Watts per Gallon

[gooyferret]

Just a little poll to see if people believe if watts per gallon should be used for the amount of lighting needed for an aquarium.

Leave a thread stating why you polled the way you did, and how you feel about the watts per gallon ratio.

 

[fishfreek]

I voted partially accurate and this is why.

If your going to light your tank with florecents then yes it will give you a 'target' to aim for. If your going to use MH then no the rule of thumb is useless since a MH bulb does not and will not light the entire tank with the same intensity as a long florecent bulb.

As a general rule a MH bulb will light with a good overall intensity a 2' square area. If your tank is only 2' long or less then 1 bulb and the watt per gal rule might hold some weight. If your tank is 4' long and you put a MH bulb over the middle then you will have a very bright middle of the tank (minus the shadow from the center brace) and somewhat shaded ends of the tank. TO evently light a 4' long tank you need two mH bulbs. Since the bulb on the left does very little for the stuff on the right side of the tank its not proper to use its wattage in the calculation for corals on the right side of the tank.

Here is an example

4' long tank with 4 X 2' long 55W PowerCompact bulbs will evently light and provide 220W of light.

The same tank with 1 175W MH placed in the center will provide 45W less of light (using just raw wattage ratings. In honesty the MH bulb is more INTENSE than the PC's) but since the bulb is in the center you really oly have the light over the middle of the tank.

Take two 175W MH bulbs and put them 1' in on each end so that they evently light the entire tank. Now you have 350W of light over the tank but if you only power up 1 bulb you will notice that side gets 80% of the light whle the other side is hardly lit up at all. Thus the 350W of light is not evenly distributed over the tank its more like having two zones at 175W.

Now. Im not saying either type is better than the other but of the above examples they both have their useage and place depending on what you want to keep.

 

[Guest]

I voted partially accurate also..

Just as Aaron said, the PC, and flourescents can benefit by watts per gallon where HID MH lighting cannot be measured by watts per gallon, but rather foot coverage. rated by cubic feet

 

[astride13]

I went with Not Accurate. Although it is a good guide line for quick measuring, it does not take into account the depth of the tank. A 20 long and a 20 tall should not have the same lighting to get equal coverage.

Here is my new method that I have just invented. I played with some numbers and it seems a bit more accurate. The 66 is the static number that we can play with. It would need one for Corals and one for Fish only.

Watts = (SurfaceArea / 66) * Depth

55 Gallon = ((48 * 13) / 66) * 18) = 170 Watts
10 Gallon = ((20 * 12) / 66) * 12) = 43 Watts

There are also other considerations like fishfreak and timbo2 said.

What do you guys think? Are we on to something or is the older method just easier?

 

[gooyferret]

astride13, I agree with you and this is the purpose of this post. depth of a tank is very important concerning lighting. What really bothers me JMHO is that people ask constantly what kind of lighting should i get and how "strong". MOST people will reply oh i would recommend about 4 watts per gallon well you get the idea. Since i have been into the hobby i have been researching lighting constantly because i feel its #1 essential with the enviroment in which your fish and corals live.

Here is my new method that I have just invented. I played with some numbers and it seems a bit more accurate. The 66 is the static number that we can play with. It would need one for Corals and one for Fish only.

Well astride im agreeing with the first part but wheres the 66 come from? Also in a 55 gallon wouldnt it need more lighting in ratio to a 10gal? (considering you use the same type lighting for both)
I feel that watts is totally irrelevant for aquarium lighting. My biggest reason is because of watts is TOTALLY not in relation to light. Light is measured in lumens wattage is merely what the bulb is burning for electricity. Kelvins is also another factor in proper lighting. Another fact to consider is surface tension. Having surface tension will improve penetration of lighting through the surface of the water. Well thats enough for me ill let someone else talk

 

[gooyferret]

Double post: Edited 10:56 PST 08/15/03 steve-s

 

[ConanTheLibraia]

I believe it gives you a good general idea of the strength of your lighting vs. the rest of your tank set up.

 

[Zack]

I feel that it is totally wrong for the reasons fishfreek gave

 

[steve-s]

I feel that it is totally wrong for the reasons fishfreek gave

All are entitled to express their views but do you have anything to add that backs up why you say that

Cheers
Steve

 

[kidafius]

I voted partially. I agree with the 2' halide comment. I also agree with the depth aguement. Here's my take. If you have 4 watts/gallon on PC, I think you are doing good in a <24" tall tank. I wouldn't suggest anenomes, but you could pull some sps.

Hallides are reputed to be specific bulb wattage for depth. Something like 175 W for 18" and less, and 250 for 24" and less depth.......I'm not exactly sure. So, you can't really count the wattage/gallon. You can't use it because it is a double standard. Wattage/gallon is/should be a general PC lighting guide, and only if its understood that you use the appropriate lumen light, aka 6700-10000k bulbs and/or actinins. Halides, measured in depth. JMHO, though.

 

[Zack]

Steve,
When i first started it out and believed my fish store i have like 4 50 watt NO bulbs over my tank for 4 watts per gallon, my bubble coral did not do to well untill i got my 150 att MH, which is 3 watts per gallon

 

[mojoreef]

Ok Stevie I'll bite . I really think WPG is a useless way to get a grasp on your tank linghting. Thier are way to many varibles that come into play. Examples of the extremes would be the following. A person has a 4 foot tank with only 1 Mh bulb. So say it a 90 now they are only going to get a 2 sq.ft of good lighting the rest will suck. Say a person has VHO or PC lighting. Well 200 watts of VHo is spread over the length of the 4 foot bulb where on 200 watts of MH its spread over an inch. More point of source, better setup. Say I have 4 250 HQI MH over a 8 foot tank About 500gals) that would only be 2 WPG, but in reality thats an awesome lighting setup???

Thier are just to many variables, and it tends to leed folks astray of what they actually need. Anyway just my 2 cents


Mike

 

[steve-s]

Agreed there are many variables to consider and the WPG guideline should only be used as a rough estimate or possibley not at all. I was not really arguing that point at all.

Disagreeing is perfectly acceptable, especially in this hobby I was more curious as to people's reasoning. Simpley stating an objection without the reasoning behind it doesn't help further the discussion.

Cheers
Steve

 

[mojoreef]

Agreed, Alot of times folks make these little formulas to help out and then after a year or so they turn into the grand fubaaa


Mike

 

[gooyferret]

mojo and steve,
Ah yes your so correct! Lighting has far to many variables to be in any way accurate and this is why i posted this poll. Watts/gallon is totally irrelevant. It was also stated that MH are based off wattage for depth. I also find that incorrect. IMHO i feel that watts per gallon is totally inaccurate for any measurement of light. Considering watts is based off of electricity consumed not light produced, im working on a way to calculate watts per gallon to lumens per gallon. Lumens being since thats how light is measured.

 

[Guest]

You guys might want to check this out!


http://www.thekrib.com/Plants/Tech/intensorama.html

http://www.thekrib.com/Lights/depth.html