Filtration Lighting L2 8 weeks growth, lighting adjustment?

Starting to look a lot better, I would say you can either 1) up the intensity to 4 o'clock or 2) add hours (go to 14-16) but since your nutrients are low and it's taken some time to get to this point, I would proceed slowly - maybe just go to 14 hours/day and give it another growth cycle to confirm.

 

Swipe the slime off & rinse, leave any GHA behind and let it go for a full growth cycle.

 

That's developing nicely. You can prune growth a bit, just using your thumb & forefinger to remove about 1/4 to 1/3 of the growth, then rub & rinse. This will help to ensure that light and water get to the base of the screen.

Also, you're at a relatively low intensity, so the light is not going to penetrate very deeply - another reason to do a pruning or partial harvest. I would normally suggest that you increase the intensity, but with caution in your case, due to the low nutrients. The higher intensity is going to allow you to let it grow longer, the thicker growth needs more light intensity in order for it to penetrate into the base. So what you might do is wait 2-3 days for growth to bounce back from the pruning, then increase the intensity to 4. After you prune again, go back to 5 for a few days, then up again. The idea here is to not over-light when there is less growth, but not under-light once it gets thicker.

If that's too much trouble, you can try turning it to 4 and see what happens. Or, I might be over-thinking it, and you'll be fine where you're at on intensity.

Glad to see that yellow growth fading away.

 

I forgot about that

This should happen over time, but now that you have a solid base of GHA on the screen, I go back to this comment

So now you're here:

Given the tank algae issue, maybe it is time to push it a bit harder...there's still nutrients available for the algae on the rocks. Go to 4 o'clock and 16 hours/day. That's not a major increase, so you should be OK

Keep using the technique of "dragging" the toothbrush across the growth weekly & rinsing, and then add in pruning 1/3 to 1/4 of the growth. If this continues to improve scrubber growth, you should see a reduction in tank algae. If you see better scrubber growth, but the tank algae is about the same, extend hours to 18-20.

 

I would just change one thing at a time. Use the scrubber to help get the tank algae eradicated, then give it a few months to allow things to adjust to the change in filtration. Then you can start dialing back the skimmer if you want, or you might find that scrubber + skimmer works well for what you keep

 

I would hold the course with those settings for a couple more cycles of growth. This time, remove the screen 1/2 way through the growth cycle and give it a rinse to remove any of that dark growth that I see in the 1st pic, that stuff usually wipes off pretty easily. Otherwise, try not to remove much. Then put back in for the rest of the growth period.

You might do this twice before actually harvesting anything, so 1 week, then prune, 1 more week, prune, 1 more week then harvest

 

That's looking a lot better, sometimes slow and steady is what you need. I'd keep doing what you're doing!

 

I don't know that I would say you're doing anything "wrong" necessarily. I scanned the thread and if you are still feeding flake and pellets daily, and 1-2 cubes/week, that likely comes out to 1 cube/day or less on average. So you might have a bit of an imbalance when it comes to nutrients being delivered to the scrubber compared to the light you are applying to it.

The yellow growth typically shows up when you have too much light and not enough nutrients. In looking back at my other posts, at some point I said if you have OK growth but still have tank algae, to extend hours. The problem with that is that your tank algae might be showing up as you reduce nutrients and things like phosphate start to leech out of the rock and into the water column - the algae is being fueled by that. In the long term, that's a good thing. But it's a slow process to get past that issue (bound phosphate) so this is a marathon vs a race, meaning you can't in some cases "push" the scrubber to make things happen faster. I wonder if maybe this is the case here.

Intensity is the instantaneous factor - if you have low nutrient water and are feeding moderately to conservatively, then you push the intensity up, you might be seeing the effect of too much light/not enough nutrients.

You can lower the intensity, and try to match things better with the nutrients available on an instantaneous level (technically, what you're trying to balance is # of photons with # of nutrients, basically) and then you can extend hours to draw out the filtration longer. This should produce the same or similar overall level of filtration activity, it just does it over a longer daily period (compared to very high intensity for a short period) if that makes sense.

So if you're at 18 hours/day at 4 o'clock still, try 22 hours/day at 5 o'clock. 4 isn't overly intense for most cases, but I'm wondering if in this case, where you're not feeding a ton, that the balance is off a bit and that's why the yellow stuff is showing up.

On the other hand, what really matters is "how is your tank doing"...if your tank is doing well, it really doesn't matter a whole lot what exact type of algae you are growing, as long as it's doing the job. Some corals might not "like" the presence of the yellow slime algae being in the system, but if you're not seeing any adverse effects, it might not be a big concern.

Fill in any other details about your system that might be pertinent - I'm making a fair amount of assumptions here.