Green Hair Algae not growing - would appreciate help

I implemented my external ATS 4.5 weeks ago, and have yet to see green hair algae growth. In fact, besides what seems to me as some light diatom growth on mesh screen I am not getting anything.

Here are the specs. I had a 24x24x6 inch (that's 6 inches deep or 3 inches between clear face of scrubber and screen) acrylic box made so I could run the ATS external to sump. I had SM make my 22x22 screen for me - so we can rule that out as possible problem. I use a Mag12 to feed waterfall pipe so flow not an issue. I have trialed several different waterfall pipe types, particularly the slot, and have settled on approx 3/16 inch slot with no cross cuts and I have a very even (and fast) flow. I am running this 1 sided for now - mounted to wall (if necessary, I can go to 2 sided, but with the size I should be able to keep it as-is?).

I use an 8 bulb T5 fixture which perfectly covers entire screen as it is a 23x23 inch fixture. I am using 3,000K T5 bulbs (24W each). So my screen is 484 sq inches, my flow is easily 50GPH (I have ball valve and have tried many different flow rates) and my lighting is approx 200W of T5 / 3,000K. The waterfall pipe sits in the middle of the 6 inch deep scrubber box, so basically 3 inches from light source, as I put T5 fixture right against scrubber unit. I gravity drain scrubber unit back to sump via 1.5 inch drain. If I ever get this thing working, I plan to post pix of design / operation.

I have had this up and running since Dec 22, 2009 and at most I get a very light brown algae coverage. Almost as if it is just detritus or even diatoms? It is NOT the dark brown/ black I have read of others growing. It is not oily....

I have had a GHA problem in MDT (280 gallon) for 6+ months now which is why I set this up. I can say the GHA in MDT has seemed to come to a stand still (not diminishing but not growing at rate it use to). I have read the FAQ of how to kick start an ATS and that did not help. The first 2 weeks of operation, I cleaned screen every 7 days even though no growth to speak of, but have not cleaned now for 2 weeks.

If it is not a flow issue (again, I have throttled back flow through probably 30GPH per inch through current rate of 50-60 GPH per inch), not a screen issue (SM created) and presumably not a lighting issue (I have tried keeping light source everywhere from 3-5 inches from screen), and I know I have nutrients in MDT to feed GHA on ATS, then why won't it grow?

Any help or advise would be greatly appreciated!

Odd. There is just no way that thing can't grow. Even with a display full of algae. Go ahead and post pics of the display and scrubber. Get some good ones of the longest GHA in the display, and let's see how close they are to the light and flow.

2 pictures of unit on day 1. The little pieces of zip tie pieces you see at waterfall pipe slot are to wedge mesh against back of waterfall pipe slot to help flow to front face of mesh since single sided application

[attachment=2:2d7ep7qe]newq.jpg[/attachment:2d7ep7qe]
[attachment=1:2d7ep7qe]day1q.jpg[/attachment:2d7ep7qe]

next picture is from day 3. Notice the very sophisticated light guard added (black construction paper and painter tape) to exterior of acrylic. Prior to adding, this thing lit up fish room like a Christmas tree including MDT. This picture also shows the mesh light guard I added to keep algae out of slot. Some brown algae growth has appeared, so of course I am excited at this point.

[attachment=0:2d7ep7qe]day3q.jpg[/attachment:2d7ep7qe]

kept taking pictures after day 3, but really no difference ever from day 3 in regards to algae. Next 2 pictures are day 30 (ish). No GHA - although in these pictures you can see that under the mesh light guard there is some dark green/black like growth. It is not thick at all, nor is it oily to the touch. It should be noted that the back side of the mesh basically has identical growth as front side even though I do not light the back side at all (other than reflection from back acrylic wall of unit). That is what makes me think this is really just detritus or diatomes? One of these pictures caught a reflection of me holding the 8 bulb T5 fixture up.

Oops looks like 3 pix max upload - will post another reply following

today (approx day 30):

[attachment=2:32gjvy4n]scrubber - 4 weeksq.jpg[/attachment:32gjvy4n]
[attachment=1:32gjvy4n]4wkq.jpg[/attachment:32gjvy4n]

MDT picture showing GHA as requested. You will notice I do not have a GHA disaster on my hands like I have seen others have the misfortune to have to battle. But I do have it on most rocks. Every week, as part of my weekly water change routine, I pull out the tooth brush and tape it to 1/2 inch siphon tube and send as much as I can to the sewer. So I never really have long flowing algae. It grows in all areas - low flow, right where power head hits rock, semi-shaded area, highest rock in tank, on powrhead (Koralia) intake, etc - anywhere and everywhere. .

[attachment=0:32gjvy4n]mdtq.jpg[/attachment:32gjvy4n]

One last thing I forgot to mention in original post, is that I use macro algae in remote DSB fuge (Chaeto). It use to grow like a weed, but seems to have slowed considerably.

Any advise would be greatly appreciated!

Ok, it's making sense now. I do believe that things are fine, and that it's on its way to working correctly. Since your screen in large in area, the algae that does grow is spread out, and does not have to become very thick (yet) like it does on smaller screens.

Here are the facts:

You have almost nothing in the display: No corals, and few fish; this means light feeding.

Waterchanges are removing nutrients.

Manual removal of display algae is removing nutrients.

Your chaeto is hopefully removing nutrients (and not just trapping food).


So, your screen is ready to kick-in. Do this: Start feeding twice as much; stop water changes; stop manually removing algae; completely remove the chaeto. These changes will get your scrubber working with lots of GHA, which will then drive down the cyano you have on the sand. Take weekly screen pics, before and after each cleaning.