Can you have too much light?

[fishdude]

:idea: I have access to a 3 x 250w double ended Metal Halide light but I only have a 4 x 2 x 2 foot tank would this be too much for my tank or would the fish/corals etc. that I plan to get actually be better off? I would like to be able to have a wide variety of corals, also the 2 x 250w MH are dearer than than what the above light is which is why I am asking. If someone could enlighten me that would be fantastic - Thanks

 

[mojoreef]

You can have to much light. But the 3 x 250 watts will be ok. You can do things like hang them a little higher and reduce the photo period to adjust to the type of corals your going to keep.

Mike

 

[reedman]

It really depends on how your rock work is set up and what corals you keep. Trying to keep a variety of SPS under that lighting will work out great. Keeping a variety of soft corals, might prove to be a challenge (possibly too much light). The key is to establish some overhangs that will provide shaded areas for the lower light animals while still allowing area for the light loving specimens. 3 250s over a 4 x 2 area is a bit more than is necessary in my opinion, but I doubt it would be detrimental to the animals. Acclimation is the key. Most animals will adapt if given the oportunity without shocking them. Transition any aquisition from the existing lighting to your lighting gradually and you should be fine with either scheme you are describing.

 

[cheeks69]

Since each MH bulb covers 2'x2' section 3 bulbs would be unnecessary and would just increase the heat and the electic bill IMHO

 

[wrightme43]

Well if it cost less for 3 than 2 you can always just not use one of them. I dont believe it will really cause a problem if you do like mojo said and just keep them up a little higher. Though if it were mine I would just use two. Maybe sell the other socket and refelctor and ballast if it is seperate for some very nice bulbs. Or keep it and use it later for another tank. Steve

 

[M.Maddox]

If you haven't made your purchase yet, I would use 150 DE units instead, or 175 SE's. 250 is just excessive for a tank only 2 feet deep. Why increase the bulb distance, when you can get lower wattage, consume less resources, and spend less on electricity?

 

[mojoreef]

Well having three opposed to 2 would allow you to blend lighting, and really it depends on the actually bulb your using for the tank. You could have 3 bulbs of one type putting out far less then 2 of another type??


Mike

 

[bradreef]

listen to mojo. use 3 and go 10k 20k 10k or the opposite. corals will love it. just aclimate your coral to the light. Start them off low and then raise them up.

 

[Llarian]

250W is excessive for a 2' deep tank? Man, that runs completely counter to pretty much everything I've been reading. heh

Mojo, you mentioned hanging the lights higher off the water. Correct me if I'm wrong, but doesn't that make very little difference in the long run? Light transmits through air extremely well and I can't imagine another 6" or so makes much difference in terms of light transmitted into the tank. Now if you're adding another 6" of water it would clearly be another story, but I'm not sold on the extra height thing. Enlighten me? =)

-Dylan

 

[clayswim]

Light doesn't travel well through air either, just better than it does water. You'd be surprised how much light you'll lose in 6", especially if you're losing light away from a reflector. As for 250W lights being too much for a 24" tank, I don't see that being a problem. In fact a lot 24" SPS tanks have 400W lights hanging over them with fantastic results. In my personal opinion you begin to lose too much light in a 24" tank with 175W bulbs, at least for light-loving creatures like SPS and clams. Remember that whatever we place over the tanks, we'll never match full-sunlight. Only the normally-shaded animals will suffer.

Clayton

 

[mojoreef]

Hi Clayton good post. Another thing that comes into play is the reflection angle into the water.


Mike

 

[clayswim]

Thanks mojo. Your comment on the angle reminds me of something else, surface agitation. This is something that's not often discussed, but can affect how much light reaches the depth of the aquarium. Water with a lot of turbulence, like reefs, normally have a great deal of agitation on the surface, which light can reflect off of. Light that hits still water, like a slow-moving freshwater planted tank, will have a small amount of reflection and refraction; but as you add agitation you also add different angles to the water's surface. When the light hits those angles it can bounce off and end up who knows where. Although not studied much to my knowledge, it's been a theory for a long time that fast-moving current requires more light than slow-moving current.

One more note about light and air... I had an Iguana for years, and it's extremely important for them to get enough UVB rays for proper bone growth. Being in the always sunny (not really) Pacific Northwest we don't always have good access to direct sunlight, since glass and especially acrylic block UV rays. That meant relying on artificial light. Under normal fluorescent tubes the amount of UVB at 6" was pretty decent, and was enough for reptiles to use. If you raised the light 12" though it provided almost nothing for UVB. Being on the extreme "blue" end of the spectrum UV rays are filtered out fast, but it happens eventually to all light.

Clayton

 

[BCT182]

listen to mojo. use 3 and go 10k 20k 10k or the opposite. corals will love it.

Mmmmmm...... Perfect blend

 

[M.Maddox]

Light doesn't travel well through air either, just better than it does water. You'd be surprised how much light you'll lose in 6", especially if you're losing light away from a reflector. As for 250W lights being too much for a 24" tank, I don't see that being a problem. In fact a lot 24" SPS tanks have 400W lights hanging over them with fantastic results. In my personal opinion you begin to lose too much light in a 24" tank with 175W bulbs, at least for light-loving creatures like SPS and clams. Remember that whatever we place over the tanks, we'll never match full-sunlight. Only the normally-shaded animals will suffer.

Clayton

I've kept shallow water SPS under a 150 SE @ 20" no problems, with great growth. My point is, 250w is just unecessary unless you want the most demanding species on the bottom of your aquarium.

I agree that we'll never match the quality of NSL, but we can definitely exceed it's intensity in a closed environment.

 

[fishdude]

Thankyou everyone for all of your comments I have got some really good info. from this

 

[bswim]

Thanks mojo. Your comment on the angle reminds me of something else, surface agitation. This is something that's not often discussed, but can affect how .................................
Clayton

Gotta watch these swim guys though