Algae Scrubber Advanced

[ali1]

With all the diy vertical scrubbers out there, what shortcuts/tips/accessories do you use that helped maintenance/cleaning so simple. Im finding it a pain to clean my scrubber every 10days.

 

[SantaMonica]

More harvest mass = more filtering. That's what you want. If you don't mind less filtering, just let it go more days; roots will die and start letting go, putting some nutrients back into the water which will appear to you as less filtering. But it will still filter.

 

[ali1]

So i now have a scrubber thats 20x14... pretty wide and i grow algae like crazy. I have the below lights on each side of my scrubber and the edges of the scrubber isnt growing. If i move the lights further away, will that help spread? Or do i need to buy more lights to cover the sides. Im already 100watts per side.


https://www.amazon.com/gp/aw/d/B017...dpPl=1&dpID=51LNqqqbBdL&ref=plSrch&th=1&psc=1

 

[Scrubber_steve]

So i now have a scrubber thats 20x14... pretty wide and i grow algae like crazy. I have the below lights on each side of my scrubber and the edges of the scrubber isnt growing. If i move the lights further away, will that help spread? Or do i need to buy more lights to cover the sides. Im already 100watts per side.


https://www.amazon.com/gp/aw/d/B017...dpPl=1&dpID=51LNqqqbBdL&ref=plSrch&th=1&psc=1

If your present growth is controlling NO3 & PO4 levels I wouldn't worry about no growth on the edges.
With that type of light fixture you'll never get complete & even growth on the screen, without wasting light, unless the screen is cut to the shape of the beam angles of the light fixture.
Moving the lights further away from the screen will increase in area of coverage, but the intensity will reduce, of course. You shouldn't need to move it too much though to increase the spread so its worth trying before adding another light.

 

[karimwassef]

If it's working, don't worry about it. Moving it back a little won't change the spread much since those LEDs are directional (no lenses) and the metal around it is a secondary reflector.

I use those lights too.

 

[ali1]

Thanks RC team! Nitrates/phosphate levels are 0 so im happy

 

[ali1]

Below is my scrubber results. Always had dark green turf . Now Im getting shades of light green and dark green. Concerns?

 

[Floyd R Turbo]

Not really, what's likely happening is that your water chemistry is changing a bit. Usually, as your nutrients drop, or as the rate of nutrient delivery drops, from a higher level where you're getting dark growth to a lower level, the growth will start to get lighter and usually more volumous. That's assuming you haven't changed anything else. At this point I would not worry, but I would keep an eye on it for any other changes.

Just so all the bases are covered, a few questions:

Screen dims?
Light type/description?
Photoperiod?
Tank Size?
Feeding?
Livestock?

 

[SantaMonica]

shades of light green and dark green

Flow is getting cut off in the lighter green areas.

 

[Scrubber_steve]

so, with a waterfall scrubber all the specifications have been well constrained in regards to screen sizes needed and light intensity & flow over the screen.

But what specs are their for tank turnover rates - the number of times the volume of water in a tank needs to go through a scrubber per hour to effectively control inorganic nitrogen & phosphate build-up over a 24 hour period?

You can have two tanks with very different volumes, but with the same fish populations, using the same size scrubber. Is 0.5 x tank turnover per hour enough? Or is a 3 x tank turnover per hour a minimum?

Seems this aspect has been neglected as I've never seen any information covering it.

 

[Scrubber_steve]

Continuing along with this Tank Turnover Rate paradox, & something that directly affects this.

I don't believe that increasing the rate of flow over the screen of a down flow scrubber, above the minimum
required to completely immerse the algae and stop water channelling, will increase the fraction of inorganics
removed by the algae with each tank turnover.
The algae can only remove a fraction of the inorganics available in the water passing over it, and I can't see
any reason why a faster flow should change the value of this fraction.

In regards to the important water - air interface created by the thin layer of water flowing down over the algae
in a downflow scrubber, a quicker flow would increase the thickness of the layer.

Perhaps I'm wrong?

 

[SantaMonica]

You are right, extra waterfall flow does not help that much. And sump turnover is almost irrelevant.

What's most important is an air/water turbulent interface, which faster downfalling water can help with. But this can be outweighed by detaching slime from the screen.

 

[Floyd R Turbo]

@Twinfallz, you're right and wrong

Excess flow does not seem to benefit much, unless you have the ability to sort of "inject" it into the mat rather than just allowing it to flow over the top. Even then, IMO, it's a marginal improvement

Too little flow can mean slower flow through a larger/thicker algae mat and incremental increases in flow would likely benefit to a certain point.

So there is a point of diminishing returns with relation to flow volume (more accurately, speed)

But I think a focus on a "tank turnover rate" is not a primary concern, but rather something that you just might consider when choosing or designing a scrubber. On a larger tank, a wider scrubber means higher overall flow.

Taken to an extreme, a narrow and very tall scrubber would mean a long pass, lowering the nutrients more on a single pass. But, you have a lower TTR. The result with that scenario compared to a screen with the same area but 4x wider means less contact time but more TTR, so the result over the long term is pretty much the same.

The net effect is that it's pretty much a wash.

