Algae Scrubber Basics

[Floyd R Turbo]

Read that article closely. It only works at very low power so I'm thinking it will be more like decades before this becomes a end-user reality.

 

[cdivine]

Sorry if this has been covered before, but I have a question on removing the screen for cleaning. I have seen people using Unions to remove the PVC and then I guess they clean the screen with it still attached to the PVC. Is this the best/easiest way to design it?

 

[Floyd R Turbo]

You will want to take the screen out of the slot and clean the slot and the top edge of the screen, hence the use of zip ties or beaded ties (which I prefer)

 

[Dwerbs]

So, I have finally got my apex set up and I have the scrubber lights on 18 off 6. And ever since I started that my algae has turned that dark brown that so many people seem to be having trouble with. Should I increase my light time?

 

[Floyd R Turbo]

If you were getting good growth with 24 hr lighting and now it's 18/6 and it's not good, that is not necessarily a cause and effect relationship. I explain this below, hope it helps.

If you're running 18 on 6 off and not getting proper growth, then something else is missing. A picture would help because that is the best way to tell what is going on. I went back in the thread and saw your posts and it looked pretty green and healthy at 2/18, then you followed that post with a statement that it looked pretty yellow. So I'm a little confused.

From your posts: your screen is 6" wide x 10" tall and 2 x 23W CFL floodlights, 400 GPH, 3 pinches of NLS 1mmm pellets/day.

For reference, 0.1 oz or 2.8g of pellet food is roughly equal to 1 cube. This would mean you would be going through a 150g jar of NLS every 2 months. If you measured this out on a scale, I'm betting that 0.1 oz would be on the order of 1/2-3/4 teaspoon but that's out of thin air.

Your screen is 60 sq in which is enough for 5 cubes/day, if it was fully lit. You have 46W of CFL Floodlight on it which is not quite as efficient as a top-end reflector, so I would say that is probably closer to an equivalent of 35-40W let's say. That means that what you really have is about a 3 cube/day scrubber.

Based on that, you could feed up to 0.3 oz or 8.4 g/day of pellet food, in which case you would be tearing through food at the breakneck rate of one 150g jar every 18 days. If you are not doing this, then your screen is still oversized / underfed. This leads to your algae trying to spread out and grow across a larger area, which means more algae competing for the same amount of nutrients (waste), and it turns a yellowish color. The difference between yellow and brown is kind of hard to describe. To one person the yellow algae might look brown, and might photograph darker or lighter as well.

Yellow algae is kind of squishy and rubbery, almost gel like in a way, and is a sign of too much light in relation to the available nutrients (more on this later).

Brown algae is the other direction, too much nutrients, and that's one step from the oily black stuff. Brown is not gooey or anything, it's more of a slime or turfy type of algae. You can also get a brown slime on top of the yellow rubbery stuff too (this is what I see right now) so don't confuse that for brown growth, because it's not.

If you concentrate the growing area down to the proper area for what you are feeding and that algae no longer has to compete for space to grow, it is forced to grow in the space with the best available light and flow.

I think what could be happening here is that your screen is (still) a little large, and/or you're feeding is not lined up with the screen capacity. You may benefit from blocking the light to the top section of the screen, and concentrating the light toward the bottom. This would 'cut off' the top part of the screen from growing excess algae in an area where it gets lower light anyways.

Like many what you are seeing is that when you first run a scrubber, it pulls out all the stuff that other filtration systems didn't, and you get bushy green growth so you think "great, done it right!" Then over time, the system is cleaned up and the scrubber only has the input of food into the tank to pull out, and it is now oversized. This can happen at varying degrees of time and speed of the shift over, depending on the established time of the system, previous filtration, condition of live rock, etc. Also screen growth can vary from week to week with nothing changing, but the long-term trend is what you need to pay attention to. This shift from green to brown/yellow growth usually happens over the course of a month or two. This is why pictures help, so post them if you can.

Also I think you're plumbed to the overflow so you're kind of set on the flow rate, but 66 GPH/in is a little high, even with a very rough screen (and I think your is rough enough) it could tend to tear away growth. But it's not high on my list of things I would change.

