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So I'm better off getting 2 2X39W fixtures then?
One option would be to go with two separate fixtures but I agree with maknwar - 2x39 on your tank is sufficient. I think what was suggested is that another option would be to go with a single fixture with two separately wired switches allowing you to turn on two bulbs at one time, or all four bulbs at a time. I think ... someone refresh my memory ... is it Catalina that has some nicely priced fixtures that have the multiple switches? Well, let me rephrase that - many fixture manufacturers have that option (I just sold my Tek that had that option), it just depends how much you want to spend. But I thought at one time Catalina had a 3 bulb fixture that would fit a 40-breeder, allowing you to power on two bulbs, and power on the third if you wanted a mid-day "burst". And that, IMO, would be ideal. I think you'd only use two bulbs, but you'd have that flexibility if you needed the third.

Honestly, for the plant list you posted (which don't need to have high light blasting at them) you could probably deal just with the 2-bulb fixture and save yourself some cost. In my opinion, 4x39 watts may be a bit too much and invite algae unless you achieve the tank parameter nirvana with your CO2 and ferts and such.

Just my opinion and I'm not an expert - just going based on what others advised me at one time and what I experienced using 2 vs 4 bulbs on my 50-gallon pressurized setup (which had same footprint as 40-breeder, just slightly taller I believe).
 

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So I'm better off getting 2 2X39W fixtures then?
He was suggesting that you get a 4 bulb fixture and run the outside lights. I read something about the break in between the running bulbs impacting light intensity, but I am definitely not sure about that.

In my own tank, I have a 3 bulb fixture and only run the outside 2. Some of my plants get a bit leggy, which leads me to believe that the light intensity is not as strong as I had hoped. On the other hand, I have algae despite showering the tank with CO2 and ferts daily. One day I'll figure it out (I hope).

People have some amazing looking 40b with a normal 36" double bulb T5HO fixture. Seems like the type of reflector the GLO fixture has might be well suited to reach the front and back of the wide tank. Once again, I would check with others on that.
 

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I have a 4x39 fixture on a tank about the same size as yours and 2x39 is perfectly fine. I have mine set up to run the inner bank half of the photo period and the outer bank the second half. I could have gotten away with just a 2x39. I also adjust the height of the fixture so play with intensity.
 

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i run 2x39x on mine as well. tried 3 (2 fixtures on the tank with one disabled on the second one and got nothing but algae. this was with high co2, ferts, and limited light (8 hours/day or less). turned the second one off algae disapeared. bottom plants dont grow as well though, but i think it has more to do with the fact that the 2 bulbs (CA fixture) are centered in the tank (4" above) and the 40B is a wide one.
 

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It really depends on the fixture/bulb combo. Not all fixtures are created equal. If you're looking into a 2 bulb fixture, like Hyzer already pointed out I'd go with the GLO 2x36W fixture. It has a very nice single parabolic high quality reflector that is very efficient with spreading the light from the 2 bulbs. Otherwise, if it aint a TEK fixture, most likely the reflectors are meh.
 

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I just purchased a 40b and am planning on using the 4x24w t5ho fixture that I had on my 37g. The 40b is wider and longer but is more shallow so if I raise the fixture above the 40b (instead of having it on legs like I did with my 37g) it should be fine.

That being said, I think a 2-3x39w will work well as long as you can raise it over the tank to get a good spread.
 

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IMO, your heading for an algae farm using that much light over a 40g breeder. 2 T5HO bulbs is plenty of light.

Catalinaaquarium.com will customize any fixture to suit your needs. They are reasonably priced, great customer service, I own 4 of their fixtures. I hear there ballasts are good, but their reflectors are not the greatest. Even so, I am very satisfied with them.
 
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