Short Photoperiod

[cephalotus]

I recently switched to metal halides and was wondering what the shortest light cycle reccomended. I know Trop is in a greenhouse but the tank by the register does not get natural light, and they only run their lights like six to seven hours.

[tazzy695]

typically you hear of halides running 4 to 8 hours depending on par bulb type and what kind of supplemental lighting is provided

when I had halides I ran them for 5 or 6 hours and ran my actinic t5ho lights for 12

[Argent]

Hrm - I run my 70w MH for like 12 hours/day

[Sir Patrick]

I agree w/ tazzy. Lets hear some more info on the lighting of the tank, and we can help w/ more info.

[schminksbro]

I run my halides 6 hours a day and my actinics 10 hours a day. Corals can become saturated with light. At that point they cease to benefit and can actually be stressed from over exposure.

[thefishgirl]

My MH are on a timer. Basically 10 on / 14 off.

[Argent]

Hrm - perhaps I need to shorten my photo period - I don't have any actinic supplementation though

[cephalotus]

2 250 watt 20k no supplemental light on a 55 gallon. I shortened my photoperiod from eight hours to five hours when I recently switched from vho. Everything seems to be fine. My energy bill would like to keep it at five hours. The room the tank is in gets alot of sunlight so the fish dont have a problem.

[tazzy695]

sounds like you have way more then enough light and 5 hours sounds good on that system