 

[Dwerbs]

Wow, thanks Floyd. Ya when it was first set up it was very green around the edges and very thick very light green in the centre(focal point of the lights) As for food I am doing probably a teaspoon of 1mm NLS pellets twice a day, maybe a little more. Plus a cube of frozen every couple days. I am thinking I am more on the slimy brown side of things but I will take a picture tonight for you to look at once I am home.
The reasoning behind the 6x10 is with my current setup I can't really lower it any lower so it needs to be 10 long so it is in the water, stop a alot of splashing.

 

[jimrawr]

What's the deal with black slimy growth?? That's what I am getting now but I don't have high no3 or po4.

 

[RexBrown]

I had seen SantaMonica mention that there would be a new design that doesn't require a pipe with the slot in it. Any word on when we can see it? I'm curious to know if I can modify my design to match the new upcoming specs.

 

[Heavy Hittah]

Rex you'll have to wait til april

 

[Floyd R Turbo]

What's the deal with black slimy growth?? That's what I am getting now but I don't have high no3 or po4.

It's an indicator of high nutrients or not enough light. could be somehtng else too. Specs on your system (tank and scrubber) and pics would help

 

[jimrawr]

My system is a 92g corner with a 20g sump. I feed one cube per day, and then a couple pinches of flakes, and also about a 2x2" piece of nori. I forget the flow of the scrubber, but I had calculated it back when I was setting it up and its was according to specs. The flow isnt really even, I am getting a lot more on one side than the other. Going to try and fix that next time I clean the screen. Bulbs are 23w CFL, and are on a 12/12 cycle right now. More than that and the screen was burning.

Last time I tested PO4 = .04 and NO3 = < 1

Here are a couple pics

last time I cleaned it

 

[Floyd R Turbo]

Jim, your screen is grealy oversized for what you feed. From counting the holes, I'm guessing it's about 5 x 12 = 60 sq in which is good for 5 cubes/day. 2 x 23w = 46W so it's a little under lit as well.

I can also see a yello layer under the brown layer. This is algae that is dying because the light is being blocked, and it probably has a kind of putrid smell when you are cleaning it as well (that's dead roots)

The burning does not appear to be related to distance from the screen, it is probably related to the screen being oversized. The algae is trying to grow across a larger area than the water has nutrients (waste) to support for green growth. Your test results indicate it is doing a good job of pulling waste out of the water so that is good.

Less time with more intense light is better than more time with weaker light. Decreasing an already weak lighting setup will make the situation worse, what you need to do at a minimum is increase the wattage and then lower the photoperiod (and you may need to back the lights off a bit if you do that option)

This setup might have produced a good harvest of green algae for a while I'm guessing. That's because it's pulling waste out of the water and rocks that has built up over time. That phase, if you had it, is over. Now it's just pulling out what you feed.

Based on your feeding, you only need 24 sq in at the most. That would be only 4" tall for your setup.

Since you're space limited and already have the flow right and need to provide a path to the top of the sump, I would think your best option would be to trim the screen down to about 6" long and then attach another section of smooth screen to that with small zip ties, and switch your lamps to 23W CFL floodlights, which are good for about 5-6" wide. Focus those only on the lower 4" of that 6" tall screen. CFL floodlights are good for focusing all of the light in a concentrated area. The intensity is knocked down a bit by the (typically) frosted glass, so you may be able to put them a little closer, and you may be able to run them shorter than 18 hours.

The CFL floodlight and smaller screen would be my first option. You can use the same fixtures, just remove the reflectors. Second option would be to up the CFLs to around 30W and back off the distance and time as needed. I don't like the second option as much because you're still left with an oversized screen, and without feeding 4x more you're just going to continue to get yellow rubbery with a dark slime coating. This is actually what I am getting after a year+ of scrubbing on an established tank and as result I am 1) learning still and 2) rebuilding the scrubber.

 

[jimrawr]

Jim, your screen is grealy oversized for what you feed. From counting the holes, I'm guessing it's about 5 x 12 = 60 sq in which is good for 5 cubes/day. 2 x 23w = 46W so it's a little under lit as well.

I can also see a yello layer under the brown layer. This is algae that is dying because the light is being blocked, and it probably has a kind of putrid smell when you are cleaning it as well (that's dead roots)

The burning does not appear to be related to distance from the screen, it is probably related to the screen being oversized. The algae is trying to grow across a larger area than the water has nutrients (waste) to support for green growth. Your test results indicate it is doing a good job of pulling waste out of the water so that is good.

