Algae Scrubber Basics

[Floyd R Turbo]

The feeding guideline was introduced by SM about 6 months prior to the unveiling of his UAS concept, but essentially was arrived at I believe due to the anecdotal evidence that supported it.

Since then he (recently) has backtracked and made up a new guideline based on tank conditions and the whole "phosphate leeching" theory but my opinion is that this, like any guideline, does not hold true for all devices and conditions.

If you build one optimally, I can tell you that the 12 sqin/cube/day guideline is pretty good. You can double the size (and lighting) and still get good growth/filtration, but beyond that your growth tends to thin out.

One factor is lighting. Up until around the time of the feeding guideline, LED wasn't really "solid". Now it is on more solid ground, but there are still limits to be found. I've found that initially you need a much lower level of LED light for the maturing stage (too much actually slows the process) but then after you have an established screen you can increase light intensity and photoperiod in concert with flow rate and you end up with a wide range of filtration capacity. So if you start out with 9hrs/day at 1/2 power, then after maturing you can bump up the length of the photoperiod with the same flow and extend the filtration time. When you hit an upper limit on time or your growth starts to be too "dense" (but green) then you can increase the intensity and back off the photoperiod. Now you have an option to further extend the photoperiod should the shorter but more intense cycle still not cut it.

The bottom line is that the guideline is meant to get you in the ballpark, and in most cases, it takes care of things pretty well. IMO the "tank conditions" guideline is not written for or appropriate for waterfall scrubbers. There really needs to be 2 guidelines because waterfall and UAS devices are inherently very different in forum, function, and results.

 

[DavidinGA]

The feeding guideline was introduced by SM about 6 months prior to the unveiling of his UAS concept, but essentially was arrived at I believe due to the anecdotal evidence that supported it.

Since then he (recently) has backtracked and made up a new guideline based on tank conditions and the whole "phosphate leeching" theory but my opinion is that this, like any guideline, does not hold true for all devices and conditions.

If you build one optimally, I can tell you that the 12 sqin/cube/day guideline is pretty good. You can double the size (and lighting) and still get good growth/filtration, but beyond that your growth tends to thin out.

One factor is lighting. Up until around the time of the feeding guideline, LED wasn't really "solid". Now it is on more solid ground, but there are still limits to be found. I've found that initially you need a much lower level of LED light for the maturing stage (too much actually slows the process) but then after you have an established screen you can increase light intensity and photoperiod in concert with flow rate and you end up with a wide range of filtration capacity. So if you start out with 9hrs/day at 1/2 power, then after maturing you can bump up the length of the photoperiod with the same flow and extend the filtration time. When you hit an upper limit on time or your growth starts to be too "dense" (but green) then you can increase the intensity and back off the photoperiod. Now you have an option to further extend the photoperiod should the shorter but more intense cycle still not cut it.

The bottom line is that the guideline is meant to get you in the ballpark, and in most cases, it takes care of things pretty well. IMO the "tank conditions" guideline is not written for or appropriate for waterfall scrubbers. There really needs to be 2 guidelines because waterfall and UAS devices are inherently very different in forum, function, and results.

So.... Should I oversize the screen a bit?

 

[Floyd R Turbo]

It probably won't hurt to go as high as 2x over what you feed. Sometimes it just gets difficult to construct/install as it gets bigger. There is a bit of "diminishing returns" effect as you go larger. So a screen that is 2.0x what you feed might not be 33% more effective than a screen that is 1.5x what you feed.

Also another factor that seems to come back into play with larger tanks is screen width, because as you increase width (at the same flow rate per inch of slot) you increase the overall tank turnover rate.

Taken to the extreme, a 10x6 screen that is 10" wide at 35 GPH/in = 350 GPH total flow. Same screen except 6" wide 10" tall is 6x35=210GPH total flow. NOt much of a factor in smaller tanks. This is where the old "tank volume" guideline starts to creep back into the equation as a secondary factor. Meaning that you might want to start with dims for what you feed, then extend the screen width wise from that to increase turnover rate. Make sense?

 

[DavidinGA]

It probably won't hurt to go as high as 2x over what you feed. Sometimes it just gets difficult to construct/install as it gets bigger. There is a bit of "diminishing returns" effect as you go larger. So a screen that is 2.0x what you feed might not be 33% more effective than a screen that is 1.5x what you feed.

