Algae Scrubber Basics

[Randy Holmes-Farley]

OK, thanks.

 

[Floyd R Turbo]

Thanks for keeping me in check

 

[herring_fish]

Stability

Stability

From Dynamic Aquaria “Scrubbers are lighted 12-18 hours a day. They are best kept in the darkness when the light in the tank is at its lightest and nutrient levels are low.”

As you have probably heard before, Dr. Adey’s Algal Turf Scrubber® light periods are promoted, in part, to raise pH and oxygen levels when the display tank lights are off to counter its drop in photosynthesis at night.

Not too much consideration was given to algal rest in the book. There are many studies that have been done to find the “Goldilocks Zone” for lighting. Most of it is on phytoplankton although studies range through most plant types including hair algae. Most of them seem to find the optimal photoperiod to be 18 to 24 hours per day depending on eh species.

Normally, the algae in your scrubber or refugium will adjust to whatever period you use …within reason.

Normally, the most important thing is to properly size the total productive algal mass for your system (at whatever level of efficiency your particular design provides for).

 

[Brummie]

Whereas;

http://drum.lib.umd.edu/bitstream/1903/10392/1/Blersch_umd_0117E_11236.pdf

Lights
Each ATS unit was operated under its own set of two 400W metal halide lights. For all trials, the height of the lights above the ATS bed (typically around 50 cm) was adjusted to yield a light intensity of approximately equivalent intensity at the center of the ATS bed. Incident light averaged 390 (range 240–633) μmol photons m-2 s-1 over the entire ATS bed measured with a quantum flux meter and probe (LI-250 Light Meter and LI-190 Quantum Sensor, LI-COR Biosciences, Lincoln, Nebraska). All units were operated under nearly continuous light (23:1 h light-dark cycle) to maximize production. Water temperature was controlled and maintained within 2°C of ambient (23–26 °C) by activating cooling fans when high.

Page 56

Seems that a lot of the saturation points for algae are around the 400 - 500 umol m-2 s-1 (whatever that means in real life). Quite how or if this applies to LED grow lights is very unclear to me so far.

Note the 23hr lighting statement.

Edit - it would appear that intensities of upto 1200 umol m-2 s-1 may be tolerated with increased growth (albeit at a lower efficiency).

 

[gb530]

Are any of you guys running GFO along with your scrubbers or does the scrubber alone do the job? I feel like I'm stripping out too much PO43- and is too low with both online.

 

[herring_fish]

K.i.s.s.

K.i.s.s.

If the scrubber is properly sized, you should have no problem keeping both you N and P in line, no matter how much you feed or how many fish you have in your tank. Of course, you have to factor how efficient your algae system is but if it is not doing the job, you can normally just increase the effective mass or efficiency. That normally brakes down to 1. adding lighted screen inches (or a bigger clump if there is no screen at all), 2. adding lighting and/or 3. adding turbulence.

If I were to buy a unit now, I would get it slightly over sized and dial back "¦say, the lighting. That is because it would be hard to expand on what is probably a good use of space. You probably can't just make the screen bigger, after the fact, because it won't fit.

On the other hand, if you build it yourself, do just that. Make the screen bigger and/or add more lights.

GFO works fine and if you have yours tuned it great. I have no criticism of it at all. If algae is an add on to some other type of system, then I say learn more about it and ask on those threads.

I feel that you have to figure out what is your primary means of nutrient export. Then learn about that paradigm. When things don't work as well as you had hoped, double down in the way users of that method do it.

If you are committed to using algae as your primary form of nutrient export, adding GFO, vodka, a skimmer, lanthium or anything else (and they all work great) just adds another layer of complexity. My personal opinion is that you should experiment with other methods as "œicing of the cake" ONLY went thinks are working well "¦and do it carefully, one factor at a time.

I harken back to the N/P ratio that can get out of whack and the algae might not work as expected and then you start chasing your tail. I have done that so many times before.

I always have to tell myself, "œJust Keep It Simple!" say it again, repeat.

 

[Brummie]

Thanks for keeping me in check

This may hold a reason for inclusion of a dark period;

http://www.icb.usp.br/~flass/hypnos/vol003/9- Pio Colepicolo.pdf

ABSTRACT
The aspects relating molecular control of the biological clocks to the cellular toxicity and the generation of reactive oxygen species (ROS) in marine algae are presented here in the following topics: (i) quantification data of the major antioxidant enzyme activities, such as superoxide dismutase, catalase and ascorbate peroxidation, aiming to gain a better understanding of the oscillatory levels of oxidative modifications in algal cells, (ii) correlation is made of the biosynthesis of low molecular weight antioxidants, such as carotenoids, melatonin, reduced gluthatione, and (iii) damage to the ROS targets, such as polyunsaturated fatty acids in membranes, proteins and nucleic acids.

