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Discussion Starter #1
The packaging on most CFLs states actual and equivalent (assuming incandescent) watts. I was wondering what the real difference would be between daylight CFLs having an equivalent rating of 40 and 60 watts in a 20 gallon tall tank insofar as plants are concerned. I currently have two of the 40s over the tank and suspect I could use a touch more light. Would it be too much to bump up to the 60s ?
 

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you don't use the equivalence rates they are useless for aquariums. All you care about is the actual wattage the lights use. Two 13 watt CFL bulbs (equivalence 60watts) would be perfectly fine for a 20 tall.
 

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Old post I know, but I just thought I'd add something.

An 18" T8 tube is 15W, that's what a 20g tall usually comes with and it would be fairly low light.

I wouldn't go over a dual tube setup (so 30W) as then you're pushing the limits. So with two 13W CFLs you are probably fine. CFLs can be a little brighter, at least directly under them as all there power is a bit more focused than a tube 18" long.
 

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Discussion Starter #5
No algae so far. This tank has never even had algae on the glass. The lights are on 10 hours a day and I dose once a week with Flourish Comp. This tank never receives sunlight. The tanks that have algae get some direct sunlight. The only answer for that is to block it.
 

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Discussion Starter #7
Many trials and many errors. My worst algae tank is a 55 like yours. When the hair algae hit, I set the photo period back to 8 hours and that didn't really help. A friend said to crank the lighting up to at least 10 hours and do 2x on the Flourish Comp and use root tabs for the heavy feeders. That seemed to slow the algae; however, I also added several plants. Other than blocking the direct sunlight, I think adding many more moderate to fast growth plants will help a lot. Unfortunately, I really need to scale back on my aquarium spending for a while.
 

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Discussion Starter #9
A lot of this is still a mystery to me and seems to be contrary to logic sometimes...most times. On my next off day, I'm going to hang blinds in the windows that are letting in the sunlight. They're in my old time basement, which is why I hesitated to darken things. I'm also going to plant some extras / experiments from other tanks.
 
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