Also another factor that seems to come back into play with larger tanks is screen width, because as you increase width (at the same flow rate per inch of slot) you increase the overall tank turnover rate.

Taken to the extreme, a 10x6 screen that is 10" wide at 35 GPH/in = 350 GPH total flow. Same screen except 6" wide 10" tall is 6x35=210GPH total flow. NOt much of a factor in smaller tanks. This is where the old "tank volume" guideline starts to creep back into the equation as a secondary factor. Meaning that you might want to start with dims for what you feed, then extend the screen width wise from that to increase turnover rate. Make sense?

Right.

I was thinking if I stayed with the feed value sizing that I would do a short sized screen (maybe 6-7in wide) that is longer so I could get away with a smaller/cheaper pump (a screen only 6in wide requires a much weaker/cheaper pump than if i make the screen 10in wide). Your saying that is actually going to be counter productive? I should do a wider screen?

 

[treyman]

hello everyone.

looking for some quick help. I've had my DIY algae scrubber up and running for about 5 days now, with literally no algae growth. heres a few photos of my set up from yesterday.

im using a pump that i found lying around. its very strong, and i wish i could tell you brand and model, but cant. all i know is it seems like it is overkill, so i restricted flow via a valve.

the bulbs im using are CFL Spots (Utilitech 15-Watt (65W) BR30 Medium Base Soft White (2,700K)) purchased in a 2 pack from lowes. I have one on each side pointed right at the center of the screen.

the only conclusion i can come to as to why i have no growth is due to the light bulbs im using? any guidance someone could provide would be great.

also, my nitrates are registering in the 80 ppm to 160 ppm range tested via the API test kit.

my tank is 100 gal, with roughly 50 lb to 75 lbs of live rock, again dont know the exact. one small clown fish, no corals, a couple shrimp and a couple small crabs.

my ultimate goal is to get coral ready, but to do so i want this ATS to be functioning properly. and i dont want to add anything live to the tank until i get everything under control.

-T

 

[Floyd R Turbo]

Not necessarily counter productive, I wouldn't go that far. Just mildly less effective. You can still increase flow to get higher turnover, but with a DIY open screen, more flow means more chance of sideways spray. There is a solution for that also though.

 

[Floyd R Turbo]

up and running for about 5 days now, with literally no algae growth

5 days isn't that long - you need to give it time. At least a few weeks

the bulbs im using are CFL Spots (Utilitech 15-Watt (65W) BR30 Medium Base Soft White (2,700K))

Those look right, but these are good for about a 6x6 area, so you will not get much growth on extremities of the screen. I would keep these for now and just let the screen get started, and add more lights if need later.

also, my nitrates are registering in the 80 ppm to 160 ppm range tested via the API test kit.

I've ran into issue trying to get a bare screen started on a very high nutrient tank. The issue is the conundrum. GHA grows best in lower-nutrient conditions. But you need good growth to get to lower nutrient conditions, and GHA seems to filter best.

What happened to me was that I ended up getting a thin, sheet-like growth (kind of like Nori) that peeled off in strips easily...and it didn't seem to grow fast, or make a dent in nutrients.

What usually happens in high-nutrient tanks + CFL lighting is you get black growth on the screen. It looks thin and oily and blocks nearly all the light to the screen, so you have to remove it regularly with a brush.

In cases like yours, what you really need to do is a couple of big PWCs to get the "starting point" nutrient level down to a reasonable level. Let the scrubber get started up, and take the nutrients down from there.

 

[treyman]

got it, will give that a try and update in a week or so if still no luck.

thanks!

 

[DavidinGA]

Not necessarily counter productive, I wouldn't go that far. Just mildly less effective. You can still increase flow to get higher turnover, but with a DIY open screen, more flow means more chance of sideways spray. There is a solution for that also though.

I should have added that I am and will continue to run my skimmer and gfo (as needed probably as I have been: use it for 30days then stop for 30 days). This would probably mean I also don't need as large of a screen, right?


As I understand it a scrubber does not take up silicates, right? If not, that was my primary reason for still running some gfo.

 

[SantaMonica]

Correct, no silicates. But silicates probably won't be a concern once N and P are low.

 

[Triggerfish]

Here are pictures of my setup, its a single pump

I got that same lamp shade.. ha

 

[DavidinGA]

Is this the right screen?

