how long should i keep my mh on

[egos4life]

I have a 72 gall bow front i just picked up with just mh no supplement lighting... They are 250 mh I was wondering how long exactly should i run them... i have the screen to acclimate my corals but just running mh how long can i keep them on

 

[RokleM]

You won't find any one exact answer honestly. Some go as low as 3 hours, some up towards 12 hours. Most seem to believe 6-8 hours is the "good enough" spot where growth will be maximized without wasting electricity and causing heat.

 

[egos4life]

just running the mh i think i would need to run it a 8-10 just for viewing until i can get some supplement lighting... tahnks for your response

 

[sedor]

I run mine for 8 and haven't had any problems. I work during the day so I set my timers to cut the lights on at 4, then by around 5:30 when I get home my corals are nice and extended. They cut off around 12.

 

[mfinn]

My mh's are on 9 hours a day.

 

[michael.lemke]

I am doing 6.5 hours on my 40... any longer seems to burn corals near the top. I do see good growth.

 

[Toddrtrex]

There have been some threads in the SPS forum that shorter photo-periods will increase the growth and provide better colors. I know that when I dropped from 10 to 6 hours for my MH, I noticed that.

But, since you are only going to have MH, and no supplemental you might want to run it a bit longer --- just so you can see the tank more. I would at least skew the photo-period to when you are at home the most.

 

[transd]

mine are on 6 hours a day... 6pm-12am. my actnics go on one hour prior to the halides coming on and one hour after it shuts off

 

[FLKnifemaker]

In my 90 I run my single 250 for 9 hours. My LED's come on a half hour before and go off a half hour after the MH. I have blue LEDs that stay on all night. My sump light goes on/off opposite the MH.