Less time with more intense light is better than more time with weaker light. Decreasing an already weak lighting setup will make the situation worse, what you need to do at a minimum is increase the wattage and then lower the photoperiod (and you may need to back the lights off a bit if you do that option)

This setup might have produced a good harvest of green algae for a while I'm guessing. That's because it's pulling waste out of the water and rocks that has built up over time. That phase, if you had it, is over. Now it's just pulling out what you feed.

Based on your feeding, you only need 24 sq in at the most. That would be only 4" tall for your setup.

Since you're space limited and already have the flow right and need to provide a path to the top of the sump, I would think your best option would be to trim the screen down to about 6" long and then attach another section of smooth screen to that with small zip ties, and switch your lamps to 23W CFL floodlights, which are good for about 5-6" wide. Focus those only on the lower 4" of that 6" tall screen. CFL floodlights are good for focusing all of the light in a concentrated area. The intensity is knocked down a bit by the (typically) frosted glass, so you may be able to put them a little closer, and you may be able to run them shorter than 18 hours.

The CFL floodlight and smaller screen would be my first option. You can use the same fixtures, just remove the reflectors. Second option would be to up the CFLs to around 30W and back off the distance and time as needed. I don't like the second option as much because you're still left with an oversized screen, and without feeding 4x more you're just going to continue to get yellow rubbery with a dark slime coating. This is actually what I am getting after a year+ of scrubbing on an established tank and as result I am 1) learning still and 2) rebuilding the scrubber.

Yea, the screen is 6x11". I had bigger (I think they were 43w?) bulbs on it before but it would burn the middle of the screen. I was never able to harvest good green growth. I also never had super high nutrient, PO4 was never above .08 and NO3 never tested above 2ppm. So maybe thats why it never got great growth?

What you say about my room limitations is spot on. This is why my scrubber is oversized, it needs to be 11" long or it wont hit the water and there will be a lot of splashing and noise. What you suggested makes sense to me, but maybe its better if I start out with a new screen? Only rough up 6 inches at the top and leave the rest smooth.

I will try that out, remove the reflectors and change the bulbs to flood lights and see if that helps. Thanks for the length and informative post!!

 

[Floyd R Turbo]

Yea, the screen is 6x11". I had bigger (I think they were 43w?) bulbs on it before but it would burn the middle of the screen. I was never able to harvest good green growth. I also never had super high nutrient, PO4 was never above .08 and NO3 never tested above 2ppm. So maybe thats why it never got great growth?

What you say about my room limitations is spot on. This is why my scrubber is oversized, it needs to be 11" long or it wont hit the water and there will be a lot of splashing and noise. What you suggested makes sense to me, but maybe its better if I start out with a new screen? Only rough up 6 inches at the top and leave the rest smooth.

I will try that out, remove the reflectors and change the bulbs to flood lights and see if that helps. Thanks for the length and informative post!!

Yes, If your tank was never overfed, overrun with algae, or had high N or P, then you probably did start out too big and that would explain things.

If you're going to make a new screen, leave the top 1.5-2" smooth, rough up a 4" tall section (use some blue painters tape to make yourself a "window") and then leave the bottom 5-6" smooth for the transition down to the sump. Then focus the lights on the roughed-up area only (using CFL floodlights).

You can accomplish the same thing by just cutting down the screen you have and attaching a new section of screen though. If your screen is rough where it is inserted into the slot that's not the best, but it's not the end of the world either. You will just need to scrub that down with a stiff brush during each screen cleaning. You could attach a new section to the top and the bottom also. Just find the tiny zip ties, should work OK, but you might get some unwanted stray water at the junction of the smooth-to-rough screen at the top, which would tend to bounce out towards your lights. CFL floods are easier to clean but who wants to clean their lamps all the time ya know?

Either way you do it, you will still end up with some growth on the smooth section, and it will probably be kind of slimy like the brown slime coating you have now, and will wash off very easily when you clean, so you'll want to scrub that smooth area with an old (clean) toothbrush too.

