Scrubber settings end state goal?

[b4tn]

I know this is pretty general but I am trying to figure out how to find the sweet spot between running a system too clean and not clean enough. I have 70 gallons of water volume with plenty of rock and running a Reef octo 150 skimmer 24/7, Carbon reactor 24/7 and my L2 scrubber which runs 24/7 with light reverse cycle 9 hours, flow is pretty much all the way up, and intensity is at 5 oclock on the dial. Its only been back on line for about 3 weeks and when I cleaned it the other day I had some nice even dark green algae growth firmly attached to the screen.

So the question is what is the goal end state for light intensity and duration? I am pretty sure I could bump intensity and duration as is but do I need to? I currently am not getting any Po4 or No3 readings. I have the following livestock

One spot foxface
Yellow tang
Coral beauty
Corris wrasse
2 clowns
2x hand sized brittle stars
sea cucumber
100's of micro brittle stars
Enough encrusting SPS to consume 1 dkh of alk daily

I feed the equivalent of 1 cube a day of home made fish food, several pinches of pellets, and the occasional 1/4 nori sheet. I also dose zooplankton every 4 days with my skimmer off at night.

 

[Flippers4pups]

The main reason for a ATS or refugium is for a natural nutrient export. We use these typically to reduce N03 (Nitrate) and P04 (phosphate).

If you have little or no nutrients, it may be difficult to sustain growth for your corals, as well as the algae in the scrubber.

 

[b4tn]

Nutrients are not zero when the scrubber is off. That’s why the question. Do I continue to turn the scrubber light intensity up? Increase photoperiod? Or leave it alone since nutrients are not reading now. I’m curious what others that have similar biolaod have theirs set at.

 

[Reefcowboy]

I have been running an ATS for 9 months now. I scratched my head for the first two-three months when I got little to no algae and the algae was like black goo.

My system is a 150 sps with about 15 fish, among tangs, clowns, cardinals, foxface. I run my ats leds about 10 hrs per night. I feed very heavy, about 10 cubes of varied frozen foods along with many pellet feedings on an auto feeder. My nitrates are around 4ppm wich is where I need it. PO4 zero.

I would wait longer as ATS will do really well once established. 3 weeks it will be seeded, but not long enough to be harvested. I would look at the algae coloration, if it is bleached or dying, it could be signs of too much light intensity. I would also check nitrate levels as if you are not feeding enough, the algae could starve and not grow as fast.

I reduced the hours of photoperiod because my nitrates were dropping below 1ppm.

 

[Turbo's Aquatics]

L2 scrubber which runs 24/7 with light reverse cycle 9 hours, flow is pretty much all the way up, and intensity is at 5 oclock on the dial. Its only been back on line for about 3 weeks and when I cleaned it the other day I had some nice even dark green algae growth firmly attached to the screen.

Do I continue to turn the scrubber light intensity up? Increase photoperiod?

Just double checking - in the latter comment you ask about increasing the photoperiod, but in the first post you mention that you are already running them 24/7?

For reference: The light intensity at around the 6 position is the starting point (and is about 25% of the max). Turning up 1/4 turn doubles the intensity (50%). Turning up another 1/4 turn (to 100% full power) doubles the intensity again (4x the 6:00 position).

What I recommend is starting with 6:00 intensity and 9-12 hrs/day duration, and with just enough flow to cover the majority of the screen without getting "arcing" of the water flow. You don't need tons of flow, and initially, you don't want that (it can prevent algae from easily attaching). I think you are beyond this point, so that's mainly for everyone else reading in case they have similar questions

Ramp up the scrubber over time until you get to the operating point that works best for your system. After you get some GHA growth (usually within the first 2-3 weeks) jump the intensity up 1 notch. Wait 1 growth cycle, then add 2-3 hrs/day to the photoperiod. Keep alternating between adding intensity and hours until you get to the 50% spot (I switched potentiometers in January, so this is 3:00 for pre-Jan 2019, 9:00 for post-Jan 2019) and about 16-18 hrs/day. Hold it there for at least 2 growth cycles. If you need more, continue adding intensity/hours as before. You may need to increase flow at some point in order to deliver nutrients faster at higher intensity.

Intensity increases the "instantaneous" adsorption rate. If your rate of nutrients to the scrubber (which is a blend of available nutrients and flow rate) gets too low, that's when you start to see gooey yellow growth, or even algae starting to turn white (which can happen overnight in rare cases). This is an indication of needing back off intensity.

Duration has less of an impact; increasing duration just draws out the adsorption period at that given rate. So if you find an intensity sweet spot that grows algae nicely, you can leave it there and keep increasing hours. In fact, it's not a bad idea to hold at 50% (3 or 9) and then add hours every growth cycle until you get to 24/7, then only add intensity if needed (need more uptake/growth)

There are a couple ways to deal with avoiding dropping the nutrients too low. 1) run long hours at mid-range intensity (so around 50%, maybe a bit on either side of that) or 2) run high intensity for shorter hours.

Higher intensity allows for you to let the algae growth cycle go longer, because as the algae gets thicker, you will want intensity to drive that light deeper into the mat of algae and keep it from breaking down at the base (screen attachment). If you're running around the 50% intensity, you should not have an issue with rampant detachment

Nutrients are not zero when the scrubber is off.

Are you saying that you see a difference in tests in the same day when the scrubber lights are on vs off, or are you saying that when you were not running the scrubber on the tank, you had measurable nutrients? Thinking it's the latter but just making sure

 

[b4tn]

When I said It runs 24/7 I mean the flow is always on. The lights are controlled with my controller.

But that answered all of my questions! Thank you! I am getting good growth right now. My scrubber is pre 2019 and I have the light dial between 4 and 5 with a duration of 10 hours. I will leave it for a couple weeks and see how it goes.