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Re: Watt lumens?????
So just to clarify, lumens are a way to show light output of a lamp. Watts are difficult to use because they are based off the power consumption of the lamp and can be affected in several ways including, lamp efficiancy, spectral response, and light output angles. So when you base something on wattage, be sure to have an idea of those parameters. Such as, a CFL will have a lower wattage than a normal incandescent but a higher lumen output. A regular fluorescent will have a higher wattage than a CFL and similar lumens but its spread over a larger area so the total flux (lumens per area) will be decreased for the long fluorescent tubes. This same idea applies to LED's and halogen lamps. LED's introduce more complexity so unless you're thinking about those, i wont go into detail here.
Depending on what set up you currently have, you should look into what is available. If you can upgrade, then wiegh the costs and benefits of each. Such as a T8 bulb is longer and has less lumens per watt than a T5 and is also less efficiant. A T5HO (high output) has a higher lumen output than a normal T5 but cost slightly more. I've been told that you need to replace T5 and T8 lights every 6-9 months due to the degredation of the spectral response over time.. which leads to a high cost in the long run.
You'll also need to look at the Kelvin rating of the bulbs. That is, the spectral output of the lamps. Plants have been seen to have the best growth with 6500K lamps. So look for lamps with that rating. If you go too low ~2500K, then that promotes algae growth and looks dull and yellow in your tank.
So the best thing to do in this case, is to look at the lumen output of the different lamps for the wattage specified as well as the length of the lamp. the lower wattage with the higher lumens over the same area is what you want to go for in my opinion. So in that case, several (3-5) 26 watt CFL's over the length of your tank should do the trick and they last longer than the T5/8 lamps. You just have to find the fixtures to do so, which you can make or get wall affixed hanging fixtures with the screw in CFL's. Mixing the 6500k and the 50/50's look really cool in my tank btw ;).
Hope this helps!