Cyano scrubber?

[tomahawkins]

Hi,

I've been having difficulty getting a scrubber to produce green hair algae. My display tank (20 gal, illuminated w/ one 5000K 1300 lumens LED, bioload about 1 cube a day) is 7 months old and has never had any green hair algae outbreaks, just diatoms and small spots of cyanobacteria (red and green-blue slime). It has seen nitrates go as high as 80 ppm without much change. In my 35 gal refugium, I setup a float-on-top upflow scrubber illuminated by 3 5000K 1300 lumens LEDs set at 18 hours on, 6 hours off. The scrubber ran for a month but only accumulated some red slime. I even brought home a bag of green hair algae to seed the scrubber screens, but the algae lost its pigment within 5 days.

Then last month, the refugium had a big cyano outbreak, which promptly dropped the nitrate levels. My refugium has now become a "cyano scrubber": Using the same lighting from the failed algae scrubber, blue-green cyano will now quickly cover the crushed coral substrate. About one a week I stir up the substrate and catch the blobs of cyano with a screen, then I turn on a power filter to decloud the tank. Nitrate levels are now undetectable in both the display and refugium.

Anyone else with similar experiences? Any thoughts as to the nitrate and phosphate conversion efficiency and other filtration properties of cyanobacteria vs. green hair algae?

-Tom

[SantaMonica]

Yes cyano absorbs nutrients, but it takes a large surface area and it detaches and floats away easily. GHA will outperform it, if done properly and give the time.

Since your display is 7 months old and was still getting diatoms (the easiest to get rid of), it probably means you had no real export and your rocks have been absorbing phosphate all this time. Thus you only measured nitrate.

The white LED's you used for the scrubber have been tried and usually don't grow at all. So what I would do is get 660nm red led's and get the scrubber growing properly. 3 X 1300 lumens sounds huge though; you only need a few 100 for a small scrubber.