Algae Scrubber Basics

[gb530]

Hey Floyd,

What is the best photo period in your opinion? 12/12, 18/6, 24 hrs? I am sure its in this thread somewhere but finding it in 235 pages would take forever, haha.

I noticed you mentioned photo-saturating and that it can have negative affects. I currently have mine at 18 hours on and was thinking about moving it to 24 hours. Thoughts?

 

[Floyd R Turbo]

All plant life needs a dark period, so there is good reason for not doing 24/7. 22 would be the absolute max IMO.

Photoinhibition happens when you have light that is too intense, and is more indirectly related to duration. Meaning if you have too powerful of a light source, it will just inhibit from the start and you'll never get growth (regardless of duration). If it's borderline too much, breaking up the photoperiod throughout the day can help get started, but adding a diffuser reduces the intensity until the screen gets mature, then you can hit it with the higher intensity light. So if you are running 18 hrs now and not getting bare spots (i.e. your screen is mature) then photoinhibition is not a concern.

But back to your question, what is the best photoperiod, really it is what works for your system. To many factors to pin it down for everyone, because everyone's setup is different, and recommendations would change for different sources as well as different implementations.

I can answer questions about your specific system a lot easier than trying to make all-in-one guidelines, that's what I'm here for. If you want to post pics and info about your scrubber I might be able to help you tweak it. Are you having issues with it, is that why you want to bump up the photoperiod?

 

[gb530]

All plant life needs a dark period, so there is good reason for not doing 24/7. 22 would be the absolute max IMO.

Photoinhibition happens when you have light that is too intense, and is more indirectly related to duration. Meaning if you have too powerful of a light source, it will just inhibit from the start and you'll never get growth (regardless of duration). If it's borderline too much, breaking up the photoperiod throughout the day can help get started, but adding a diffuser reduces the intensity until the screen gets mature, then you can hit it with the higher intensity light. So if you are running 18 hrs now and not getting bare spots (i.e. your screen is mature) then photoinhibition is not a concern.

But back to your question, what is the best photoperiod, really it is what works for your system. To many factors to pin it down for everyone, because everyone's setup is different, and recommendations would change for different sources as well as different implementations.

I can answer questions about your specific system a lot easier than trying to make all-in-one guidelines, that's what I'm here for. If you want to post pics and info about your scrubber I might be able to help you tweak it. Are you having issues with it, is that why you want to bump up the photoperiod?

Thank you for the detailed response.

Not having any problems in regards to the scrubber and it is quite mature, it has been on my tank for about 5 months now. I pull a handful of algae off it every 2 weeks and since setting it up my nitrates are at dead zero!

I wanted to set it up 24/7 to lessen pH swings.

Here's a pic of my scrubber at about 2 months

Here's a video of it when I first set it up!
<iframe width="853" height="480" src="//www.youtube.com/embed/Zt-PCodTdgw" frameborder="0" allowfullscreen></iframe>

 

[Floyd R Turbo]

I think I remember yours now. Looks good! If you want, you could cut the lights for one hour at 4 times throughout the day instead of one large block of 4 hours. The might help your pH issue.

Your DT lights should keep your pH up during the day, so if you have the scrubber on reverse cycle, you shouldn't have a pH problem really. The key is keeping things consistent, and in the case of pH, that would mean a regular pattern. So if there are dips and peaks throughout the day's cycle, as long as that is the way it always is, no big deal. If it's erratic and irregular, that can be a problem. Some corals might not respond well to a particular regular pattern, but that's a whole 'nother issue

 

[gb530]

I think I remember yours now. Looks good! If you want, you could cut the lights for one hour at 4 times throughout the day instead of one large block of 4 hours. The might help your pH issue.

Your DT lights should keep your pH up during the day, so if you have the scrubber on reverse cycle, you shouldn't have a pH problem really. The key is keeping things consistent, and in the case of pH, that would mean a regular pattern. So if there are dips and peaks throughout the day's cycle, as long as that is the way it always is, no big deal. If it's erratic and irregular, that can be a problem. Some corals might not respond well to a particular regular pattern, but that's a whole 'nother issue

For sure, thanks for all the input! I think I'm going to stick with it at 18hrs on, just wanted to get some feedback from you and this helped a lot.

 

[cubfanmatt]

Hey Floyd,
You suggested a diffuser on my light a couple of months ago and has it really helped with getting growth over the entire screen. So that problem has been solved, thanks! I am getting good growth but it takes 4 weeks to get what others seem to achieve in 1-2 weeks. I am wondering if I am getting the most out of my scrubber. Any thoughts or info you need to help me diagnose the issue?

Thanks!

