Giant LED aquarium light and my tiny tank

[davemedinis]

This is my small saltwater tank size:
25x15x20 in inch.
I got a LED aquarium light last week and it arrived yesterday.
It is built with 72pcs 3W LEDs, input voltage 3.8,input current 700 mA.
The actual power 192W.
Based on White 12000-14000K:460nm=2:1, below is its PAR reading and lumens, covering area:

2 inch:113,300 lux. PAR value:1760 m-2s-1.
12 inch:112,300 lux,1280mmol;coverage:0.8 ?.
20 inch:78,000 lux, 728mmoll;coverage:1.12 ?.

And as my tank is only 20inch deep, we measured the other data in my friends' tank.

30 inch :46,000 lux, 265mmol; coverage:1.28 ?.
40 inch: 18,900 lux,206mmol; coverage: 1.76 ?.
60 inch: 14,400 lux,138mmol; coverage: 2.269 ?.

But now it seems this 192W powerful LED aquarium light is too strong for my little tank, I am going to get another lower power LED, probably 24pcs blue 460nm and 24pcs White 14000K,total power 130W is enough.
Since my tank is only 30gallon, should I based on the 3W/gallon criterion and choose a 90W LED light for it?
Now here is the picture, does anyone can offer some advice, thank you~ :tongue:

 

[reefs4life]

You could just keep that one since you already have it and just hang it higher, looks like it's really close to the surface of the water. But you definitely need to tone down the lighting, looks like most of your coral bleached out

 

[davemedinis]

Thx

You could just keep that one since you already have it and just hang it higher, looks like it's really close to the surface of the water. But you definitely need to tone down the lighting, looks like most of your coral bleached out

I tried to hang it higher, but the light was still very strong, I am going to stop running it.
:Yikes:

 

[strgazr27]

The watts per gallon rule doesn't really apply when running LEDs. That fixture could easily light a tank three times your size. You need to either raise the light or get a different fixture. This is a perfect example of why careful research is so important. Abetted rule to follow is take your tanks surface area, multiply them and take that figure and divide by 20 for a tank up to about 21" deep or divide by 15 for tanks over that. This is assuming a quality 3 watt lED is being used. This is a rough estimate as optics can effect it but is still a much better rule than the outdated watts/gallon.

Taking your tank you have 20x15 = 300/20 = 15

As you can see you could have safely and efficiently lit your tank with a nice round 16 Cree 3w LED's. You are literally roasting the coral in that tank. I'm assuming they are not dimmable either. From the looks of it that fixture should be 12-16" from the water surface. Youll have better coverage and won't burn your corals to death. What PAR meter was used for the measurements? I ask as I see your converting Lumens to PAR values. If this is the case your PAR numbers could be way off as there isn't a good conversion factor for LED's to convert Lumens to PAR.

This is a good place to start eductaing yourself on LED's.

http://www.reefsmagazine.com/forum/reefs-magazine/82622-led-primer-jake-adams.html

BTW...Welcome to MR.

 

[davemedinis]

Thx

The watts per gallon rule doesn't really apply ...


BTW...Welcome to MR.

You are right, it is not a dimmable LED light, but that guys told me they would have a dimmable one in the next month.
I will hang it higher, and look for the other better one, may be i should get a dimmable one.
And by the way, i did not change the Lumens into PAR reading,here is the PAR reading metre, but that picture was a 55x3W model, my other friend got it.

 

[ctrayer]

you could also put a piece of plastic window screen over the tank
that would cut down the light. If you want to cut even further double or
triple up the screen

 

[Aqua Pro Builder]

Watt/Gallon and LEDs/Area are both usable methods of estimate but you must know how they come about and what are their merits. Watt/gallon is more suitable for taller tanks and larger tanks for quick estimation of pre built fixture with 60 degree lens as long as the LEDs are std power LEDs that includes 1W, 2W or 3W.

LEDs/Area is more suitable for shallow tanks and DIY LEDs because you can change many aspects of the fixture to make it work, like changing lens, distribution of the leds and such to make the results follow the formula as long as your LEDs are std 3W. With more people are now interested in the Cree XML and drive it at higher wattage, the formula needs adjusting again and that means you need re learn it again. If you can keep up, you can build lights properly with almost any power LEDs but if not, your estimate could be quite off.

Assuming you like to use W/G, than 3W/1G is good for even light demanding SPS. For LPS, you can start with 1.5W/1G, so 45W is enough to sustain your LPS in a 30G

Assuming you like to use LEDs/Area and build your own, follow the formula that RC people uses in their DIY lights.

 

[andylee]

I had a 90 watt over a 30 gallon and it worked very well. Very simple, 90 1 watt LEDs, half blue, half white. No optics. That fixture looks like massive light overdose. Put some screen up before you bleach everything.

 

[davemedinis]

good idea

you could also put a piece of plastic window screen over the tank
that would cut down the light. If you want to cut even further double or
triple up the screen

Hey, yes, dear Ctrayer, that's a good idea for you at this moment.Thx.

 

[davemedinis]

Diy

Watt/Gallon and LEDs/Area are both usable

Assuming you like to use LEDs/Area and build your own, follow the formula that RC people uses in their DIY lights.

Cree chips are good,but the DIY work will be very difficult i think. Especially while soldering them onto the circuit board.

 

[strgazr27]

Watt/Gallon and LEDs/Area are both usable methods of estimate but you must know how they come about and what are their merits. Watt/gallon is more suitable for taller tanks and larger tanks for quick estimation of pre built fixture with 60 degree lens as long as the LEDs are std power LEDs that includes 1W, 2W or 3W.

LEDs/Area is more suitable for shallow tanks and DIY LEDs because you can change many aspects of the fixture to make it work, like changing lens, distribution of the leds and such to make the results follow the formula as long as your LEDs are std 3W. With more people are now interested in the Cree XML and drive it at higher wattage, the formula needs adjusting again and that means you need re learn it again. If you can keep up, you can build lights properly with almost any power LEDs but if not, your estimate could be quite off.

Assuming you like to use W/G, than 3W/1G is good for even light demanding SPS. For LPS, you can start with 1.5W/1G, so 45W is enough to sustain your LPS in a 30G

Assuming you like to use LEDs/Area and build your own, follow the formula that RC people uses in their DIY lights.

Yet we both came up with the same number Lol....

I don't see how the older Watts/Per gallon rule still applies Wingo. 100 Watts of T5 is going to produce a set par value at a certain depth. 100 watts of LED can give completely different par readings at a given depth depending on the optics used/chosen. The only way I see the rule still being "Useable" is if the person is building the unit themselves and knows what optics they will be running.

Without knowing this (Most consumer models of LED's either don't list this or confuse the consumer w bogus numbers) I think the W/Gal rule is dangerous and misleading. This tank is a perfect case in point.

JMO though....

 

[davemedinis]

Lol

Yet we both came up with the same number Lol....

I don't see how the older Watts/Per gallon rule still applies Wingo. 100 Watts of T5 is going to produce a set par value at a certain depth. 100 watts of LED can give completely different par readings at a given depth depending on the optics used/chosen. The only way I see the rule still being "Useable" is if the person is building the unit themselves and knows what optics they will be running.

Without knowing this (Most consumer models of LED's either don't list this or confuse the consumer w bogus numbers) I think the W/Gal rule is dangerous and misleading. This tank is a perfect case in point.

JMO though....

I am OUT-DATED, Lol..
Thanks for all you guys. I will learn more.:redface: