Algae Scrubber Basics

[Floyd R Turbo]

A waterfall version can pack in algae just as well as a UAS so this is not totally unique. The UAS and waterfall are on opposite ends of the spectrum on the water flow issue.

One end is to have very low water flow and have the water make multiple passes across the media, resulting in the effluent water being "highly polished".

The other end is to have the water pass in high volume, the result being that each pass filters a lesser amount.

The net result, theoretically, should be the same. Think about it mathematically. Both filtration methods on comparable systems. Let's say 100g.

System "A" takes 1 gallon and filters it 80% per pass, at a rate of 100 GPH
In 1 hour: 1 gallon x 100gal/hr x 80% = 80 gallons filtered. 80% effective.

System "B" takes 1 gallon and filters it 5% per pass, at a rate of 1600 GPH
In 1 hour: 1 gallon x 1600 gal/hr x 5% = 80 gallons filtered. 80% effective.

This is vastly simplified just for an example and does not imply that an UAS is 80% effective nor that a waterfall is 5%.

You could get a similar effect on a waterfall scrubber setup in a sump by reducing the sump-tank turnover rate and putting the scrubber feed pump near the return end (near the tank return pump) and the scrubber effluent near the drain (from the tank) essentially creating a recirculating path.

You could also compare the UAS in this example to a denitrator in that a denitrator uses very low flow but performs a high rate of water purification (for nitrate, anyways)

So in theory, high-flow + multiple passes should be on par with low-flow + recirculating.

It's just another way to skin the cat.


Addtionally: while I agree that water passing over the top of an algae mass basically does nothing, I disagree with a blanket statement that seems to imply that a higher flow rate on a waterfall screen does nothing - because I've seen the results of increasing the flow over a mature waterfall screen and it definitely makes a difference in growth rate, and in the right setup, a big difference.

 

[herring_fish]

That's why upflow versions with strong bubbles can pack with algae when there is only small holes to allow for water flow.

Are you saying that air can find its way into little holes in a mat once it has formed? I don't want them to form at all.

Additionally: while I agree that water passing over the top of an algae mass basically does nothing, I disagree with a blanket statement that seems to imply that a higher flow rate on a waterfall screen does nothing - because I've seen the results of increasing the flow over a mature waterfall screen and it definitely makes a difference in growth rate, and in the right setup, a big difference.

The game show host said, "œAnd the studies SLOW? " Higher flow, within certain limits is very beneficial. Many many studies show this to be true.

As for air flow: Again, all this has been studied and water caries off nutrients not air! When I originally proposed this in 09, I understood that air can create flow and some turbulence but the bottom line is water contact. That is why I proposed if for limited applications only.

That is also why I continued to actually use my old scrubber after posting the design, because it is better that air injection. More water gets to the cell walls and the boundary layers are degraded more completely. Without surge, a good impeller pump can be better than an air drive.

On the other hand, there is one notable benefit of air contact and that benefit is called marketing.

 

[Floyd R Turbo]

SM: That's why upflow versions with strong bubbles can pack with algae when there is only small holes to allow for water flow.

Are you saying that air can find its way into little holes in a mat once it has formed? I don’t want them to form at all.

I think he was referring to the hole(s) in the bottom side of the HOG/SURF that allow water to enter the growth chamber

...Higher flow, within certain limits is very beneficial. Many many studies show this to be true.

...water caries off nutrients not air! When I originally proposed this in 09, I understood that air can create flow and some turbulence but the bottom line is water contact...

That is also why I continued to actually use my old scrubber after posting the design, because it is better that air injection. More water gets to the cell walls and the boundary layers are degraded more completely. Without surge, a good impeller pump can be better than an air drive.

Remember though,

the enclosed growth compartment increases the dwell time of the water and bubbles inside the unit so that they rub the algae many times before leaving the compartment. This actually reduces nutrients (nitrate, phosphate) to a level lower than the outside water, which allows greener growth to occur sooner (lower nutrients grows greener algae) inside the unit, especially in high-nutrient aquarium water. In other words, the [UAS] creates a lower-nutrient ecosystem inside itself which is different from the rest of the water in your aquarium

^^ this is the claim for the floating style UAS but could just as easily apply to the vertical enclosed style "when there is only small holes to allow for water flow"

Not that I disagree with you HF...just trying to rile you up :headwalls: :ape:

On the other hand, there is one notable benefit of air contact and that benefit is called marketing.

Snap!

 

[herring_fish]

Smile,
I think that I agrea with you. LOL

 

[thejuggernaut]

I think the main benefit of air is the fact that its cheap and easy to setup. Plumbing in a vertical style scrubber requires more setup, where as with one of the air driven ones, you just clamp it on the sump walls and plug it in. Even if there is a small loss in efficiency it is probably worth it to allot of people just for the ease of setup and the small footprint of the devise.

I searched the term air/water interface and I can't many references to it. Are you saying that algae processes better when it has a boundary layer of fast moving water and air? I saw what was said about the water not moving fast, and in the area of the entire devise you maybe right, but as far as the immediate vicinity of the algae strands, that water is agitating pretty dang quick when you pump a ton of air around it.

 

[Floyd R Turbo]

Yes, the bubbles do create a lot of rapid and localize motion when they pass, which breaks the boundary layer so this definitely causes nutrient exchange. If that wasn't the case, you wouldn't grow much algae.

