Turf scrubbers vs. other nutrient export

[DWIZUM]

Hello all,

I've been "turf scrubber curious" for a few years, and am likely going to include one on my next tank (roughly 250g, mixed reef.)

As I'm starting from scratch, instead of incorporating a scrubber on an existing tank as seems to be the case for many people on the forum, I'd like to plan ahead for how turf scrubbers mix (or don't) with other nutrient export methods. While I appreciate the concept that scrubbers will save your tank, mow the lawn, and do the dishes, I'd also like to build a robust and balanced system.

So, can people comment on using a scrubber along with skimmers, macroalgae in a refugium, carbon dosing, etc.?

Thanks in advance.

[jgreen1025]

Well, since none of the more knowledgeable people here have weighed in with their wisdom, I'll pass on my *thoughts* (which I often confuse with "wisdom"). Besides, I think this is an excellent topic for speculation.

My original tank was skimmerless and relied entirely on biological filtration provided by the sand and rock, with chaeto, halimaeda and xenia to provide some nutrient export (along with all the snails, worms and "pods" that thrived). The chaeto eventually died out for lack of nutrients but it worked fantastically in spite of what I considered a rather high load (50g tank with 3 chromis and 2 clowns) and heavy feeding. Hard and soft corals grew like crazy and I had little nuisance algae until work interferred and rudely took up too much of my time and energy (but it lasted about 3 years).

I'm now trying to recreate that earlier success but incorporating a turf screen as well - not only for nutrient reduction but also for production of all the little critters that serve as food and cleanup, etc. In addition, I'm hoping the whole system will be a friendly place for reproduction of herbivorous snails and other desireable animals and coral. I'm a little concerned that a screen could limit nutrients too well - I'm a fan of xenia, and I'd like to include more macro algaes this time - so I'm planning to experiment a little with the screen to manage this. But basically it'll all be natural filtration (I consider algae way more natural than a protein skimmer). The only things I plan to dose are calcium and alkalinity, and silica to encourage diatiom growth for snails (and hopefully sponges). Oh yeah, and phyto for filter feeders. Basically, I want a healthier and more natural tank, with not just fish and coral but all the other critters as well.

So, that's kind of my thoughts on turf scrubbers and what I'd like it to add to my system. I think it'll take a little effort to get it to that point, but that's half the fun, right?

[kcress]

I believe generally a turf scrubber will trump EVERYTHING else for export. So most anything else will die or fade away.

Of course you can always under size your screen or dial back its power to keep the nitrate levels at some point.

[SantaMonica]

The best way to lower the scrubbing power is via the lighting period: just reduce the hours. But by building a scrubber capable of full power, you can turn it back up when needed.

[jgreen1025]

I believe generally a turf scrubber will trump EVERYTHING else for export. So most anything else will die or fade away.


The best way to lower the scrubbing power is via the lighting period: just reduce the hours. But by building a scrubber capable of full power, you can turn it back up when needed.

That was kind of my thinking - that it could easily be too effective at reducing nutrients for my wants. It's still theoritical for now (I just got it up and running again last weekend, so there's no algae on the screen yet) but it's nice to know that cutting back on lighting is an easy option if it proves too much. I think my screen is 13"x10" (double-layered, and scratched up as much as I could) so it ought to be plenty big for my 50g tank, but we'll see how it goes.

Incidentally, I was at Home Depot last week getting another clamp light for it and the guy behind me asked if it was for a reptile. I said it was for a reef aquarium and he asked more about it so I told him it was for an "algae scrubber" - and he knew what it was! Unfortunately, I didn't have more time to talk right then, but maybe that shows what a good job Santa Monica has done in spreading the word.

[DWIZUM]

Thanks for the thoughts, everyone.


Basically, I want a healthier and more natural tank, with not just fish and coral but all the other critters as well.

That's what I want, too! Though perhaps slightly lower nutrients than your comments indicate.

My system is going to be 360g, and probably rather lightly stocked. Originally, it was going to be a basement sump (plenty of room) though now I'm leaning towards under-the-stand, which means much less space. My sump will have an 18" x 12" skimmer compartment, an 18" x 24" compartment, and an 18" x 12" return compartment. That middle 24" compartment will have about 20" of space above the water line. That's the area I've got to play with - for a refugium, scrubber, both, something else, etc. So now, I need to do some more research and get a design down.

It sounds like it would be futile to put a macroalgae-stocked refugium in that middle compartment if I'm using a scrubber there, but I'm still curious about balancing a scrubber vs. a skimmer. Has anyone run a very large mixed tank (with maybe a slight SPS focus, though not a twig tank) with ONLY a scrubber, or a scrubber and an undersized skimmer? Especially considering my space constraints?

The other possibility is to go back to a basement sump, but then pumping requirements go through the roof (I'm trying to keep power consumption reasonable.)

And speaking of power consumption, has anyone else thought about nutrient export per watt? Some of the needlewheel skimmers are extremely efficient in that you can heavily skim a big tank like this well under 100w. I understand that spiral compact fluorescent lamps are common for scrubbers, is anyone using anything else? LEDs, or even T5s? I'd imagine you could drop the power consumption by half or more compared to spiral compacts.

[SantaMonica]

has anyone else thought about nutrient export per watt?

Yes, and you need to remember that skimmers don't export ANY nutrients per watt. They export protein (food). So if you want to export the most food per watt, then get a good skimmer.

If you want to export nutrients (ammonia/ammonium, nitrite, nitrate, phosphate), then that's when you can start looking at scrubbers.

viewtopic.php?f=9&t=68 (http://www.algaescrubber.net/forums/viewtopic.php?f=9&t=68)



LEDs, or even T5s?

No, and yes.


I'd imagine you could drop the power consumption by half or more compared to spiral compacts.

No.

[DWIZUM]

Can you explain your last "no?"

Given the right component selection, LED lighting puts out more light (PAR, lumens, take your pick) than any other type of lighting, and you can pretty much pick the exact spectrum you want by blending different color emitters. Hence I would assume that, given an ideal light profile (i.e. name your intensity, spectrum, etc.) LED would be the best choice, no matter the criteria. Meanwhile, spiral compact fluorescent lamps use inefficient built-in drivers, and by the very nature of their spiral design, there's a ton of light wasted thanks to restrike and the basic omnidirectional nature of the light output. Even T5 should be better (in terms of light that reaches the algae vs watts consumed) because you can use a good reflector design and more efficient ballasts.

Other than the mantra of "use spiral compact" is there any information available regarding the "best" intensity, spectrum, etc. of light for this turf algae to grow?

I've read plenty of success stories for scrubbers, but also plenty of "falure" stories. It's not always clear what separates the two, since often the techniques will seem similar. Hence, I have some questions about things that I'm wondering might separate the successes from the failures, beyond the typical things discussed.

I'm interested in knowing what typically limits algae growth in a system with a large scrubber and no other nutrient export. Are people seeing N and P sucked down to zero, or does one typically linger while the other is zero? This is assuming you've got the right light and flow I suppose. If you had the right light and flow, and N and P were both detectable in the tank, then I guess you'd have to look at defficiencies of some other nutrient.

I spent a lot of time measuring and adjusting levels of various nutrients in planted freshwater tanks when those were my focus, how similar are marine turf algaes to typical FW plants in terms of nutrient needs? Have there ever been efforts to supplement nutrients proven to be limiting growth in a scrubbed tank?

And what about a carbon source? Again, referencing planted FW tanks, it was very common to supplement CO2. Has anyone ever monitored O2 or CO2 levels in a scrubbed tank?

[DWIZUM]

has anyone else thought about nutrient export per watt?

Yes, and you need to remember that skimmers don't export ANY nutrients per watt.

So, if not skimming, what forms of nutrient export did you compare it to in terms of export capability per watt consumed?

[jgreen1025]

And what about a carbon source? Again, referencing planted FW tanks, it was very common to supplement CO2. Has anyone ever monitored O2 or CO2 levels in a scrubbed tank?

This article might be helpful: Photosynthesis and the Reef Aquarium, Part I: Carbon Sources by Randy Holmes-Farley (http://reefkeeping.com/issues/2006-10/rhf/index.php) where he discusses CO2 in reef tanks. (As far as chemistry issues go, Randy is THE Expert, in my opinion).

I think you said you haven't yet set up a scrubber but you have a reef tank you could try one with? Scrubbers are pretty simple and inexpensive to build, and what you learn might help in your planning for the 250g reef.

[DWIZUM]

Thanks for the link. I'm a big fan of Randy but somehow missed that article.

Here's a silly question I haven't seen answered anywhere. What the scientific name for the specie(s) of algae that typically grow on these scrubbers?

[DWIZUM]

I think you said you haven't yet set up a scrubber but you have a reef tank you could try one with? Scrubbers are pretty simple and inexpensive to build, and what you learn might help in your planning for the 250g reef.

Sadly no - I've moved twice in the last year and have taken down all of my "serious" tanks, so I'll basically be building this 360g system as a first scrubbed system. That said, I tend to take things slowly and don't expect it to be fully stocked for two or three years, so I'll have plenty of time to experiment.

[jgreen1025]

Taking it slow is always wise regardless of the method used. As for the species of algae I think it depends on what's existing in your system. If you manage to grow true "turf" algae it might be a variety, but maybe it's a little more standard if it just grows the regular green hair algae. I found this quote by Eric Borneman (another reliable "Expert" in my opinion):


Eric Borneman Posted 5/14/2007 (http://forum.marinedepot.com/FindPost67756.aspx)
If you build it, they will come. If you want, you can scavenge little patches of various turfs from others, stores, etc. Inland Aquatics used to (and perhaps still does) seed their screens with a lot of species, and these went through successions. Mine currently remains dominated by Derbesia though I did seed some patches of a red astro-turf like species. It got outcompeted. Be careful, though. Some of the turfs that are on maricultured fragments, for example, are really invasive, and if you got those in the main tank, you might not be too happy. They are definitely not just intertidal hair algae. So, my advice is probably just let it happen.

My current screen has been running for just over a week now (prior screens have suffered from being unplugged by the cleaning lady and drying out, and a burned out pump... it's a long story) and it's got brown diatoms and a bit of green hair algae. Once it's working and the main tank is algae-free again I'll re-seed the sandbed - I use the mud and gunk from the bottom of the LFS live rock tanks (it's probably not a method many would dare to try, but it's always worked spectacularly for me). It will be interesting to see if that makes any difference in the algae that grows on the screen.

[DWIZUM]

Interesting. I'm asking about species because (especially given that article you posted) there's at least some information out there about how different species react to different conditions.

A question for those both successful and unsuccessful with scrubbers: Do you have any hard evidence to show what limits algae growth? Since we're using the algae as a tool to get unwanted nutrients out of the tank, I'd assume we would want to do whatever it takes to make sure it is those very nutrients that are limiting growth. Which means we'd want to play with lighting, flow, carbon sources, other nutrients that may not be available in the right proportions, etc.

[schnitm]

I recently added a second screen. Didn't exactly "need" it but I have a phosphate problem and while GFO is working very well...I can't help but tinker.

The second screen is identical in design to the first with one exception. Identical screen, identical lights (even replaced all the bulbs when I put it in), idetical plumbing, but... The first has about 35 GPH of flow per inch. The new screen has approximately 50 GPH per inch. This is a lot of flow and I'm having problems keeping it all attached.

The result after two weeks? The new screen is starving out the old one. The old screen is getting pale spots and was relatively thin at harvest on Sunday. I scraped more off the new screen (only two weeks old!) and it's a uniform forest green.

[kcress]

Nice test schnitm! So to repeat,, the higher flow is winning?

[DWIZUM]

The first has about 35 GPH of flow per inch. The new screen has approximately 50 GPH per inch. This is a lot of flow and I'm having problems keeping it all attached.

Did you actually get the flow totally attached though? Comparing these "sheet style" scrubbers to the old-school surge-style scrubbers, I'm wondering what role aeration plays in growth rates. In other words, is the faster flow important because it aids in aeration, or just because faster is somehow otherwise better?

[SantaMonica]

Can you explain your last "no?"

Algae growth is a function of light-power, i.e., wattage. You need the same wattage, CFL or LED, to grow properly. Using a low-wattage LED will grow nothing.

T5's are better because all parts of the bulb are near the screen.


Other than the mantra of "use spiral compact" is there any information available regarding the "best" intensity, spectrum, etc. of light for this turf algae to grow?

See the FAQ; that's was is currently known.


I've read plenty of success stories for scrubbers, but also plenty of "falure" stories. It's not always clear what separates the two, since often the techniques will seem similar.

It's clear to me. There has always been a glaring problem in the build/operation, that is, if they report it on my threads. If they don't, many times they can't figure it out.


I'm interested in knowing what typically limits algae growth in a system with a large scrubber and no other nutrient export. Are people seeing N and P sucked down to zero, or does one typically linger while the other is zero?

They both go down to unmeasureable values. Then growth slows. For us, it does not matter if it's N or P.


If you had the right light and flow, and N and P were both detectable in the tank, then I guess you'd have to look at defficiencies of some other nutrient.

No, then you have to look at an improperly built/operated scrubber.


how similar are marine turf algaes to typical FW plants in terms of nutrient needs?

