Too much light??

[StirCrazy]

Originally Posted by Canadian

Also note that the upper values of measured PAR in this study were around 1100 which are readily achieved in a typical aquarium with 2 x 250W MH:

where did you find this in the article?

If they were getting PAR that high from anything under a 1000w bulb, they were holding the sensor 2 to 4" from the bulb.

the highest output bulbs I have tested so far were SE AB 10K's running on a magnetic M80 ballast, at 12" of water and air (7" air and 5" of water) they were putting out just shy of 700, at a depth of 23" water and 7" of air they were putting out about 480 to 500. I have tested 4 400 watt setups and various other 250 watt (both DE and SE) and none have come close to these numbers except the 400 watt iwasakis, which were about 20 points lower.

Bulb testing the way it is done on the bigger boards is stupid and useless to us as it reports theoretical numbers, not what you will actually get. So yes I could see theoretically the ability to supply to much light, but in reality I don't think you or me will do it. I am going to have my bulbs more than 1" above the waters surface and I am going to have my corals more than 1" under the surface. If they happen to grow to the point where these is to much light then they will simply stop rising and spread out instead. come to think of it I had a digitata do this in my old tank, grew to about 1" under the water surface then tabled out. was beautiful, but it never slowed in growth and I would be willing to be its growth could have been measured in oz/day. but at any rate I don't believe it is something we have to worry about in a practical application.

Now lets stop scarring everyone from adding to the discussion, if we want to keep going back and forth we should get a coffee

Steve

[kipsix]

Originally Posted by StirCrazy

Now lets stop scarring everyone from adding to the discussion, if we want to keep going back and forth we should get a coffee

Steve

Well, I only started this thread as I was struggling with 2, 4, 6 and 8 Bulb T5HO. Curious whether you could effectively kill your coral with too much light. Now I have heaps of reading to do.

Once I have finished reading all the links and studies.... thanks for your replies.

[StirCrazy]

Originally Posted by kipsix

Well, I only started this thread as I was struggling with 2, 4, 6 and 8 Bulb T5HO. Curious whether you could effectively kill your coral with too much light. Now I have heaps of reading to do.

Once I have finished reading all the links and studies.... thanks for your replies.

In my opinion you could never kill coral from T5's, the light we are talking about is high wattage MH in shallow systems and even then it won't kill them, but at worst from what I have taken out of the last few articles and several others I have read, is slow down there growth from an optimal rate and waist money.

Steve

[kipsix]

I kind of figured you it was unlikely to fry coral with T5's but I wasn't too sure, thought I'd throw it out to the experts and see what the ruling was.

Will it matter if the tank is only 16" deep, and I cram 8 bulbs over it though? Probably going to be mostly softies and LPS.

[Canadian]

You could certainly get some bleaching of even Acropora sp. at 16" depth with 8 HO T5s - especially if not acclimated properly. And especially if a quality fixture with active cooling is used.


Steve,

That quote you were asking about isn't from the article. The PAR of 1100 is from the article but the portion about 2 x 250W MH producing this comes from Apogee measured values from a hobbyist's tank. While 1 250W MH produces the values you've reported the cumulative effect where they overlap with 2 x 250W MH could certainly produce that level of PAR at several spots in the tank - especially with a high quality reflector. For comparison see the picture below where 6 x 39W HO T5s in a crappy Tek light produced the PAR levels seen in the picture:

http://i85.photobucket.com/albums/k72/jartanyon/par.jpg

Fijiblue, the same hobbyist who was running the T5s in the picture above decided to try MH again with 2 x 250W MH over that same tank and found he was getting over 1100 PAR at the surface.

[StirCrazy]

Ok, I agree with that kinda of output in the air at a couple inches. When I did my testing on my tank I did that then I started at 6 or 7" below the surface where it had dropped off from around 1100 to about 700, so it does attenuate quite a bit when you bring water and depth into play.

yes, VHO, PC, even NO will bleach a coral if it is not acclimated properly, I am assuming that the acclimation is proper and we are not dealing with that.

Steve