how much is too much - watts per gallon?

[happygirl142]

Hi all,

I'm looking at a new light for my reef tank.
I have a 29 gallon tank. 30"long x12" x19" tall

When I google how many watts per gallon the answers vary but the average seems to be about 5 watts per gal.

Thats all well and good but when I read about what people are actually using on their tanks it seems the watts per gallon are much higher than suggested.

The light I'm looking at is a 30" light with either a 150 or 250 watt metal halide with T5 actinics and blue moonlights.

according to what I've read the 250 MH is way to much light but as I stated I see people using them so am I missing something??

Thanks

[seagirl]

depends on what you want to keep. if it is a sps tank i would get the 250. if it's a softie tank i'd get the 150. WPG is useless imo, and most people agree it is about par not watts.

[happygirl142]

Ok please ignore my ignorance on the abbreveations but what is "imo" and "par"?

[happygirl142]

oh wait imo, In my opinion, got that one!

[Badgerman]

PAR- photosynthetically active radiation. It's basically how much of the light the corals ect can use. I agree with seagirl, if you want to keep sps the best light would be the 250 watt, and as long as you hang it a good ways above your water surface, you shouldn't need a chiller. 150 watt metal halide would also work fine for sps and anything else.

[happygirl142]

Thanks for the explanation. That sounds good thank you both

[pjf]

You may need a light meter to make sure that your corals receive enough PAR (50-90 PAR?) but here’s an article that might help: http://www.advancedaquarist.com/issu...04/feature.htm

My interpretation of the article is that corals near the surface depend on morning and afternoon light for photosynthesis and shut down during mid-day when sunlight is brightest.

My recommendation is to divide your lighting into 2 halves:
• Half of your light should be ON all day (8-12 hours)
• All of your light should be ON during mid-day (4-6 hours)

The lesser morning and afternoon light benefits the corals near the top of your tank.
The full lighting benefits the corals at the bottom of your tank.

Look for a fixture with 2 power cords that you can place on 2 timers.

[wnecbubba74]

????????
Jumping in with a question????????

What would be the differents if you just left all the lights on all day?????

I have Coralife with 2x150 MH and 2x96PC....so should i run them at a different time?? I just have it all on one timer for 9 hr a day.

[skaterzero22]

i think the best situation is to come as close to the natural world as possible. when the sun comes up it isnt as bright as it is at noon. so a gradual light would be benificial to the animals, IMO.

[Ziggy953]

Hmmm...with a 29g tank I don't think I would go over the 150. That should be more then enough for anything you would want to keep in there. Add to that some actinic T5s and you should be set. If you do go with the 250 make sure to keep it off the water a good 10+ inches and have a fan on there to keep the heat down. Could get a little hot in there.

[ahullsb]

I think you would be perfectly fine with a 150 too. I have 2 150's over a 55 and I'm getting plenty of growth. The only way I would go with the 250 is if you are planning on switching to a larger tank in the near future.

[pjf]

Originally posted by wnecbubba74
????????
Jumping in with a question????????

What would be the differents if you just left all the lights on all day?????

I have Coralife with 2x150 MH and 2x96PC....so should i run them at a different time?? I just have it all on one timer for 9 hr a day.

Hard to tell without a PAR meter. In theory, if your full lighting was too bright (>260 PAR per Riddle's article) all day, you would photo-inhibit the corals at the top of your tank all day. If your MH comes on only during mid-day as in nature, then the corals at the top of your tank will be able to photosynthesize during morning and afternoon with your PC lights.

It may be revealing that many aquarists are reporting better coral growth when they replace their continuous MH fixtures with computer-controlled LED fixtures.

For my aquarium, I use 2 timers.

[happygirl142]

Pjf,
Thanks for the link. I'm going to read the article after my morning coffee so I can actualy retain it. Looks really informative.

Also I am intriged about the LED comment. Looks like I'll be reading up on that as well.

I currently have a pc light with moonlights and i use a timer to try and simulate the dawn/dusk effect. I usually have my actinics come on in the morning. Then the day lights late morning. In the evening I have the daylights go off 1st than about an hour later the actinics go off leaving just the moonlights which are on all the time.

[pjf]

You are doing the right thing with your 2 timers. The timers are a lot cheaper than $2,000 computer controlled lighting:
• Sfiligoi Advanced Control Lighting System (www.aquariumobsessed.com) for MH
• Aquaillumination (www.advancedaquarist.com/2007/10/review/view) for LED