Cutting down a couple 48" T5 fixtures...

[Mole]

to make some 36" fixtures. All I need is the overall length of a 36" bulb. Thanks

 

[Reefing Madness]

Remove from fixture. Remove bulb ends, cut reflectors to your liking, buy new ballasts for the 36" lamps, retro the light back into the canopy. Done.

 

[Mole]

I should be able to use the same ballasts no? Won't the ballasts only let through what power the bulbs will draw?

 

[trido]

I should be able to use the same ballasts no? Won't the ballasts only let through what power the bulbs will draw?

It depends on the brand of ballast. A lot of ballasts will overdrive the bulbs causing them to burn hotter and wear out faster.

For example I used an icecap 660 on a four bulb 36" configuration over a frag tank. Sure it worked but the occasional bulb would burn out after only five months. That ballast would be better suited for a four bulb 48-60" configuration.

The same goes for the Fulman Workhorse series of ballasts. You should use a workhorse 5 instead of a workhorse 7 or 9 for most 36" applications.

 

[Reefing Madness]

If its the ballast that came with the unit, no you can't use it, it will overdrive the lamps.
Like stated above, a Workhorse Ballast has a range it will utilize, and not overdrive the lamps.

 

[Mole]

Gotcha... Thanks