 

[Floyd R Turbo]

Glad to hear my advice worked! Always good to have feedback like that

Now that you have growth over the entire screen, you might try removing the diffusers. Lowering the intensity is mainly needed during the maturing phase, once the holes are filled in, the screen can "accept" a lot higher intensity light.

 

[cubfanmatt]

Wow, I didn't expect to hear that! Thanks again!

 

[Floyd R Turbo]

The first step in starting a scrubber is to let it mature. Once the holes fill in with growth that doesn't come out when you scrape the screen, then you have more post-cleaning algae left on the screen to absorb the incident light.

On a new screen, there is less "competition" for energy from the light, so whatever algae is there can end up getting too much, and that is where photoinhibition starts to take place. I used to refer to this as photosaturation but technically that's not correct. Photosaturation happens pretty fast, because the photosynthesis cycle (in simplified terms) is basically two steps, one is "filling the pot" with energy from light, and the second is "emptying the pot" - which is a "dark" process. If you really want to dig into it and learn, I think you can google "photosynthesis dark cycle" or "reaction" and read up on the Calvin Cycle. There were studies done back in the 1930s or so by Dr. Otto Warburg that showed that you could get the same photosynthetic production by "flashing" the light (using a slotted rotating wheel) as you could with constant light. Further studies proved that you could make the dark period 10x longer than the light period and get the same results as constant light, with the frequency of flashing being rather high, in the kHz range if I recall. My contention is that with the water flow (whether that is from waterfall action or bubble traveling upward across a vertically oriented unit), we already get a fair amount of this type of flashing action - similar to how you see focused light patterns on the bottom of a pool in bright sunlight (this was actually studied in reef pools in the ocean to show that the varying intensity waves caused this type of "flashing" on corals and increased zooxanthellae energy production).

Anyways, that was a quick description of what photosaturation is. Photoinhibition is sort of like photosaturation taken to the extreme (again, simplified explanation). So once you get a base of growth started, then there is more algae (post-cleaning) to "compete" for the light energy available, and while there might still be some short-term inhibition, over the course of the growth cycle that will not last very long.

The kicker is that each system is different, so removing the diffusers might cause your setup to revert back a bit, depending on available nutrient and flow, and also how well your algae is anchored to the substrate.

I have left screens to grow way too long and had detachment (usually after 16-18 days) and then when cleaning the screen, almost all the algae comes off, leaving only a speckled/stained look. Even with that little growth, within a few days the growth bounces back and by the end of a week the screen is fully covered again, and by 14 days it's chock full and holes are filled in again after cleaning. That is what I typically find with a very mature screen (6 months+ old) and my theory on this is that the algae have embedded deeper into the screen on a more widespread basis, or perhaps there is a bit of calcification that provides a stronger anchoring ability. New screens do not have this property, so that it why it is important to not over-clean a new screen.

 

[Brummie]

Strange - I thought photosaturation was the limit of maximum photosynthetic production while photoinhibition was an excess, causing damage to PSII faster than it can be repaired. Period.

 

[gb530]

Hey Floyd,
You suggested a diffuser on my light a couple of months ago and has it really helped with getting growth over the entire screen. So that problem has been solved, thanks! I am getting good growth but it takes 4 weeks to get what others seem to achieve in 1-2 weeks. I am wondering if I am getting the most out of my scrubber. Any thoughts or info you need to help me diagnose the issue?

Thanks!

If you have the right light, right flow, and a good surface for the algae to grab I wouldn't be worried. If your scrubber is not producing as much growth as others, it's most likely because your system does not have the nutrients to support it. Which is good! Low nutrients is the goal.

 

[Floyd R Turbo]

Strange - I thought photosaturation was the limit of maximum photosynthetic production while photoinhibition was an excess, causing damage to PSII faster than it can be repaired. Period.

I think you probably are better versed in the exactness than I am, I'm sure I read that also somewhere but it gets lost when I try to regurgitate it while trying to write an intelligent sounding post.

In a way, we're both right. My explanation was sort of a layman's terms way of putting it. On a cellular level, the way I understand it (and maybe I'm still wrecking the term here) photosaturation as I put it is represented by the "pot full". This would be, as you put it, maximum production. So on a mature screen (as a whole, not at the cellular level individually, where there would be variances of saturation levels), where there is enough algae growth to absorb all the incident light (or maybe, as the screen grows, there is not enough to saturate the entire screen) you wouldn't have the damaging level of light that would cause photoinhibition.

On a brand new screen, with the same amount of light, there is no shading and a lot of light from both sides, so this would be a case where you would far exceed the light levels needed for saturation for what algae is present, and that would lead to photoinhibition. Perhaps it would be better to not describe photoinhibition as a "next step" past photosaturation, but rather a "preventer" step, meaning that you can't necessarily "spill over" from photosaturation, but rather you just never even get there at all because of the damage on a cellular level.