The effect of ROS in photosynthetic organisms is exacerbated by excessive illumination. Excessive light energy input may, for instance, increase the levels of excited molecules such as triplet chlorophyll and singlet state O2 (1g), the latter being highly electrophylic and capable of oxidizing many other molecules.

Although the endogenous circadian and exogenously driven daily rhythms of antioxidative enzyme activities and of low molecular weight antioxidants are described in different organisms, the rhythmicity of the antioxidant system in micro and macroalgae has only recently received any significant attention (Figure 1). The activity of SOD in cell- free extracts of L. polyedrum monitored at different times of the day and night was found to be three to fourfold higher during the day. This rhythm continued in cells kept in constant light, indicating that the regulation is attributable to the cellular circadian clock (Colepicolo et al., 1992). Using Western blot techniques we decribed that the extractable levels of SOD protein change in parallel with its activity (Okamoto and Colepicolo, 2001). These experiments thus show that the protein is actually synthesized and destroyed each day, as opposed to what might seem a more economical alternative to the same end, such as inhibition and activation, by phosphorylation, for example.

In summary, the regulation and induction of antioxidants takes place in response to different kinds of environmental stress, such as changes in daylight intensity, nitrate pulses and UV radiation. Levels of antioxidant enzymes and other compounds may vary over the course of a 24 h light-dark cycle. Cellular prediction, orchestrated by the biological clock, of a higher level of oxidative status and, therefore, prompt induction of antioxidant enzymes expression must be critical to control the steady-state levels of ROS, thereby preventing the ensuing oxidative/nitrosative damage. This type of defense mechanism is especially important within subcellular sites highly prone to oxidative stress such as chloroplasts and mitochondria. Consequently, the biological clock mechanisms that control the production of ROS are conceivably of importance in understanding several aspects of susceptibility and temporal cell behavior.

 

[Randy Holmes-Farley]

Thanks.

I know there are many reasons that light dark cycles can be useful. But in terms of the macroalgae that I grow in my refugium, I've just not noticed a difference. I discuss one of the reason in the article below.



Photosynthesis and the Reef Aquarium Part I: Carbon Sources
http://reefkeeping.com/issues/2006-10/rhf/index.php

from it:

Photosynthesis of Algae in Continuous Light vs. Light/Dark Cycles
Interestingly, three marine microalgae, Skeletonema costatum, Phaeocystis globosa and Emiliania huxleyi,24 were studied for their rates of photosynthesis and carbon uptake mechanisms in continuous light vs. those same species in light/dark cycles (12 h on/12 h off and 16 h on/8 h off). The rates of photosynthesis were nearly twice as high with light/dark cycles as with continuous lighting. In two of the species (S. costatum and E. huxleyi), but not the third, the contribution of bicarbonate to the total carbon uptake increased dramatically in light/dark cycles compared to continuous light.

How this result might relate to growth and nutrient uptake in lit refugia where macroalgae are often grown to export nutrients is not known. However, it is a sign that perhaps continuous light is not optimal, in addition to being more expensive.

 

[SantaMonica]

When algae gets more than about 20 mm thick, it creates it's own darkness (self shading), so this probably contributes to the ability to do well in 24 hour light.

 

[Brummie]

When algae gets more than about 20 mm thick, it creates it's own darkness (self shading), so this probably contributes to the ability to do well in 24 hour light.

Probably just me but I don't understand that logic at all, sorry

 

[Brummie]

It's gone a bit quiet on here so I'll just pose a thought I've had with regard to double sided screens. If the light requirement for algae tops out at 1200 umol m-2 s-1,with damage potentially being caused above this wouldn't it be prudent to limit the light to 600 umol m-2 s-1 maximum just after cleaning. I found that light could be limiting after 4 or 5 days growth so this may be the ideal time to up the intensity. I certainly found that the one side cleaning seemed to grow algae faster which allowed maximum light all of the time (but twice the cleaning maintenance).

 

[hobbzz]

I'm having problems with my scrubber. I'm pretty sure what it is, but I'm hesitant to do what I think needs to be done. I started it about 6 months ago. After it was broken in and going strong it and my skimmer kept my nitrates at 0 for about 3 months, without any water changes. Then I got really busy with the house and work and didn't scrape it for about 3-4 weeks. When I did get around to scraping it, there was a slimy, clear substance on it, and not much algae. I took that to be algae die off. My nitrates had climbed to about 30.

Since then, which was about 5-6 weeks ago, I have been scraping it every 7 days. I did however, cut back my feeding by about 25-50%. Probably about 35% on average. Now my nitrates have been steadily climging. About 5-10 ppm per week with the current feeding schedule, and are at 20ppm as of today.

Considering the scrubber was handling everything before the die off, should I increase my feeding regimen back to what it was sized for? Would that allow the algae to grow in enough to take care of the extra nitrates? Thanks in advance.

 

[Floyd R Turbo]

Pics of the screen, sump, tank, etc would be helpful. Sometimes this can help to explain things more.