You are correct that the UAS is cheap and easy to build, that is it's advantage.

As for the loss in efficiency, this is really the unknown factor. IMO, any significant difference in efficiency is likely to be a result of water turnover rate. I would like to see some experiments myself, on all types of scrubbers, to settle this issue, or at least shed light on it. Myself and at least one other have been throwing around ideas about how to do this, so it's only a matter of time before we actually take it on.

 

[thejuggernaut]

So dumb idea, but how about an upflow scrubber that uses a water pump to pump water up and out of the top of a housing. If bubbles are required just use a skimmer pump. Possibly best of both worlds. Got an old sicce psk-2500 laying around?

 

[Floyd R Turbo]

My first UAS an enclosed box sitting in top of the tank, lit from both sides, pump fed from the top, air bar in the bottom, etc. basically, what you says. It grows algae but can't handle a high bioload. I've ran this scrubber since pretty much day 1 of the reveal of the UAS, made dozens of adjustments, and it has been nothing short of disappointing

 

[thejuggernaut]

Well I've learned enough to start building me one. I'm going to build a waterfall style scrubber with some LEDs and see how it works.

 

[Floyd R Turbo]

Here's a pretty good example. This is from an enclosed-box waterfall scrubber, 660nm Deep Red LEDs (plus a few blues), 2" on center, running at 350mA (break-in/maturing stage), 2" from the screen, 8.5 hr/day photoperiod, growth at 30 days from scratch

 

[Rybren]

I recently built myself a HOG SM style UAS. Yes, I know that it won't be as efficient or effective as a waterfall style, but it fits in well with the cramped space in my sump area. My hope is that this scrubber will supplement my existing filtration. I have no plans to remove my skimmer, GFO/GAC reactor, lit fuge, or stand-alone cryptic fuge.

The screen size is ~ 5x8 and is a combination of #7 screen (that has been in my sump for a few years) and plastic chicken wire (the same stuff that I used for my tank cover) I added the chicken wire because I use some of it as a nori feeder and found that algae likes to grow on it - and quickly.

For bubbles, I'm using a flexible wand type bubbler. It does make small bubbles, but it generates a lot of flow.

I've ordered 10 660nm LEDs, but they haven't arrived yet. I'm not sure how many I should use. As an interim measure, it is being lit by 2 x 6500k and 1 x Royal Blue 3W LEDs that I had kicking around. I'm running 12hrs on for now.

It's been running for 10 days now and there is a noticeable brown growth on the screens. I was thinking of waiting until the 14 day mark before the first cleaning.

Sorry, I don't have any pics.

 

[Floyd R Turbo]

10 on one side of a 5x8 screen is good. You could also do 5 on a side if you had the ability to light both sides.

Give it time to mature, submerged UASs using plastic canvas sometimes take quite a while to mature, and the algae dies not anchor strongly to it.

 

[Rybren]

Thanks for the tips.

 

[thejuggernaut]

My first UAS an enclosed box sitting in top of the tank, lit from both sides, pump fed from the top, air bar in the bottom, etc. basically, what you says. It grows algae but can't handle a high bioload. I've ran this scrubber since pretty much day 1 of the reveal of the UAS, made dozens of adjustments, and it has been nothing short of disappointing

Do you have any photos of this setup?

So what do you think is the problem with this design?

 

[SantaMonica]

Are you saying that air can find its way into little holes in a mat once it has formed? I don’t want them to form at all.

No I was not saying that, but in a floating upflow, the upflowing bubbles do open up pathways for light to shine down.

I think the main benefit of air is the fact that its cheap and easy to setup

This too, and also pod survival.

Are you saying that algae processes better when it has a boundary layer of fast moving water and air?

Yes. Or more accurately, faster moving water reduces the thickness of the boundary layer.

a noticeable brown growth on the screens

Scrub this off; green hair cannot attach to slime.

 

[Crispy001]

Are there some texts/articles/white papers covering algae scrubbers you guys would recommend? I'd really like to learn more about the research and development of scrubbers; while this thread is great, I feel the information is too scattered for my purposes. Any links or recommendations for books would be greatly appreciated!

 

[mrbncal]

cool

cool

Here's a pretty good example. This is from an enclosed-box waterfall scrubber, 660nm Deep Red LEDs (plus a few blues), 2" on center, running at 350mA (break-in/maturing stage), 2" from the screen, 8.5 hr/day photoperiod, growth at 30 days from scratch

Any more info on this scrubber build? I like the black cover idea and would like to see more on this.

 

[DavidinGA]

So...

I'm running an established ats, skimmer, chaeto, and now pretty deep into vodka dosing. 240 gal total volume and 20ish fish (ten are medium sized tangs).

I'm starting to get more spongy yellow growth on my screen now as my nutrients drop from the carbon dosing that is still increasing (up to 12ml a day of vodka now).

For the time being I want to continue to use the ats but since my nutrients are going down and I don't want to increase feedings should I simply begin to reduce the lighting time period on the ats to maintain healthy green growth or what?

 

[SantaMonica]

Just needs more iron. Dose Kent's Iron+Manganese, or feed a lot more nori.

 

[Mental1]

I have set up my ATS, it's in a 35 gallon tank all by itself, how long do I wait to determine if I did a good or bad job and need to modify? It's been running since Sunday, but made some changes last night. Should I see any signs of algae yet? Because I'm not so I can make more modifications ...