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View Full Version : Displays with lots of Hair Algae



SantaMonica
04-06-2009, 10:01 AM
Update: Displays with lots of Hair Algae

It's happened several times now: Someone wants to add a scrubber to their system because they have a display with very thick hair algae on the rocks. They already measure zero nitrate and phosphate, and when they add their scrubber, the scrubber has a very slow start and does not seem to grow much.

Of course what is happening is that the hair algae in the display is ALREADY a scrubber, attached to the rocks! It has had plenty of time (months? years?) to establish itself, and most important, it has a gigantic area to attach itself to. So how do you beat it with your newly-built DIY scrubber? You do it with the power of light.

All algae operate on the of photosynthesis of light. The stronger the light, the more the algae will pull nitrate and phosphate out of the water, and it will pull it away from any other algae that has less light. This is important to understand: If two areas of a tank are identical, except one has stronger light than the other, the area with the stronger light will grow more algae, and, the area with less light will grow less (or none at all). This is why the top of your rocks grow more algae (it has more light) than the sides do (has less light).

So if you already have lots of hair algae in your display, you have to build your scrubber with even more powerful lighting than you normally would, so that the photosynthesis in your scrubber will overpower the photosynthesis of the algae in your display (then, after all the algae is gone in your display, you can reduce the wattage if you want). The bulb wattage to do this is about one CFL watt for every square inch (6.25 square cm) of screen area. Example:

Say your screen size is 10" X 10" = 100 square inches; if you did NOT already have a lot of algae in your display, a 23W CFL floodlight on each side of this size screen would be sufficient to keep all nuisance algae away. This would be 2 X 23W = 46 total CFL watts, for 100 square inches of screen. This is about a half watt per square inch. But to beat a large amount of established hair algae in the display, go for maximum power: 1 watt per square inch. This is about twice as much. So, using two of these same bulbs on each side (4 total bulbs) would give you about 92 total watts for 100 square inches, or, almost 1 watt per square inch. This would do it!

Note about wattage: We are talking here about real CFL watts, not "equivalent" watts. If the bulb says "23W = 120W", or "23W equivalent to 120W", we are talking about the 23. And if you are using T5HO, such as a 24 inch 24W bulb, you just use the wattage it says.

Another trick: Add a lawnmower blenny to the display. He will eat the "scrubber" in the display, so that the scrubber you build gets off to a faster start.