Lighting question... (watts per gallon)

[badazztealcobra]

I always hear people talking about watts per gallon in their tanks, and was just curious how you get that number.... Like my tank is sold as a Biocube 29 which is supposed to be "29" gallons.... But if you take into account that the back three sections of the tank are used for filtration, it actually holds around 26 gallons of water. With the LS and LR in there, Im actually closer to 22 or 23 gallons of actual water. So when I try to figure out my "watts per gallon" do I go with the 29 or do I go with the actual amount of water that is in my tank ?!?!?

 

[MrMexReefer]

from what i heard, its more about quality of light than quantity. I kept a lot of stuff (softies) successfully under low watt T5's in my nano tank. But yea... its good to get an idea with the "watts per gallon" system.. but its not fool proof. Just my two cents

 

[badazztealcobra]

Oh, I know its not the ideal way to figure it out, just curious how to get the "magic number" :lol:

 

[desjardiniidj]

I think it's supposed to be off of the overall tank size(29). Just to get an idea of how much light you have. I think it can be a misused formula though. Someone could say you need 10watts per gallon for sps. You could load a tank up w/ 40 watt bulbs to get to the 10 wpg, but that doesn't mean you can grow acro in it. Its really up to what you wanna do. The lights in there should do you good for most corals aside from sps and clams. JMO

 

[rickyb]

A well debated topic.
I stopped using watts/gallon long ago. It all depends on what lifestock you want to keep and the depth of the tank. These are the first things that come to mind and I'm sure there's more.

 

[squibley2]

The always over stated wpg is simply a yardstick something to get you in the ballpark. But that is one small piece of the puzzle. I have had a 20G tank with 130W of PCs over it and 20G tank with 150W MHs over it. The difference in 1 wpg in this formula would tell you that the difference was minimal but if you saw the difference it would be very obvious that 1 wpg was not the difference. The biggest thing to look at is what you are planning/trying to keep and how deep the water column is. The deeper the column the stronger the light has to be to penetrate. So I guess what I am trying to say is don't worry about your watts per gallon. I have had people tell me I am crazy for putting 15 wpg over a tank but as long as heat is not a problem and you have everything else in order I have never had a problem with large amounts of light over a tank. I have even put a 250W MH over a 20G tank.

But to answer your original question I have always been told you use the effective amount of water that is in the tank, not the stated size of the tank.

 

[badazztealcobra]

<a href=showthread.php?s=&postid=8790084#post8790084 target=_blank>Originally posted</a> by squibley2


But to answer your original question I have always been told you use the effective amount of water that is in the tank, not the stated size of the tank.

Thanks Squibley.... thats what I had been told too.... Like I know I cant have SPS under my PC bulbs, I just wanted to try to figure out what my "magic number" is..... I am going to be trying to stuff a metal halide into my tank eventually, I just wanted to figure out how everyone on here got their WPG.

 

[Rod Buehler]

Like others have said, WPG is pretty much irrelevant and IMO should never be a rule. My example: I can put a 250 watt halide over an acro that is sitting on a corner step of a swimming pool, and that acro will do well under .00000000124 WPG. VS putting a 60 watt incandescent bulb over a dixi cup which is a helluvalotta WPG, but it aint gonna grow acros.

 

[Victoly]

<a href=showthread.php?s=&postid=8791013#post8791013 target=_blank>Originally posted</a> by Rod Buehler
Like others have said, WPG is pretty much irrelevant and IMO should never be a rule. My example: I can put a 250 watt halide over an acro that is sitting on a corner step of a swimming pool, and that acro will do well under .00000000124 WPG. VS putting a 60 watt incandescent bulb over a dixi cup which is a helluvalotta WPG, but it aint gonna grow acros.

Where have I heard that before???

 

[xxpipedreamxx]

i have a 29 gallon tank with two 65 watt pc's and one 150 watt metal halide.