I got it at Walmart and the brand is Darice craft designer but it doesn't say number 7...

 

[Brummie]

Dunno, being English. Not a clue what that coin is. 7 per inch is good

 

[Floyd R Turbo]

#7 is 7 holes/inch. That looks like the right stuff.
#5=5 holes/inch
#10=10 holes/inch

 

[DavidinGA]

#7 is 7 holes/inch. That looks like the right stuff.
#5=5 holes/inch
#10=10 holes/inch

K thanks

 

[DavidinGA]

Seems to me that the biggest "problem" in making a scrubber is actually the easiest!

If you have a miter saw (compound/sliding miter saw for longer pipes) it's super super super easy to get a perfect straight proper sized slot. Fwiw it would have been a HUGE pain to do this by hand with any other hand held tool.

I just clamped in some 2x4s to create a non-moving form to keep the pipe perfectly in place.

Easy.

 

[Floyd R Turbo]

Yep, that is one way to do it. The thing you have to remember is that most blades are 1/10" not 1/8". 1/40 of an inch may not seem like much but this actually makes a difference when your screen is 1/16" thick and the slot needs to be 1/8" wide, leaving 1/32" of clearance on each side. Using a 1/10" wide blade leaves you now 1/64" clearance for water passage, which increases backpressure (head) and you are left with lower overall flow than if you used an extra-wide blade.

I had to by a $60 Bosch blade to get a 1/8" wide cut.

Also Schedule 40 pipe is thinner and will pinch in the middle, so when you make your cut and still have it secured in place, cut it a second time to trim it out. S40 pipe will also close/pinch in the middle over time, so the longer the slot the more it will pinch closed.

Better yet, use Schedule 80 pipe. Same thing, double-cut it. It won't pinch as much initially or over time, and is not much more expensive.

 

[DavidinGA]

Yep, that is one way to do it. The thing you have to remember is that most blades are 1/10" not 1/8". 1/40 of an inch may not seem like much but this actually makes a difference when your screen is 1/16" thick and the slot needs to be 1/8" wide, leaving 1/32" of clearance on each side. Using a 1/10" wide blade leaves you now 1/64" clearance for water passage, which increases backpressure (head) and you are left with lower overall flow than if you used an extra-wide blade.

I had to by a $60 Bosch blade to get a 1/8" wide cut.

Also Schedule 40 pipe is thinner and will pinch in the middle, so when you make your cut and still have it secured in place, cut it a second time to trim it out. S40 pipe will also close/pinch in the middle over time, so the longer the slot the more it will pinch closed.

Better yet, use Schedule 80 pipe. Same thing, double-cut it. It won't pinch as much initially or over time, and is not much more expensive.

K. Good to know.

To my eye on the tape measure it appeared to cut 1/8. Might be need to double check it.

I'm going to run a pump that I was planning to dial back because it's too powerful, so perhaps I'll run it stronger if my slot is too narrow to combat that...?

My slot is 12" long and my pump is a rio 2100 running 3/4" clear tubing from the pump to the 3/4in pvc. The scrubber will only be approximately 12 inches above the pump.

At 0 head the pump does 692gph, 1 head 666, 2 head 600, 3 head 486. So even if I somehow lost 3 head I'm still 66gph over what I need (on paper tho I'm sure the real world gph numbers are different).

 

[Floyd R Turbo]

If you have a calipers, measure the width of the teeth as well as the slot.

With that pump in the setup, your flow should be fine, but the other issue with a slot that is a bit too narrow is that as you get growth at the slot, it can tend to spray sideways and if you have more pressure due to the narrower slot, these 'streamers' as I call them can be more of a concern. Having something to block the light to the slot/screen junction becomes a bit more important.

 

[DavidinGA]

If you have a calipers, measure the width of the teeth as well as the slot.

With that pump in the setup, your flow should be fine, but the other issue with a slot that is a bit too narrow is that as you get growth at the slot, it can tend to spray sideways and if you have more pressure due to the narrower slot, these 'streamers' as I call them can be more of a concern. Having something to block the light to the slot/screen junction becomes a bit more important.

I don't have calipers but looking for a standard reference for thickness/width a us nickel is 1/16 of an inch thick so 2 nickels is an 1/8" thick.

When I get home I'll have to see if two nickels fit...