New L4

I can't quite tell from that pic but it looks like a dark coating on the screen?

It's best to take a flash picture inside, that usually shows up the best

Ok now I see the pics from the 2nd post, that's what you might expect to see after the first week, kind of a diatom coating. I would let it run for at least 2 weeks before touching the screen. It's hard to draw any kind of conclusion until you give it at least 2 weeks

What intensity setting are the lights at? What is your daily photoperiod?

 

You've got some sprigs of GHA on there actually, very dark but where you can see the screen holes blocked up, that's GHA growing.

Did you clean it at all? I would not have but let me know if you did.

As long as you didn't clean it, increase to 18 hours and set it to 5 o'clock for sure. Leave it there for a week.

 

I would say yes, if the pictures you posted last are post-cleaning, that's looking like a good start. Go to 18 hours and 5 o'clock, then I would try to leave it for a week or 10 days. When you look at the growth, you can slide one fixture sideways, turn the lights off, and shine a white flashlight at it. The GHA shows up as black under the scrubber lights because there is no green component to reflect that color. I would expect that after 10-14 days you should see full coverage, but you might just have clumps of GHA, some that get pretty big. If that happens you will just want to pick away at the clumps to thin them out and rinse lightly again (in 10-14 days, 14 if you can)

 

I would only rub & rinse, if anything. I would expect half of the growth to come off when you do that which is fine.

You could also leave alone and let it grow for a few more days, and increase the hours a bit, and maybe the intensity too (to drive the light deeper into the growth)

That's fantastic growth for 9 days!!!

 

What's your light intensity at? Still 5? Looks like the dark growth is blocking light, do you have relatively high nutrients?

I would say increase intensity to 3, maybe 2 even...but wait 3-4 days, looks like the growth got thick and the base died back. Crud. Should have had you increase light a few days after the last harvest

 

I was looking at the pics on my phone last night in bed, now that I look at them on a full size monitor I can see that dark slime more clearly

I've had that type of growth before - it's typically a phase but can last a while. It is really stinky/pungent, I parallel that smell to Anthelia (waving hand coral) when removed from the water. It usually it very weakly attached and breaks up (dissolved) when you touch it or swipe your hand across it. Once you swipe it off and rinse it down the sink, the smell goes away relatively quickly.

When you are getting that type of growth, the result is typically what you see - it does tend to block the light, but at the same time it's rather thin so some light does get through. I first really encountered it when I was running my first UAS, it almost completely dominated the growth (underwater) and took a long time for GHA to take over and for it to pass. I had it on my first waterfall LED scrubber as well, but it was less of a problem. I can't quite pinpoint what causes it, but it seems like it's the high-intensity of LEDs that it favors. But there's likely some other chemistry going on that causes it to "thrive" - although I wouldn't say it's anything that is going to dominate, especially with the GHA growth you are getting.

So given the condition of your scrubber - which is good, healthy GHA - I believe the answer is higher intensity light, and time. The higher intensity light will keep the algae mat in tact (the light will "punch through" the dark slime) so that you can eventually get past this phase.

But as I mentioned in my last post, you will want to give the screen a few days to recover from the harvest, when you have the dark slime and low(er) intensity light, the roots started to die off a bit and you were left with a rather bare screen. That is partly due to the dark slime/shading effect, and partly because the screen is still very new and you have only minimal attachment remaining (but there is still plenty, I can see green sprigs all over in that pic).

So leave the intensity at 5 (assuming that's still where it is) and then check on it in a few days. As long as you have growth happening (which you should) then bump the intensity up one level at 3 days in, then give it 2 more days and check it again. As long as you are still getting GHA base growth, kick it up again (to about 3 or so).

At about day 6 or 7, take the screen out and swipe and rinse to get rid of the dark slime.

Let it grow about 10 days and then give it a light cleaning - only remove maybe half of the growth along with any slime, and then put the screen back in and leave the intensity at about 3 (or wherever you had it prior to cleaning) and then put back in action. Let it grow for 4 or 6 days then swipe the slime off, then let it continue to grow until day 10.

You might have to follow this above process for a while until the slime goes away. Like I said my experience is that it is a phase but it will pass, or become much less prevalent over time. It may go on for months, but as long as you only have "streaks" of the dark slime with good thick GHA underneath 9and not a full coating of the dark slime) then you don't really have to do the interim swipe process - just let it grow and ignore the dark slime at that point.

Hope that helps
Bud