I would say that if you are not getting a ton of growth, don't clean every 7 days, clean every 10 days. If you can, provide info for each pic such as "x days after cleaning"

What kind of lights are you using?

What daily photoperiod do you run?

How big is the screen?

How much flow (total)?

I would not feed more as you have nutrients that should be able to support growth. Something else is amiss here

 

[hobbzz]

I'll have to take pics tomorrow as I'm about to go to bed, have to get up for work at 5am. The size and flow are according to the revised method starting on post 3251. IIRC 14 inches by 6.5-7 inches. ~490 gph measured. Lit on one side for 12 hours, 10pm to 10am, 26 actual watts of compact fluorescent (2 13w bulbs to cover the 14" better). 5100k or 6500k, can't recall off hand. Sized for 4 cubes/day as per your recommendation, now I feed the equivalent of 2-3/day.

What kind of pics of the display tank are you looking for?

Like I said it was working great for about 3 months. Now the exact same setup, hasn't been working since month 4, which was before the bulbs should have been changed IIRC. Thanks Floyd, I'll get the pics up tomorrow afternoon.

 

[SantaMonica]

Sounds like a lot of the growth particles let go and floated around the tank, and are slowly dying and putting nutrients into the water.

 

[Floyd R Turbo]

I'll have to take pics tomorrow as I'm about to go to bed, have to get up for work at 5am. The size and flow are according to the revised method starting on post 3251. IIRC 14 inches by 6.5-7 inches. ~490 gph measured. Lit on one side for 12 hours, 10pm to 10am, 26 actual watts of compact fluorescent (2 13w bulbs to cover the 14" better). 5100k or 6500k, can't recall off hand. Sized for 4 cubes/day as per your recommendation, now I feed the equivalent of 2-3/day.

What kind of pics of the display tank are you looking for?

Like I said it was working great for about 3 months. Now the exact same setup, hasn't been working since month 4, which was before the bulbs should have been changed IIRC. Thanks Floyd, I'll get the pics up tomorrow afternoon.

Just a full tank shot, just to give me an idea of what is in your system. It might not matter, but you never know what I might see. But letting it go that long probably allowed the lower layers to die off and everything detached. When I let a screen go past 16-18 days, when I clean it, it's pretty much all detaches and the screen starts over, partially at least. So you might be seeing this, and cleaning every 7 days is not allowing it to restart. But I wanted to see pics in case there is something else.

Also your lamp temp is not ideal, you want 3000K or 2700K if you can get it, 5000K-6000K will work but is not the best spectrum for algae scrubbers.

 

[hobbzz]

Sounds like a lot of the growth particles let go and floated around the tank, and are slowly dying and putting nutrients into the water.

I've changed 100% of the water since then.

 

[hobbzz]

Just a full tank shot, just to give me an idea of what is in your system. It might not matter, but you never know what I might see. But letting it go that long probably allowed the lower layers to die off and everything detached. When I let a screen go past 16-18 days, when I clean it, it's pretty much all detaches and the screen starts over, partially at least. So you might be seeing this, and cleaning every 7 days is not allowing it to restart. But I wanted to see pics in case there is something else.

Also your lamp temp is not ideal, you want 3000K or 2700K if you can get it, 5000K-6000K will work but is not the best spectrum for algae scrubbers.

Lights are actually 2700k. This should be about 7 days. Here are the pics.

 

[Floyd R Turbo]

With screen growth like that at 7 days, the most I would do is swipe off the gooey stuff (the red slime) with a credit card (not a forward-angle scrape, just 'drag' it across the screen) and maybe a light rinse to remove any loose algae. Leave everything else on the screen. This is the method I follow when I can still see the screen material, as I can see in your pics.

In my opinion, there is really not a hard-and-fast 7-day cleaning rule, it is all subjective based on your results. Cleaning should be done at a time when the growth is thick enough such that it will start blocking light to the base of the screen. You don't want that to happen, or else you will have detachment and re-starting. So the trick is to let the screen grow as long as it can without hitting that death point.

In your case, if this is 7 days growth (and single sided) then I would do the drag & rinse cleaning, and let it grow for at least 4 more days if not 7. But the factor that you have to take into account here is the single-sided screen: because of the lack of light on the back side, the base of the screen will start to die that much quicker when it gets shaded. To counter this, you might consider bumping up the CFLs from 13W to 18W. Also you have your lights at an angle which is not ideal but probably not hurting anything too badly. After all it was working. If you increase the light level, you might start getting lighter and yellower growth, which tells you that you need to increase flow or back down the photoperiod.

Start simple though, do intermediate cleanings. You can always do a partial cleaning also and only scrape in a pattern such as a tic-tac-toe or crosshatch

 

[hobbzz]

Thanks Floyd. I'm in the process of setting up a 120g fuge, and the ATS will feed it. So when that's up and running I'll be able to position the lights at a 90 degree angle. I'll start with the light scrape, monitor and go from there. Thanks for the help.