Scrubber build

I have a thought, and it's a result of a convo I had last night with a customer of mine in Serbia. For years he has been fighting a similar battle, except his was a bit worse. He experienced one of the few cases of "whiting" that I've seen, and the only one that persisted. What happened with him is that he would start to get growth going, and then it would suddenly turn white (overnight, in a 24 hr span, etc). He would have to repeatedly start over. It was on a relatively new tank at first, but persisted for years, constantly recurring. He had algae that would occasionally pop up in the tank, get fought back when the scrubber got going, and come back when the scrubber died off.

When he cut back his DT lighting time and intensity little by little over time, the scrubber started to grow better. He now has the scrubber working great, no algae in the DT

That leaves me with my question to you: is it possible that your LEDs over your tank are running too intense and/or for too long? I've seen people in the past who have adjusted their LED DT lights to their liking (appearance) and it ends up being a set point that causes the DT to get so much light that it can actually tend to out-compete the scrubber.

I don't want to assume your knowledge of tank lighting, but from what I understand, even SPS corals will do well under reduced lighting scenarios. When I say "reduced" I mean that if you are running and overly long and intense lighting scenario on a daily basis, and you cut back the photoperiod significantly (like going from 16 hours/day to 10 hours/day) and reduce the peak time (for example from a 3 hour high-intensity peak to a 1 hour peak), the corals will do just fine

What is your DT lighting scheme?

 

Most definitely you can have too much flow. In fact, I’ve pretty much concluded that the 35 GPH/in guideline is more likely the maximum for most people, not the target.

In your situation, I think pushing 50 GPH/in would fall under “trying to force it”

Dial it back to 35 GPH/in at the most. Really all you need is enough flow to provide full coverage of the screen, and then maybe a little more after the screen matures.

 

I'm working on a universal solution for the issue of flow distribution both one side vs the other and one end vs the other. Side/side distribution has to do with how the screen sits in the slot, if the slot pipe is rotated a bit, this tends to cut off flow to one side. Also, if the screen is "warped" this can happen as well. My idea easily solves that and adapts to any slot pipe.

The end-to-end distribution is a bit trickier. If you set the flow such that there is just enough flow to cause even coverage, this is good for starting up and for some, this is all you'll even need. Flow can be increased through a range that is generally up to that 30-35 GPH/in rate and the flow will start even, and if you have regular growth, it usually will - sometimes it will be uneven right after you harvest, but growth filling in tends to cause it to even out over time.

Regarding the 50 GPH/in, you are correct, my Rev 3 "HF" was geared towards the idea that if you secure the slot pipe in place firmly, you can really increase the flow without worrying that the slot pipe was literally going to take off like a jet and spray everywhere in your sump. But what happened is that I had a few people who had great results with super-high flow, but that was the exception (at least from the very little feedback I got). One person even had a reduction in growth, and the growth was more slimy - and this was on a large tank, so there wasn't a nutrient supply problem. Other issues at that high of a flow rate are 1) arcing of the flow and 2) noise. So I abandoned that idea as a general recommendation but I still reserve it as a possibility, but it's really "try it, this might work for your system in your situation" type of thing now.

There is still the balance factor - the idea is that you want to find a balance of flow, light intensity, and light duration that sync with your tank's nutrient levels. There is usually a wide range of operation, but you might be on the far end of that range.

I suspect that if you have tank algae but no nutrient issue, then the answer is to dial back the flow and also dial back the intensity, but extend the duration. The original idea purported by SM was that higher intensity for a shorter time is better than lower intensity for a longer time. That's why the rule of "CFLs a X watts per sq in for 18 hrs/day" changed to "CFLs for 2X wattts poer sq in for 9 hrs/day", or rather why that became an option (the higher intensity)

But LEDs are different, and Reds and Blues hit the most excitable peaks of photosynthesis and they hit them hard, so if you can't support that level of photosynthesis because your intensity is too high (and the nutrient stream is low) then you're going to see some issues start to pop up. So if you back down the intensity, you lower the photosynthetic level down below the "hyper excited" level, and then you can draw out the hours.

 

I'm not sure how your pipe is configured, next time to clean it, get some up-close shots if you don't mind!

 

With the type of growth you have, I’m wondering if you’re getting a little detachment.

 

It looks like you have a mixed bed of growth, some of it is GHA and some is Ulva. The Ulva may tear away more easily. I had one customer who could grow nothing but ulva, and it detached very easily, he hated it. Then there's @atoll who prefers to grow that.

 

It does look like a form of Ulva to me, at least in the pics. Looks more ribbon-like instead of hair-like. But it also looks like there is something else mixed in with it. If you have the ability, take a mesh media bag and place it around the outlet of the scrubber and see if you catch anything. You might be having some detachment but it finds it's way back into the system and gets consumed, so you never see it.

Regarding the yellowish stuff, you really don't have that much of it, and it's not all that uncommon to get some of this type of growth intermittently. I would not be concerned.