The scrubber is only lit on one side, and that's definitely a a good thought that the light wasn't strong enough to grow enough algae to lower phosphate. I tried testing that a couple months back by mounting the 10k power compact bulb from my bc29 against the back middle scrubber section along with the cheap amazon led lights. I saw greener growth but the phosphate reduction did not improve......
Bulk Reef Supply just posted a video testing scrubbers using clear water scrubber and had similar results with phosphate reduction becoming limited after several weeks of low nitrate. I would like to see a test where nitrate is dosed into these low nitrogen systems to see if it keeps the phosphate reduction rate of scrubbers from reaching capacity
Hi Sami;
you're basing your PO4 argument on (1.) experience running a scrubber for 7 months, a scrubber with sub-optimal lighting. I built my first scrubber in
1995, and my present tank has run a modern downflow scrubber, with lighting intensity & spectrum tuned to the unit, for near
4 years. And I have done the tests over this period.
And (2.) on a substandard BRS test performed over
7 weeks.
The BRS test gave little information, and none on screen size, photo-period, or whether the scrubber screen was virgin or had a mature – healthy - growth of algae. I could point out various faults with their test, but I'll stick with PO4.
What else could have affected their PO4 results? On this I would ask why they didn't do the simple targeted test on an aquarium with mature live rock, instead of a tank with dead rock that would impact on the results when it began cycling. The rock would have soaked up PO4 & then released it.
Look at the results for the control tanks that had no filtration, but also had dead rock.
Neither Control tank #1 or #2 when fed 1 cube a day over the 4 week period, had a rise in PO4 between weeks 2 to 3?
Again, when fed 2 cubes a day over a three week period, neither Control tank #1 & #2 had any rise in PO4 between weeks 4 to 6? Why,,, how,,, no filtration!
The control tanks PO4 readings over the 7 week period somewhat mimicked the scrubbed tanks readings in regards to an increase in PO4 after the 2 to 3 week, & 4 to 6 week periods, although the control tanks PO4 went way higher. Something else affected the PO4 levels, & I say it was the dead rock used in all four tanks.
I base this on the tests I have done on my own aquarium over the 4 year period it has had the scrubber running. My aquarium was 3 to 4 years old by the time I fitted the scrubber. I had previously discovered that I had NO3 at well over 60ppm & PO4 at 100 times the recommended level of 0.03ppm. After the scrubber matured I quickly removed the skimmer, & Marine Pure 8x8, & have ran my aquarium using a scrubber only, with occasional GAC, & very occasional partial water changes. I can run NO3 at zero, or as high as I want it by varying the length of the photo-period.
My PO4 readings, using Salifert, & now RedSea, have never been over 0.03, unless I dosed Potassium Phosphate. The level I run No3 at has had no effect on PO4 levels. This is the same for two other aquariums I built scrubbers for.
Bulk Reef's test was to see if a scrubber could outperform a skimmer in regards to controlling inorganic nutrient export. I could have told them, yes, easy. BRS should have used an established aquarium that used a skimmer - removed the skimmer & replaced it with a scrubber with a mature screen.
Now BRS is going to test (the same tanks) to see if a scrubber can keep the rock work pristine. What they need to do here is use an aquarium with GHA growing, then fit a suitable mature scrubber to the tank. I've done it. After a month the GHA & cyano on my rocks disappeared, directly due to the scrubber. But the rock work won't stay pristine - mine then ended up covered in coralline.
Cheers.
