtering is probably going to be half of what it would have been. And since your lighting is weak already, you might have problems. If you are really going to use those lights, I'd put them inside the sump, right next to the screen, and use an acrylic sheet in front of the bulbs to keep them dry. Truthfully, if you kept those low power bulbs 8" or more away from the screen, I'm not sure I'd build the thing at all; it just too much hassle for little filtering that could easily be overpowered by a large feeding.

[Fay]

OK back to the drawing board not going to use those lights if they don't put out enough light.