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View Full Version : 760 watts on a 75g?


Sregnar35
02/27/2008, 06:56 PM
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Hello, I recently upgraded my 75 gallon with better lights. I'm going from 260w power compacts to 760w power compacts and halides. Anyone have experience with this much light in a tank this size? I've already begun moving my coral lower in the tank, and I plan to short cycle the new lights when they arrive. Also, what sort of temperature issue will I have? Currently there are 4x65w pc's, I'll basically be adding 2x250w halides to that. The lights are in a pre-assembled strip with legs, so it will probably be about 4 inches from the surface of the water. My water is 77.5 and 76.5 at night.

MSU Fan
02/27/2008, 07:14 PM
Well, you can probably anticipate the water temp to go up. I have 2 175w MHs over my 75g, 8" off the water and the temp rose.

Also, you got a couple of choices. You'll probably need to limit to the hours the lights are on for a couple of weeks so you don't burn your corals. Also, if possible, place some screening over your tank to limit he amount of light that gets into the tank

photobret
02/27/2008, 07:18 PM
Big time temp differences, you are going to have to get a chiller and I personally would not have MH that close to the water besides heat issues you'll have better light dispersion higher up. Maybe try some sort of DIY hanging kit. The rest of what you have said is good, acclimate your corals and gradually bring them towards the light along with your shortened photo period.

Sregnar35
02/27/2008, 07:22 PM
I can live with my tank going up in temp a bit. It currently raises about 1 degree with the 260pc's . If the halides raise it another 2 or 2.5 I'm still comfortable with that. I could also turn my heater off during the day and set it to a timer for night periods.

photobret
02/28/2008, 12:30 AM
Those lights are going to raise hell, MH are so hot, My temp on my 30 gal running one 150w 12" from the water would go up to 86 + from the set 78. Much to say I got a chiller pretty quick! At the very least buy some cooling fans off ebay, get the 6 fan set and go from there. I am using 4 fans blowing across my T5's to keep my tank at a stable 79-80.

Sregnar35
02/28/2008, 06:03 AM
The light strip I bought has cooling fans built onto it, but I'll probably get a fan to blow across the top of the water too.

luke33
02/28/2008, 07:56 AM
At 4" above the tank those lights are going to boil the surface so be prepared. Like mentioned above i'd suggest raising them to 8-10" above the water as well.

alpine
02/28/2008, 08:48 AM
Just for reference my old 75 had 3-250watt halides and 4-96watt pcs.All bulbs were about 6"- 8" from the water surface.The only thing I used for cooling was 4- 120mm fans in my hood that turned on with my halides and a 6" honeywell fan blowing across the surface of my sump.Never had a problem with temps.Do keep in mind that I used to evap about 4 gals of water a day.

Two fans in the canopy blew air in and the other 2 blew air out.I also never had a problem with frying my corals.I did however put all new additions on the sandbed for at least 2 weeks before moving them higher up.

HTH