Building my own hood with lighting for 20 gal.

[Billsgate]

I'll be building a hood for my 20 gal in the next few weeks.
dimensions of tank are 23.6 inches long and 11.8 inches wide. I'm thinking of putting 3 15W NO fluorescent tubes in there. My plan is to build a seperate compartiment in the hood for the ballasts. I think I'll need to buy 2 ballasts, 1 for 2 tubes and 1 for 1, correct? They will sit on top of the actual lights, seperated by 0.4 inch thick wood.
Do you think I'll need to build in fans in the hood to cool down the ballasts?? And the 3x15w NO fluorescent tubes, will they also need cooling down?

I've already drawn out a hood design, I'll try to get that online in a few days.
For fans I would install a computer power supply in the same compartiment as the ballasts, installing a fan on each side of that compartiment. This compartiment will be accesible through a lid I can open with a set of hinges. measurements of compartiment: 23.6inch x 7.8inch x 3.15 inch.

So anyone have an idea what cooling I'll be needing?

 

[dskidmore]

The number of ballasts required depends on the type of ballast. An Ice Cap 430 ballast can support up to four 2' bulbs by itself, others may only support one.

Cooling the ballast and bulbs would be a good idea. Some sort of vent holes at the very least, a fan would be better. Heat decreases the life span of the bulbs and may heat up your aquarium too much. The ballast will create more heat than the bulbs, so focus your cooling efforts there. If you could construct in such a way to pull air from over the bulbs through the ballast compartment, then vent the air, you could cool both compartments with minimal fans. If these was a VHO setup, I'd lean more towards seperate air flows.

My current system has two shop lights (two bulbs per shop light) in a basic 5 sided box. It does ok without cooling, but I don't expect my bulbs too long. The metal casing also conducts some heat away from the ballast.

 

[czcz]

You might want to consider running two tubes 2x ODNO, so you get the outbut of three bulbs. I have no first hand experience but there's a lot of info in this forum and Planted. It also appears relatively easy to later increase the overdrive factor for more light.