[bonsai411]

I am considering a big time upgrade to my lighting system. I have a 90 gal, 48”L X 19” W X 24”H.

I am custom building a hood for this tank to include 2x250 watts MH (10,000 K), 1x110 watt VHO (true actinic blue), and 2x55 watts of PCFs (10,000k Ice White)= 720 watts (8 watts per gal).

Therefore, is the above too much light? Is there such thing as too much light? I want the flexiblity to add anything in the tank in the future (including SPS corals and clams).

Thanks!

Mike

[Ninong]

Originally Posted by bonsai411

Therefore, is the above too much light?

No.

Is there such thing as too much light?

Yes.

I want the flexiblity to add anything in the tank in the future (including SPS corals and clams).

Your proposed lighting will be more than adequate.

[Rp Marine]

how can you have too much light?

[Ninong]

Originally Posted by Rp Marine

how can you have too much light?

Any light exceeding the zooxanthella's saturation point is too much light. If it greatly exceeds the saturation point it can result in photoinhibition. Dynamic photoinhibition causes reversible photochemical reactions that divert excess light energy away from Photosystem II through thermal dissipation but chronic photoinhibition causes irreversible damage to Photosystem II where synthesis of new photosynthetic proteins must occur before normal photochemistry may resume (Brown, 1999).

Saturation points for most corals are reached at 20-30% PARS (photosynthetically active radiation at the surface), some as low as 10% PARS and a few as high as 90% PARS (Sorokin, 1995). Photosynthesis can proceed as long as a coral's compensation point is exceeded. It isn't necessary to actually reach it's saturation point and anything above its saturation point provides no additional photosynthesis whatsoever. Greatly exceeding its saturation point can result in photosynthesis shutting down -- photoinhibition. Corals found in shallow water habitats have adapted to extreme light conditions but even they can be damaged by excessive exposure that can happen when the sea level drops drastically such as during an El Nino year.

The problem for aquarists is that not all of the corals we keep are found in shallow waters. Some commonly inhabit waters 10-20 meters deep. These corals would be damaged at light intensities lower than those that would damage corals found in shallow waters. If one were to locate a 2000w metal halide lamp -- or even a 1000w lamp -- too close to the surface of the aquarium there are many corals that would be unable to adapt to such intense light. A 2000w metal halide lamp produces 170,000 lumens. That greatly exceeds maximum noon sunlight in the tropics. And don't forget that the light intensity at 5 meters depth is only one-fourth that at the surface.

The original question was not whether the average hobbyist can have too much light using the usual 250w and 400w metal halide lamps, the question was whether there is such a thing as too much light. Yes, there is.

[kevinpo]

Excellent reply George! I run 2 - 400W bulbs on a 90 gal along with 2 - 110W actinics and I would say 250W bulbs are more suitable if you plan on having live rock and placing the corals on it (mine are on the sand bottom)

Regards,
Kevin

[Chris Lakies]

1000 watt Metal Halide over a 5 gallon tank TOO MUCH!

[cubalz]

Originally Posted by Chris Lakies

1000 watt Metal Halide over a 5 gallon tank TOO MUCH!

I think that they would call that a tank full of "fish soup" from all of the heat!!!!