[bonsai411]

I have a 90 Gal. tank housing fish, inverts, corals, live rock. I use 2/175 watts metal halides (13k), and 2/96 watts compact fluorescents (blue).

How long should I keep the MH on for? And, how long should I keep the CF's on for?

Also, I notice, the water temperature goes up to 80.5 F after a few hours witht eh halides on. This is almost a 3 degree rise from my normal 77.7 - 78 degree average without light. Is this okay?

Mike

[charlie]

I run my halides 9 hrs. and my vho actinics 12hrs. As for the heat problem, if you have a sump, you could get a clip on fan and direct it at the surface of the water. I have a little 5" fan on my sump that comes on and goes off with the lites. Ever since I put the fan on there, my temps never get above 81. HTH

[saltjunkie]

i have my actinics on for around 10 hours... my mh on for about 5 or 6....

my mh's keep my temp up in the high 80's... 84-86... so i keep my heater on 85 just to keep it all stable.. im not saying this is the correct way.. but has worked for me for many years!!!!!

[Reefland]

A period of 12 on and 12 off is a good setting, some people go for 14 and 10; anywhere between those will be fine. This would be for your Power Compacts.

The length your halides can be on will depend on your tank temperature; if it's not a problem then having your halides on 1 hour after and going off 1 hour before your PC's would be great. If heat becomes a problem, adjust the MH period accordingly.

[Ninong]

Originally Posted by bonsai411

How long should I keep the MH on for? And, how long should I keep the CF's on for?

If you wish to duplicate natural conditions in the tropics, you should keep your lights on for a total of 12 hrs. That means the actinics would be on for 12 hrs and the metal halides for 10 hrs.

You could boost that up a bit to increase growth, keeping the actinics on for 13-13.5 hrs/day and the halides on for 11-12 hrs/day.

Also, I notice, the water temperature goes up to 80.5 F after a few hours witht eh halides on. This is almost a 3 degree rise from my normal 77.7 - 78 degree average without light. Is this okay?

The 80.5 degrees Fahrenheit water temperature is OK but it is always better to maintain the water temperature in a tight daily range. A daily range of 3 degrees F is acceptable but a range of 2 degrees F would be better. Obviously a daily range of less than 2 degrees F would be better still. All of this is fine but usually not possible in the Gulf South unless you have a chiller. You may find that increasing your lighting photoperiod causes an even wider swing in your daily temperature range, necessitating a reduction in the lighting period to avoid overheating issues.

[golfish]

I've learned that its best to start out with a shorter light period with new bulbs and increase as they get older. I run my Radiums 6 hrs a day at the start and increase 1 hr every month until the end of the 6 month then I replace the bulbs and start over.

[gopsal]

I had the same problem with temperature ranging from 76-82 when I first started cycling my tank. I purchased two small computer fans and installed them to remove heat. Worked perfectly and the temp stays at 76-77 now.