 

[Floyd R Turbo]

This was posted on another site and I felt it was worth sharing. It is an alternative to the slotted pipe (he admits it's "experimental") and also an expansion on the saran wrap idea - quite a good one also.

I've been unhappy with the slot design on my scrubber. It's always been a bit finicky and prone to getting growth up in it. After I switched to Herbie style drains, that meant that it would throw off the balance of the drains and send water down the backup drains as the algae grew. I tried several light blocking schemes, but they didn't seem to fix the problem. Since the slot would get gummed up after a week or so, I could never let the scrubber really grow to the "3D" stage.

The current solution to the problem, which I have only run now for two weeks, so it is still "experimental", does away with the slot altogether. To hang the screen, I made a "loop" of plastic canvas, and stitched that to the top of the screen with braided fishing line. The screen then hangs from the pipe by the loop, and the pipe just slides into the loop. No need for zip ties or curtain rings to hold a screen in a slot. For flow, I drilled a 3/16" hole every 1/2" along the pipe. The holes point down. The water flows out of the holes into the area where the loop joins the screen, then through the holes in the plastic canvas loop and down either side of the screen. The flow is very even along the screen.

For reference, the scrubber box is roughly 20" long by 10" high. I added an extension to the box so the pipe actually sits up above the box by an inch. The pipe is 3/4", about 20" long. Flow comes in from both ends. Roughly 800-900 gph of total flow. There are two screens, each roughly 10" by 10". The scrubber is LED lit. See one of my other threads for details on the LEDs.

Have a look at the pictures. Maybe that will help my explanation...

I did get some spray where the loop joined the screen, since the pipe sits above the box, that would have killed the solution, but then something Floyd mentioned in one of his posts caught my attention... Saranwrap. I laid a piece of Saranwrap over the loop and stopped the spray immediately. The drag created by the flow pulls the plastic wrap right down to the screen, but it doesn't stop the flow, it just evens it out a bit. Then, I wondered if a piece of thin plastic from a black plastic garbage bag would do the job, since it would also be a great light blocker as well. I tried it and it worked like a charm.

I'm extremely pleased with how the new setup is working-- no spray, no growth into the slot messing up the flow, perfectly even flow across the screen. I let it go for two weeks and just about filled up the box with algae.

If you are having trouble with the slot-- cutting it, getting it the right width, keeping it clean, etc., give some thought to trying this system. Even if you stick with the slot, try the garbage bag light blocker, I think you'll be pleased with what it does for evening the flow.


Pic1-- screen hanging from the pipe by the loop
Pic2-- the pipe with the holes
Pic3-- screen hanging in the box
Pic4-- with the black plastic as a spray guard

Note on the screen on the left side in Pic2-- this is a new screen, but I stitched pieces of an old screen to it to seed it. I'll let it run this way for another couple weeks, then take the old pieces off.

 

[Floyd R Turbo]

The only add-on I have for this is that some kind of step should be taken to keep the black plastic (or saran wrap for that matter) in place no matter what. Something dislodging that piece of material, say after a power outage where it dried out or something like that, would be a total disaster. I follow Murphy's Law when it comes to these things!!

 

[jimrawr]

I made the modifications to my screen. I have two inches at the top that are scrubbed as clean as possible, 4x6" area where I hope to grow green algae, and then the screen is cut and ziptied to another clean screen. Only thing I didnt change was the lighting yet, going to see how it works out before getting new bulbs.

Also, part of the algae was yellow and looked dead (like you had noticed as well), so I tried to totally clean that off the screen completely with a brush. Was I correct in doing that?

 

[Floyd R Turbo]

I try to clean the areas that don't grow green a little better than areas that do, but I don't scrub it hard down to the bare screen. I think I may have once and it didn't seem to make a difference, so no harm done. It might take a few cycles to start growing green again, but less time than a brand new screen.

See how it goes. Might be worth changing one side to CFL floods and look for differences after a few weeks.

 

[jwoyshnar]

Any of you guys go skimmer less since going to an algae scrubber?

 

[Floyd R Turbo]

I didn't really have a choice due to the way the system was set up, I pulled filter socks and skimmer when I put the scrubber on back on 10/10/10. Since then I have only run a 100mL bag of purigen (for 6 months, then pulled the whole tank due to a fracture), occasionally ran carbon but not for long, and that's about it.