I don't know. But I do know that FW and SW algae both fight for N and P.


Have there ever been efforts to supplement nutrients proven to be limiting growth in a scrubbed tank?

Minimal efforts. My opinion is that any limited scrubber growth is always due to build/operation. That's how every single situation works out.


Has anyone ever monitored O2 or CO2 levels in a scrubbed tank?

O2 is always high. But no monitored efforts as far as I know.


So, if not skimming, what forms of nutrient export did you compare it to in terms of export capability per watt consumed?

Everything else but skimming. Really, it's in the FAQ.


What the scientific name for the specie(s) of algae that typically grow on these scrubbers?

Don't know.


If you manage to grow true "turf" algae it might be a variety, but maybe it's a little more standard if it just grows the regular green hair algae.

Eric calls all scrubber algae "turf". But the type of turf that most folks are referring to requires a surge, and thus is not recommended as it is too difficult.


there's at least some information out there about how different species react to different conditions.

Yes but you have no control over what grows.


Do you have any hard evidence to show what limits algae growth?

Yes: Hundreds of scrubbers with clumps of algae that fell off into the system (from a non-rough screen). This truly is the limiting factor for most people.

We are a long way from needing to chemically tweak these systems; the biggest improvements are from just following the hardly-ever-followed guidelines.


The old screen is getting pale spots and was relatively thin at harvest on Sunday.

This is, as mentioned, probably clumps that fell off.


I scraped more off the new screen (only two weeks old!) and it's a uniform forest green.

Because it had a solid sheet of plastic to attach to, whereas the old one was spotted with dead roots which let go.


the higher flow is winning?

The more-attachable plastic is winning.


I'm wondering what role aeration plays in growth rates.

Nothing; air is not required.

[schnitm]

Hmmm...

Some algae is falling off the old screen but not much. 95% of what was there on the uncleaned side Sunday is still there. It's loosing it's color. Some almost looks white. I have not had attachment problems, although I think I have had the nutrient associated problems described in SM's last thesis.

The flow is different, but another variable may be the root of this. The "new" screen may have arrived at an opportunistic moment. This system had very high nutrient levels at the start followed by undetectable nitrates but high phosphates. Just before installing the new screen I droped the phosphates to undetectable with GFO. I am begining to suspect a species change is happening on the "old" screen. That screen developed in a high phosphate environment and the phosphates are now very low.

I'm going to leave things as they are and see what develops. Will also try to take pictures.

[DWIZUM]

SantaMonica,

Let me preface this post by stating that I'm not looking for an argument, or trying to disprove or cast doubt on your methods (which clearly work). Rather, I'm trying to understand the reasons why they work, so I can have the best chance at success. The way I do that is by asking questions. Hopefully that doesn't come across the wrong way. :)



Can you explain your last "no?"

Algae growth is a function of light-power, i.e., wattage. You need the same wattage, CFL or LED, to grow properly. Using a low-wattage LED will grow nothing.


I'm not sure about this assumption. A watt is a measure of electrical energy. A watt spent powering an LED does not produce the same results (in terms of light energy) as a watt spent powering fluorescent or metal halide. Photosynthetic organisms don't know or care how many watts are consumed by your lighting device, they care how much light energy you're producing. Hence, I would assume that if a particular LED fixture is producing X amount of PAR (or lumens, or lux - pick your favorite) in a certain spectrum, and a fluorescent fixture was producing the same color and amount of light, they'd have the same result in terms of growth on the scrubber.

However, you can certainly produce a certain amount of light energy more efficiently with LEDs, since they are capable of producing more light energy per unit of electricity consumed. I spend way more time than humanly reasonable thinking about and experimenting with lighting technologies over conventional reef tanks and planted FW tanks, so I know this is true in the general sense, even though I've never built a scrubber powered by LED. If someone has built a low-wattage HB LED scrubber and it has failed, I'd like to talk to them, to see what brand, model, bin, spectrum, etc. of LEDs they were using.

This is also why I'm interested in knowing the intensity and spectrum of lighting that works best on scrubbers. If 2700k CFLs seem to be the clear winners, then duplicating the same intensity and spectrum of light with LEDs should allow us to build scrubbers that are cheaper to operate in the long term (less electricity cost and no lamps to change every few months.)



I've read plenty of success stories for scrubbers, but also plenty of "falure" stories. It's not always clear what separates the two, since often the techniques will seem similar.

