How long do you leave your Metal Halide on?

[Regric25]

Lets hear it. I have read so many different recommendations for how long to run MH lights for a reef tank. How long do you run your lights for? If you could include the wattage, color temp, and if its a reef tank or a FOWLR tank. Thanks!

[Mr Cob]

Reef tank

-2 x 250w MH 14k, run from 4pm-11pm = 7 hours
-2 x 460nm Blue Leds PowerBrite modules, run from 11am-3am = 16hours
-1 x Refugium flood light 90w, run from 1am-9am = 8hours

Tank currently stays at 77 degrees when no lights are on, 78 degrees while fuge light is on and 79 when MH turns off. I used to run the MH for 8 hours and I would hit 80 degrees. I also run a fan over the fuge when the MH is on.

There's no secrets here, pick a time and adjust up or down in half hour increments every couple of days until you get what you like. I also had unwanted algae growth with 8 hour MH cycle...cut it back to 7 and that helped. I've been thinking about dropping it to 6 or 6.5 too.

[Kristy]

Small tank (20g hex reef):
150w MH, don't remember the k, ~9 hrs / day

Big tank (210g reef):
2 x 250w MH w/ 12k Reeflux bulbs, ~7 hrs / day
(also run 6 bulbs of T5s ~14 hrs / day!)

[kkiel02]

I have 2 250w 20k that are a year+ old so they stay on for 10 hours. I would replace the bulbs but am getting new fixtures for the new tank.

[Regric25]

I just want to make sure im not over running my lights. I have a 100 gallon tank 48x24x20tall and I run 2 250w DE 20k XM mh 8 hrs a day. I dont see a big temp swing durring the day probably because I keep the cieling fan on all day long. I dont use any supplemental lighting at all with it. The only lights I use other than this is my fuge light at night after display lights go out.

[txav8r]

2x 250MH 14 k for 8 hours on a 75 gal tank

[secretweapons22]

1X 150MH 20K 4 hours a day on a 30 Cube

[d3rryc]

2 x 250MH 10k for 10 hrs on a 140 gal