Switching from T5 to Metal Halide

[Gryhund]

Among the other issues I've been having with my tank, yesterday half of my T5's stopped working on a 4 bulb fixture. I had hoped it was just a burned bulb (does that even happen??) and switched out all four bulbs with no change.

I dusted off an old 250w metal halide I've had as a backup. The bulb had been used 1-2 months before taking it offline. I know I've forgotten everything I thought I knew about metal halide so I need a fast refresher course.

I've lowered the time the lights will be on from 5 to 4 hours. Do I need to shorten it more, and ramp up to 5 or 6 hours, or is this okay? I'm trying to avoid bleaching or stressing the corals any more then they already are.

I really prefer the blues I get from T5's and would like to find a decent replacement 4 bulb T5 fixture. Any suggestions on that are appreciated, too.

TIA

[AZDesertRat]

Raise the MH fixture if possible to gain distance between the light source and corals. If that is not possible cut some pieces of window screen and stack several together to make a light filter. Over the next couple of weeks remove one screen at a time to acclimate the corals to the more intense lighting.

You might check the wiring in the end caps or your T-5 fixture, most have stab connections and maybe one wire has come loose breaking the circuit. This used to happen with my old VHO fluorescents sometimes when I moved the canopy or lid.
If you don't need a complete new fixture you might look at the DIY ballasts and end caps at Hellolights and mount them in what you have.

[Gryhund]

Thank you!

Not having to replace the whole fixture would be nice. I'll take apart what I have (an old Finnex T5 fixture) and see what we can see. I usually actively avoid DIY if it involves electricity, but will make an exception for the tank.

[Gryhund]

I had forgotten I know a young electrician! He was nice enough to take it apart and test all the guts.

One of the ballasts needs replacing. It is a two ballast fixture. Any opinion on whether I should replace both ballasts or just the bad one? His opinion was just fix what wasn't working....

[Poseidon]

I'd replace both, since you have it apart.