Either way you look at it, the result is the same. Too much light on a new screen = no growth. Same amount of light on a mature screen = growth.

Garf, does that sound like a more accurate description?

 

[Brummie]

Not paid too much attention to light quality, intensity and photoperiod upto now to be honest (after all, I use cheap Chinese lights).There is certainly an acclimatisation (growth history) element to algae but from the little I have read on the subject, algae has maximum growth at about 10 to 30% (depending on species) natural sunlight intensity and above about 40% growth is actually reduced. I guess someone should actually work out the ideal theoretical lighting intensity. Floyd, I know you like lights

 

[salty joe]

algae has maximum growth at about 10 to 30% (depending on species) natural sunlight intensity and above about 40% growth is actually reduced.

That's fascinating. Do you know if that would be tropical mid day sun at the surface of the water?

It seems with a PAR meter LEDs could be dialed in to maximize growth/watt.

 

[SantaMonica]

All new scrubbers which use white growth surfaces should have a black cloth placed over the LEDs for the first week or two. Because the all-white interior reflects so much light, when it is new the light levels are way above the highest amount that can grow anything. Once growth starts, the white is covered with growth and the total light levels drop, and the cloth can be removed. Any cloth, stocking, or t-shirt can work.

This covering of the lights can be done by anyone, on any scrubber, even waterfalls. Waterfalls use plastic canvas which has more holes than material, and they are not in white compartments, so the light levels when new are not that high. But it still might help if a new screen stays completely empty.

The reason for a white texture and strings, of course, is too allow more light to reach the base of the growth that does the attaching. As the growth gets thicker, the bottom layers will almost be in darkness, so the white surface doubles the light there by reflecting instead of absorbing the light.

 

[Chris Abbott]

I am still not getting the nice green grout I see on some screen, but luckily what does grow is keeping the nutrients in line. Any diagnosis?

 

[Floyd R Turbo]

All new scrubbers which use white growth surfaces should have a black cloth placed over the LEDs for the first week or two.

I had one LED fixture where I put acrylic diffusers in front of the LED like the ones that are in 2x4 fluorescent ceiling fixtures. It was a DIY array on heat sinks with stand-offs, but the stand-offs were too short so the LEDs were touching the diffuser. I was running reds and a blue in series at 700mA (all of them, at the time). The result was that the blue LED dome actually got hot enough to burn a hole in the acrylic diffuser.

LEDs do give off heat in front of the LED, there is no doubt about that. So I would never ever ever put a cloth, nylon stocking, plastic canvas, etc in a position where it could potentially come in contact with the LED dome. This could be a potential (albeit low) fire hazard.

The safest material, IMO is the acrylic diffuser. It's cheap and relatively easy to cut (make several passes with a box cutter and a straightedge)

 

[Randy Holmes-Farley]

All plant life needs a dark period, so there is good reason for not doing 24/7. 22 would be the absolute max IMO.

Macroalgae "needs" a dark period? What evidence is there of that?

I lit my refugium for years 24/7. Macroalgae grew quite well. Then I switched to a day/night cycle and saw little change. Since the latter was cheaper, I went with it, but it is not so simple as they "need" it, IME.

 

[Jack5746]

I was thinking, with keeping the algae out of the tube, couldnt you just get a bigger tube that would cover about 1/4" down and 1/4 inch away from the screen. Basically a tube inside a bigger tube. May starve the algae closest to the water tube from enough light to not grow up into it....

I did that to mine when I went on vacation for a week, seemed to work well then when I got back I removed it. Now I just take a tooth brush and brush along the pipe slot and screen every morning before leaving for work. Mine is way oversized for my tank. I am using one full screen and four cfl bulbs, two for each side for a hundred gallon Rubbermaid, but I hope to have my plywood build done soon then it may be undersized.

 

[Floyd R Turbo]

All plant life needs a dark period, so there is good reason for not doing 24/7. 22 would be the absolute max IMO.

Macroalgae "needs" a dark period? What evidence is there of that?

I lit my refugium for years 24/7. Macroalgae grew quite well. Then I switched to a day/night cycle and saw little change. Since the latter was cheaper, I went with it, but it is not so simple as they "need" it, IME.

I've known a few people who have run 24/7 and they grow a lot of algae, but most of them had better growth when they ran with a dark period of even a few hours. So maybe it's less of a need/requirement as it is results I've seen. The initial 18 on 6 off recommendation was made by SM so Randy if you think there is no basis for that, I'm not about to argue with you.

Other than that, I think that scrubbers are different from refugia in that you have less effects from shading and more utilization of incident light. Also each system is different, so what may work well for someone with a certain setup might result in no growth from too much light on another setup.