05-25-2013, 10:05 AM
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I would get different tubes. What you are proposing will not likely help. I have experimented with these myself, so allow me to explain.
Tubes come in standard sizes (lengths), and basic wattage for the length. But the actual intensity of light emitted from a tube depends upon the phosphors and tube construction, and this is where they differ substantially.
The less expensive tubes by GE, Phillips and Sylvania in the 4-foot length are quite good; I use these on my dual-tube 4 and 5-foot tanks. But the smaller sizes like the 24-inch are not worth getting at all. I did an experiment over several months on my 29g which has a single T8 24-inch tube over it. The existing Life-Glo tube weakened due to age (I had it on for over 18 months) and I noticed this by the plants. So I replaced it with a GE Daylight 6500K. Within a matter of weeks, all the plants began dying. I left this tube in for 4 months, and basically killed everything except the Java Fern. I left the plant roots [some had like a single leaf yellowing, nothing more] and put a new Life-Glo tube over the tank. Within 3 weeks, leaves began appearing on the crypts, then the pygmy chain swords began rebounding though some didn't, being too far gone. The intensity of the Life-Glo is considerably more than that of basic tubes, at least in these smaller lengths. I've no numbers, but the proof is in the pudding, as they say.
So, to your Brush Algae. Normally this will occur on plant leaves due to too much light, or too many nutrients when some other nutrient is insufficient to balance. I have had both situations. So the trick is to find the balance. Brush algae on wood or rock is fine, I leave it alone. I take steps to correct the balance when I see it increasing on plant leaves.
First step here is to improve your light. As you intend staying with the present fixture, which is low light no matter what tubes, I would suggest you get Life-Glo tubes or ZooMed's UltraSun. The Life-Glo is what I use on all my single-tube tanks. They last for 12-18 months. They are more expensive, but they are superior as I mentioned above.
Second, use a comprehensive liquid fertilizer like Flourish Comprehensive Supplement once a week; in a 55g I would dose 1 teaspoon on the day following the water change every week.
Third, keep direct sun off the tank. Sun light is very bright, even more than we realize, and just an hour of it makes a big difference. Algae is able to take advantage of imbalanced tanks, where light and nutrients are not properly balanced, and the plants cannot adequately compete in this situation.
Hope this helps to explain things.