It's clear to me. There has always been a glaring problem in the build/operation, that is, if they report it on my threads. If they don't, many times they can't figure it out.
[/quote:ijmxrlbq]

Again, I apologize for my lack of insight - I've read the FAQs and nearly every build thread on these and other forums, but I'm still failing to see a pattern. If you were to summarize into a few bullet points the most common modes of failure, what would they be?


[quote:ijmxrlbq]the higher flow is winning?

The more-attachable plastic is winning.[/quote:ijmxrlbq]

Does a certain flow rate play a role in success or failure?


[quote:ijmxrlbq]I'm wondering what role aeration plays in growth rates.

Nothing; air is not required.[/quote:ijmxrlbq]

Now I'm confused. I thought aeration was the whole reason these scrubbers were constructed the way they were (sheets suspended in mid air with a thin layer of water flowing over them, or the old surge-style where the sheet was exposed to air for several seconds/minutes at a time.) If aeration plays no role, why not just put the sheet underwater in a conventional sump and use a powerhead or natural flow through the sump to provide water movement?

Thanks again for taking the time to answer my questions.

[schnitm]

The flow across the surface of a vertical ATS is VERY fast. It is a very thinn sheet of FAST moving water. Very hard to achieve that in the water. The size of pump required to achieve that flow rate at the algae-water interface would have to be huge!

It is my impression that my algae has very little contact with air. It is encased in the sheets of rapidly flowing water. The bubbles that appear are from photosynthesis not a direct interaction with room air. When a spot may be directly interacting with air, it's at a low flow spot and it doesn't grow well. I think as you go away from the vertical model the necessary flow is difficult to maintain and other methods, like surge, might work better.

[DWIZUM]

The flow across the surface of a vertical ATS is VERY fast. It is a very thinn sheet of FAST moving water.

Ok, but wasn't SM just commenting that rate of flow isn't important?

[SantaMonica]

Some almost looks white.

They they are not getting enough flow.


That screen developed in a high phosphate environment and the phosphates are now very low.

Clean it off completely then. You don't want any high-nutrient dark stuff remaining.


However, you can certainly produce a certain amount of light energy more efficiently with LEDs

You can experiment if you want, but don't use LED's if you need results. I know all of what you are saying, but it doesn't matter. LED's have not worked, yet, and thus cannot be recommended.


If you were to summarize into a few bullet points the most common modes of failure, what would they be?

Slick screen
Not cleaning
Weak light
Weak flow
Too small


Does a certain flow rate play a role in success or failure?

If the screen is not rough, high flow will knock algae off.


I thought aeration was the whole reason these scrubbers were constructed the way they were (sheets suspended in mid air with a thin layer of water flowing over them, or the old surge-style where the sheet was exposed to air for several seconds/minutes at a time.)

Nope.


If aeration plays no role, why not just put the sheet underwater in a conventional sump and use a powerhead or natural flow through the sump to provide water movement?

Boundary layer:
viewtopic.php?f=9&t=286 (http://www.algaescrubber.net/forums/viewtopic.php?f=9&t=286)

[kcress]

Have you paged thru my build?
viewtopic.php?f=3&t=98 (http://www.algaescrubber.net/forums/viewtopic.php?f=3&t=98)

There I show two different LED panels. The first one was ineffective. The second was effective. my feeling is a little more power would have been useful but I'm not sure, as with projects like this variables are being changed a little too often.

Certainly the photonic rate is all that the algae cares about. (And the spectrum)

If I were to build another LED light it would certainly be HPLEDs not gum drops again. It turns out that you can get far more light out of far less expensive LEDs by using HPLEDs. You do have to deal with the spreading issue as you generally want the LEDs fairly close to the screen because who wants a 3 foot wide scrubber? Application of some clear diamond diffuser plate would probably be desirable.


As for aeration it seems that it is unimportant. The hair algae is the type that grows underwater. It extracts and respires into water. Exposing it to the air does not do anything to help it in that regard. If you are talking about 'classic turf' found beach side, then that is less clear. If you are using a bucket dumping style TS and you are cultivating that kind of turf, then perhaps air contact would be desirable. I will say that 'classic' turf I've grown did very well continuously submerged.

I suspect that air contact still has minimal or no effect with a flood/drain system. The real benefit of a the F/D system is the defeat of boundary conditions. Water jetting past a mat of HA down the front of a screen results in virtually no flow right up against the algae. So under a few layers almost nothing is happening. With a F/D there is much more new water contact with all of the turf because all they water drains off then is replaced cyclically.

Of course F/D results in discontinuous clank, woosh, clank woosh, noises which may be an issue with 95% of the setups.