What sort of light am I dealing with?

[SWerner13]

After reading through "updating the WPG rule," I became curious and attempted to investigate as to what I had going on. However, due to my inexperience and the fact that I don't really know what I'm looking for I can't seem to figure out if I have CF, T8, T12 or what?

This is my light:
Current USA Satellite 20" 40 Watt Power Compact Fixture-Single Strip W/Lunar Light at Big Al's Online

The bulb I have is the daylight bulb which is 10,000/6700

Those of you who know more help me out please.

 

[fort384]

You have CF. Remember the WPG rule isn't scalable... in other words, you cannot apply it universally... 4WPG over a 10G tank is not going to be the same as 4WPG over a 100G tank.

It is subjective of course, but I am assuming we are talking about your 10G tank here... I would call 40W of CF over a 10G tank medium to medium high.

FYI, the CF bulbs are the crazy curved looking ones that will have various pin sizes/shapes/forms. Yours happens to be a 2 tube configuration with I am guessing a 4 pin base.

The t-5, t-8, t-12 lights are standard cylindrical tubes, with 2 pins on each end. They are described in 1/8 of an inch increments, so a t-12 is 1.5" in diameter (12/8=1.5) and so on.

 

[SWerner13]

What is different about a 10 gallon that makes what would normally be a higher light lower? Also according to that theory then I would have what? close to 7 WPG?

 

[jrp1588]

it has something to do with smaller tanks having a larger surface area compared to their volume. A 10gal has 200 square inches of surface area for its 10 gallons of water. A 100 gal has 1080 square inches of surface area. That means proportionally, the 10 gal has almost twice the surface area of the 100gal. So really watts per square inch would be a somewhat more accurate measure of light...

 

[fort384]

ok, think about it in terms of this:

IF you were to say, have a 5 gal tank, and you put 2WPG over it, this would give you 10W. Probably not enough to grow much at all.

Now, lets say you have a 100G tank, and you put 2WPG over it. Thats 200W. Probably sufficient to grow a lot of plants.

I have roughly 3-4 WPG over my 29G tank. Medium high to high light I would say. If you wanted 4WPG over a 100G tank, thats 400W of light... probably way over kill. Now think of it even in more extremes, 4WPG over a 150G tank, etc. And on the other side... 2WPG over a 2.5 gallon tank... and so on

Most consider the "WPG rule" to be an inaccurate guide (guide, not rule..) that is most effective for tanks in the 30-50G range, and then it is still subject to other variables such as photoperiod, spectrum, type of bulb, life of bulb, etc.

 

[SWerner13]

it has something to do with smaller tanks having a larger surface area compared to their volume. A 10gal has 200 square inches of surface area for its 10 gallons of water. A 100 gal has 1080 square inches of surface area. That means proportionally, the 10 gal has almost twice the surface area of the 100gal. So really watts per square inch would be a somewhat more accurate measure of light...

Makes Sense

What about the whole I have 1.75 times because I have CF or whatever? how does that apply?

 

[fort384]

Basically, T-5HO and CF's are more efficient, so they provide more lumens per watt if I am not mistaken.

 

[jrp1588]

indeed they do. The WPG rule was developed with standard t12 bulbs and medium sized tanks if I'm not mistaken. So you're lighting it better than the WPG rule takes into account, but your tank is smaller. I imagine it balances somewhat, but I imagine it still puts you a little below WPG estimates

 

[SWerner13]

Sounds good just trying to get a more solid feel for things. I'm refurbishing a 36 or so gallon tank right now and once I understand everything via experience and the 10 gallon and then its time to go hardcore planting! Thanks for the help guys.

 

[SWerner13]

When I upgrade to my next tank I plan on buying a decent CO2 system and doing some good planning right from the beginning instead of learning as I go like right now. Any suggestions for lights? I would like to have close to high light. It is a 36" by 12" by I think 20" tall aquarium