captmicha

I know lumens isn't the best way to measure by but it's what I'm going to go with for right now for CFLs. I'm going to be using them until I have the money and energy to do proper T5HO lighting and maybe a PAR meter.

Is there a chart or some kind of equation that anyone can suggest for figuring out how many lumens per gallon or depth of tank?

Thanks.

D9Vin

Lumens is a highly misleading reference, as it basically equates to how bright a bulb will look to a human. But since plants don't utilize the colors that we pick up best, it won't tell you how effective a light will be for plants. Better numbers to look at are the wattage and the color temperature, the 'k' rating.

For the color temp its generally accepted that you want something about 5500k to 10000k. If you are trying to use the screw in spiral cfl types, 6500k is the highest I have seen, and what I would go with if I were you. How big a tank are we talking about?

KIG

D9Vin, wattage is missleading also isn't it? a t12 may use 50 watts, a t8 may use 25 watts and a t5 may use 12.5 watts and a t5ho will use say 7 watts, all putting out the same light. watts is the energy used not the energy output, and that is what people are interested in is the energy output, or lumens. Not trying to start an argument just questions of my own.

TarantulaGuy

What you really want is a PAR meter. That is the most precise way (as far as I know) to check light output against other light output All others are bunk. Of everything mentioned above, I think color temp is probably the *most* misleading.

Edit: OOps, see that you already have one on your wish list

Zapins

While the methods listed are not perfect for figuring out how much light you want over your tank I think captmicha is looking for a practical answer to "how much light should I use" rather than a philisophical answer or $300 light sensing machines

wpg, while it isn't accurate with every bulb type has been used for years with fluorescent bulb types and since the manufacturers make the fluorescent bulbs with the same light out put and watt requirements people have learned which plants grow with how much wpg.

The general consensus is you want 1-2 wpg of T-12 or T-8 light for low light, 2-3 for medium and 3+ for high light. If you have power compact bulbs, or T5 HO then you want 1-2 wpg for medium light and 2-3 for high light plants.

If you have an extremely small tank (under 5g) the minimum you want is about 10 watts for low light, 30 watts of fluorescent light for medium light and 50 wpg for high light. With a large 200+ g tank you can light it using less wpg simply because of the height of the tank/surface area. This is because the rule breaks down for extremely small or large tanks.

If you are determined to use lumens for some reason then look up the lumen rating of bulbs in the wpg range I mentioned. As stated lumens are balanced to the human eye which has little to do with what wavelengths are easily available to the plant. That said, total light output is more important than specific colors in general, so the brighter the light you add (even if its not ideal wavelengths for plants) will still be used because plants have many types of accessory proteins that capture the less useful light. Over time the plants simply make more accessory proteins and can use more of the "non-ideal light."