Halide Penetration

Is it true that the higher end of the halide kelvin rating penetrates less deeper then the lower end & that their a cooler bulb, like 20k and more so 30k penetrate less deeper then a 14k bulb?

 

i am unsure to the actual answer but i would assume the opposite is true.
since the deeper in the ocean the bluer the light. so it would stand to reason that blue penetrates better.

but i do know that blue bulbs put out less par then redder bulbs

 

If your talking about PAR levels deeper. The Kelvin does not have any bearing on PAR levels at depth. It used to be that the higher the K the lower the PAR. But that is no longer true.

J

 

ok, i think i got the par side of it now, i changed my 14k to 20k to see if i like them better, they are ok, but the light does not seem as bright in places, is it ok to lower my halides now i have 20k or would they still have the same effect as the 14k

 

Check Out Sanjay's Lighting Guide

Manhattan Reefs - Sanjay's Lighting Guide

 

You have a very good question. The answer is it depends. It is true that the blue light will make it through more water before being attenuated by the water, but in the normal depths of our tanks it is not relevant.

Now most higher K bulbs put out less PAR than lower K bulbs, so in general you get less light in the bottom of the tank with a higher K bulb than a lower K bulb, but this is not a hard fast rule since some 20,000K bulbs put out more total light than a 10,000K bulb. So you have to look at the actual light in question, not just the wattage/color temp.

As well the reflector will make a big difference, if you change from a high par bulb with a poor reflector setup, to a lower par bulb but a better reflector, you could end up with quite a bit more light into the bottom of the tank.

Kim

 

Thanks so far, just a bit concerned because now i'm using 20k bulbs the tank looks much darker, and miserable like a rainy day, might swap back to my 14k, this is a link to the 20k bulbs i bought,?

20k 150W Metal Halide Bulb Lamp Marine/Reef Aquarium on eBay, also Lighting, Fish, Pet Supplies, Home Garden (end time 19-Mar-09 07:21:59 GMT)

 

There is a very good chance that you have a lot less usable light now than you did with the 14k bulb, but without a PAR meter it is hard to say. I do not think there are any published tests of that bulb so you can not do a comparison to other bulbs.

So you went up to a 20K bulb, which is normally less light, and you went to a no-name bulb, which could also be a very low light bulb, so you might be quite a bit less light. But without measurements there is no way of knowing.

Now the tank will look much dimmer to the human eye with a 20k bulb verse a lower K bulb. The human eye is very responsive to green/yellow light, and much less responsive to red and blue lights. You newer bulb should have a lot more blue in it, so even if there is the same amount of energy, it will look much dimmer to you eye than a bulb that has more green/yellow in it.

Kim