Reef Tank lights

[dalerich]

I'm looking for a formula that will help me calculate the lighting requirements of my fish tank.
I have a 55 gallon tank. The lights sit 24" from the bottom of the tank. Does anyone know a formula to calculate the proper lighting requirements to meet the descriptions below:
Low light
Medium light
Moderate light
Strong light
Very strong light
The Saltwater 101 lighting on the New Hobbyist page said:
Watts: The amount of electricity used to power the bulb. It is NOT - I repeat NOT - the output of the bulb. There is a direct relationship between power consumption and output, but Watts are NOT a measure of output. They measure input. This is one of the reasons why WATTS PER GALLON IS A USELESS RULE! Do not use it! (I'll expand on this in a minute)In addition to the notion that watts measure input, not output, another thing to consider is that as a tank gets deeper, the less light is penetrating the water. For example, if you have a 20 gallon tank that is 5 inches tall (its an example, not reality), and run 100 watts of NO fluorescent lights, thats about 5 watts per gallon. But what if the tank was still a 20 gallon tank and 100 inches tall . . . do you think that its going to be just as bright on the bottom as the 5" deep tank? I hope not . . .
I understand why I should not use this watts per gallon rule but what can I use in place of it?
Maybe we need to pool everyone's tank and make up a rule the first one to make up the rule gets to name it after themselves...

 

[6stokes]

Well the quote is right, but he's a little carried away. If you have a standard sized tank (not too tall) then the watts per gallon rule of thumb is pretty good. In order to do it correctly, you would need a meter than measures lux, I think it's lux, if not lux, it's some measurement of light. I think these meters are pretty expensive to use under water. And you would only need it once or twice.

 

[bang guy]

Originally posted by dalerich
Does anyone know a formula to calculate the proper lighting requirements to meet the descriptions below:
Low light
Medium light
Moderate light
Strong light
Very strong light

Those are all subjective values. Personally, I like the Watt per gallon guideline for new hobbiests. It's easy to understand.

 

[dalerich]

okay the watt rule is for standard tanks then how many watts equal the following:
Low light
Medium light
Moderate light
Strong light
Very strong light
I realize that watts works well with a standard light bulb and watts = power and power = current X voltage.
On a NO,HO or VHO or MH does watts rule still work?
I have a 15Watt NO fluorescent bulb is my calculation for this bulb 15 or does it matter if it's 6000K or 10000K or 20000K.
Nothing to do with a reef tank (my compact fluorescent bulb that screws into the lamp in my living room says in the instructions that 1 Watt of Fluorescent Light equals approximately 5 Watts of Incandescent Light.)
Does that mean that 15 watts of fluorescent equals 75 watts in my watts per gallon calculations?
Sorry to everyone I'm an application engineer with a salt water tank.
Thanks for the reply 6strokes I'm just trying to understand all of this and i'm not trying to be smart ass.

 

[6stokes]

Understand, we are all here to learn and I didn't take it any other way. Bang or someone will have to help you on the different types of bulb output and what would fit under your pre-defined categories.
Just so we are all on the same page: Watts= power consumed and volts times amps will give you the watts consumed in an hour if my memeory serves me. The Kelvin ratings on the bulbs determine how much blue in the spectrum is provided and is usually a personal preference, however, the blue rays do travel further.
1 watt equaling 5 watts: I believe the watts per gallon principal is based on florencents, but your question about VHO vs HO is a good one.
Sorry I'm not a lot of help in this area.

 

[thedude]

About the watts per gallon "rule", I think he was trying to say that its more of a "guideline" than an absolute rule. But, since the guideline is pretty vague (5-10 watts per gallon), and most people have pretty similarly shaped tanks, I dont think you could really go wrong as long as you err on the high side.
Using this basic guideline only, I would answer your question with these values, remember...these are overly-simplified answers to an overly-simplified question, I dont want to get flamed for giving such an exact "recipe" to such a delicate technique:
Low light...... (2 w/g ) 110watts
Medium light...... (3.5 w/g) 192.5 w
Moderate light ...... (5 w/g) 275 w
Strong light ..... (7 w/g) 385 w
Very strong light..... (10 w/g) 550 w
As for potential combinations of MH and VHO, amounts and ratios of mixed actinics, and K levels, I would like to know too :happyfish

 

[bang guy]

My subjectivie opinion is similar to TheDude.
Low light: <4wpg
Medium: 4 - 6
Moderate: 4 - 6
Strong: 7 - 9
Very Strong: 10
Intense: 11+
Kelvin Color makes no difference except for the asthetic look IMO.
As far as "my compact fluorescent bulb that screws into the lamp in my living room says in the instructions that 1 Watt of Fluorescent Light equals approximately 5 Watts of Incandescent Light." Incandescent lightining is so inefficient as to be completely out of scope for reef lighting. The WPG guideline is only applicable for high efficient lighting. It's also just a Guide ie. starting point.

 

[golfish]

Lots of things to consider when talking about lighting...When we talk WPG its assumed that light is evenly spread though out the tank..But, 400 watts of NO lighting wouldn't compare to 400 watt's of VHO and the 400 watt's of VHO doesn't compare to 400 watt's of MH.
It really depends on the corals..Some corals do better then others under VHO's..Some do better then others under MH's
If you go back you'll see dalerich is looking for lighting for his "fish tank"....There is no "guideline" for a fish tank that I know of

 

[bang guy]

Hey man, this is a Reef Forum, No fish allowed!

 

[daceman89]

so how much light is recommended for a sps reef tank like a tank fmainly acros. if anyone can do the math i have a 180gal. i would assume that the eqausion would be # of watts per gallon times amount of water per gallon.

 

[bang guy]

Acro = Very Strong or Intense lighting IMO.
This animal is also for the experienced reefkeeper who already has the knowledge to know what lighting is required.

 

[dalerich]

Sorry to all for the reference to a fish tank.
The tank is going to be a reef tank once I get the correct lighting. Thanks to all for your help.
I either need 5.7 four foot FL lights or explore the MH lights. Still have to figure it out before buying any expensive corals.
Thanks again and sorry for the fish tank insult.

 

[bang guy]

When looking into lighting be sure to look into long term costs. Not just the up front purchase price.