Combine that along with lower flow rates in general being relatively effective, TTR is even less of a factor. What I mean by that is that the 35 GPH/in "rule of thumb" IMO is really not a target anymore, it's good to get close to that, but you can still run a quite effective scrubber with a lot less flow. Hitting 35 GPH/in is not going to make or break your scrubber. I've seen examples of great growth with something like 20-25 GPH/in. IMO that 35 GPH/in rule is reduced to a target maximum but not a hard & fast rule by any means.

 

[Scrubber_steve]

You are right, extra waterfall flow does not help that much. And sump turnover is almost irrelevant.

What's most important is an air/water turbulent interface, which faster downfalling water can help with. But this can be outweighed by detaching slime from the screen.

I always like to consider how paticular scenarios affect a healthy mature screen, and ignore new and immature screen particulars as a new screen won't be new for long after all.

What the minimum flow rate over any particular mature screen with algae growing on it is, I don't know. It may vary from one screen to the next, but only slightly I'd imagine.
And you can go above that rate whatever it happens to be.
But a reasonably constrained figure for minimum flow rate should be identified because an effective TTR would be based on that figure.

I think TTR is important because, if a fraction of the available inorganics are taken up with each tank turnover through a scrubber then the turnover needs to occur enough times during a 24 hour period to remove 100% of the inorganics in the aquariums water.
Otherwise there'll be a deficit and inorganics will accumulate.

 

[Scrubber_steve]

@Twinfallz, you're right and wrong
But I think a focus on a "tank turnover rate" is not a primary concern, but rather something that you just might consider when choosing or designing a scrubber. On a larger tank, a wider scrubber means higher overall flow.

Yes & no.

Two tanks, both 800 litres, both fed 2 cubes per day.

Tank #1 uses a 2 cube 6" screen scrubber with a flow over rate of 800 L/hour, which = TTR of 24 per 24 hours

Tank #2 uses a 2 cube 12" screen scrubber with a flow over rate of 1,600 L/hour which = TTR of 48 per 24 hours

The filtering capacity of scrubber #2 is theoretically twice that of scrubber #1 because Tank #2 has twice the TTR per 24 hours, and achieved this without increasing the speed of flow over the screen.

 

[Floyd R Turbo]

You're missing the fact that if they are both 2 cube/day screens, then they have the same LxW area.

Tank #1 screen with a 6" wide screen would have to be 4" tall = 24 sq in
Tank #2 screen with a 12" wide screen would have to be 2" tall = 24 sq in

Tank #1's screen would receive 1/2 the total flow, but each pass makes contact with 4" of vertical algae growth substrate.

Tank #2's screen gets 2x the [total] flow of #1 but each pass makes contact with only 2" of vertical algae growth substrate.

All other things being equal, those 2 scenarios are nearly identical.

[edited]

 

[Scrubber_steve]

You're missing the fact that if they are both 2 cube/day screens, then they have the same LxW area.

[edited]

No, not missing this fact; it's actually the point I'm making.

Look at this way.

A fraction of the aquarium' inorganics are filtered from it's water each time its volume passes through the scrubber.

So if you have a tank turnover twice an hour through the scrubber it will remove twice the fraction of inorganics that is does with only one tank turnover through the scrubber per hour.

Now on tank #1 if we double the turnover, we will have to do it by doubling the speed of flow over the screen, and I think we agree that doing this will not increase the fraction of inorganics removed from the water.
You can double or tripple the flow through the scrubber, and as a consuquence, double or tripple the TTR, but if increasing the speed of flow through the scrubber doesn't increase the fraction of inorganics taken out of the water, it will make no difference.

But if we double the width of the screen without doubling the surface area, and we double the flow over the screen without increasing the speed of flow we do increase the fraction of inorganics removed.

 

[Scrubber_steve]

You're missing the fact that if they are both 2 cube/day screens, then they have the same LxW area.
[edited]

Apologies Bud, you're right I'm wrong!

Widening the screen without increasing its surface area doesn't increase the filtering, it just means you need a bigger pump. LOL

what if you doubled the flow over Tank #1 screen, would this increased nutrient uptake over a 24 hour period?

What got me think about this TTR thing is that a scrubber removes a fraction of the available nutrients with each tank turnover through the scrubber. So you need multiple tank turnovers every 24 hours to remove 100% of the nutrients or you get rising nutrients.

We don't know the value of the fraction removed, so you cannot calculate the number of tank turnovers needed.

How was the cube equivalent - screen size calculated without knowing these imputs?

was it a guess that just worked ???

 

[Floyd R Turbo]

The cube equivalent was developed by Bryan / Santa Monica, basically from what I understand he took 2 of his SM100 scrubbers and put them on a 90g tank and then fed liquid coral food according to his developed cube-equivalent measurement method, and then basically fed the equivalent of about 22 cubes/day for a length of time, then figured that this feeding rate was about the maximum that those 2 scrubbers could handle.

Then he did total screen LxW area divided by cubes/day and came up with 12 sq in per cube of food per day.

IMO that one has stood pretty solid as a rule of thumb. There are ways to make a certain size screen more efficient by designing to encourage 3D growth

 

[Scrubber_steve]

Then he did total screen LxW area divided by cubes/day and came up with 12 sq in per cube of food per day.



There are ways to make a certain size screen more efficient by designing to encourage 3D growth

Interesting; thanks

What are these ways & what is 3D growth exactly