An acrylic algae turf scrubber.

[holmstar]

So, I've been having some trouble with nutrient build-up. No detectable levels of nitrate/phosphate, but there's plenty of visible micro algae in the display, so it's guaranteed to be there.

A month or two ago I started running GFO, and a few weeks ago modded my skimmer to recirculate/gravity feed from the overflow. On top of those I've been scraping and siphoning the algae out. I think it's making progress, but I'm still not happy, so I've decided to try an algae turf scrubber.


I looked at a few of the different designs out there and came up with this:

An old maxi jet pump provides the flow, and the lights are just 4 20watt soft white N.O. fluorescent bulbs. I read that warmer color temperature bulbs are better for growing algae, so that's why I went with soft white. I'd originally went with a 1/2 in fitting on the outlet, but it ended up being really noisy, as it would create a vortex and suck air into it. After taking the photo above I replaced that fitting with a 1 in fitting instead. It still pulls air down, but it's much much quieter.


I just built an acrylic box with flanges that extend out a bit to the sides, bonded the light sockets to the acrylic, and mounted the reflectors using some stainless machine screws.

The ballasts are mounted in a chamber on the bottom of the unit (open to the bottom for ventilation), protecting them from any drips.

On top I have a 1/2 in PVC pipe to which I've cut a 1/8th in slit. The PVC fittings are just slip-fit onto this pipe. The plastic mesh has small zip ties (not visible - they're currently inside the pipe) looped around the top, so that you can slide them into the pipe, and they are then too wide to fall through. The rubber o-ring is there to prevent water from dripping around the edge of the fitting and then down the side of the acrylic.

That's about it for now. It's been running since yesterday around noon, and I already see some small bits of turf algae that have gotten caught on the mesh. Now it needs to get growing! :thumbsup: I'll take a follow-up photo of the mesh next weekend. I imagine I should see some decent growth by then.

 

[nuccadoc]

Very nice! I would post this over in the Advanced section under the Algae Turf Scrubber Basics thread.

 

[holmstar]

Very nice! I would post this over in the Advanced section under the Algae Turf Scrubber Basics thread.

Cool, I added a link over there.

 

[wgood33]

Awesome design, simple and it is going to work. My story is similar, algae was growing but nothing was detectable in my water tests. I built my ATS in Aug 2010, it works great but here is a warning. Once you get a thick layer of turf, about 2 months, it is critical that you keep up on weekly prunings. If you don't keep up the turf will get very thick and lower levels of the turf will start producing nasties. I got hair algae and cyno by neglecting my maintenance, it took 2 months and 65 hermits to recover. Brown slime on the turf is what I saw when slacking off.
Are you running a sock or a carbon reactor? Bill :twitch:

 

[wgood33]

I would change the bulbs to warm white, cw is quite blue & you want browner. around 3000k color

 

[holmstar]

I would change the bulbs to warm white, cw is quite blue & you want browner. around 3000k color

They were listed as 3000k on the packaging. I forget what brand.

 

[holmstar]

Awesome design, simple and it is going to work. My story is similar, algae was growing but nothing was detectable in my water tests. I built my ATS in Aug 2010, it works great but here is a warning. Once you get a thick layer of turf, about 2 months, it is critical that you keep up on weekly prunings. If you don't keep up the turf will get very thick and lower levels of the turf will start producing nasties. I got hair algae and cyno by neglecting my maintenance, it took 2 months and 65 hermits to recover. Brown slime on the turf is what I saw when slacking off.
Are you running a sock or a carbon reactor? Bill :twitch:

Thanks for the advice! I'm running a BRS GFO/carbon reactor.

 

[Floyd R Turbo]

Nice looking enclosure!

I do see several red flags however, so I must comment. The biggest one is the placement of the ballasts. They should not be in contact with the acrylic, they really shouldn't be near it at all. They need to be remote from the box. I think you were going for the benefit of being able to move the box (for cleaning, repositioning, etc) without having to relocate or remove the ballasts maybe? I would try to find a quick-disconnect device instead and mount the ballasts remote from the box.

A hint: you need to place a cross-brace on both sides at the top, like an "I" beam, or else the box will warp outward over time, and it will stress your vertical seals. If you've been running it for a week, it probably has already started. Installing the braces may prove difficult, you may have to disconnect the scrubber and put the screen in the sump for a day while you clamp and brace the acrylic so that you can let the brace dry for 24 hrs (or more) without the sides trying to bow out and break the bond.

I'm guessing you went with the T12s because you had them already? Consider replacing with T5HO, you will get more light power from one 24W T5HO than you will from 2 20W T12s. It looks like you're running a 12" wide screen, so you're only using 1/2 of the length of the lamp as is.

What size tank are you running this on?

 

[holmstar]

Yeah they are barely warm now, but when ballasts fail, they can get VERY hot. I already have some water resistant quick connects, so this will probably be my first modification...

You may be right about the need for a top brace. It didn't really seem necessary since there is only an inch or so of water in it while running. It wouldn't be too hard to add them though. Hmm.

I went with T12 mainly because I'd seen examples of people getting decent results with regular spiral compacts with shop light reflectors, and figured that this would be a step up from that while remaining low cost. I didn't really want to spend the extra coin on a t5 setup if this would work. ...yeah I know 80w > 48w, so operating cost is a bit more, but that may be offset by cheaper bulbs.

[EDIT] After a few back of the napkin type calculations, it looks like the two T5 setup would be a few $ per year cheaper in terms of operating cost/bulb replacement, but the initial investment is about $100 more than T12. It would take quite a few years to earn back the investment, so I'm not disappointed with my choice.[/EDIT]

I actually have two sheets of mesh in there right now (with room for a bit more). When I took the photos there was only one.

This is on a 75 gallon display with another 75g sump.

 

[Floyd R Turbo]

It's not about saving money, it's about growing algae. You need 1 watt per gallon of T5HO or CFL (actual wattage) per gallon of water to grow algae at a high enough rate to uptake N and P appropriately. Your 80W of T12 = 44W of T5HO (adjusted correctly, a 20W T12 roughly equals 11 watts of T5HO) so your scrubber is about half power at best. It would fall into the 0.5 watt per gallon category, which is a minimal scrubber for a 75 gallon. This means that you would not want a large bio-load, and you would want to feed conservatively, and probably would want other filtration since this will not handle it stand-alone.

For full filtration, you would want at least 3x24W T5HO so you're probably going to want 2 on each side, or one and two worst case.

When it comes down to the cost, what you would probably want to look at is the cost of the additional T5HO lamps w/r to the savings of not having to run another type of filtration pump or buy replacement filtration media.

T12 is a step down from CFL, for scrubber purposes, properly reflected CFL is much better. T5HO is above CFL mainly because of linearity of the light source, which spreads out the intensity more evenly than CFL.

 

[holmstar]

Fair enough. I'll see how this goes. I wasn't ever planning to go skimmer-less anyway. I see it as more of a supplement to skimming than a replacement. Try to remove as much as possible with the skimmer, and control what the skimmer misses with an ATS.

 

[Floyd R Turbo]

Great! I just wanted to make sure you didn't miss something that would cause a problem down the line. I'll follow along and see how the system works out! Full tank shot??

 

[srusso]

How well is the maxi jet working for you? Remember you need 35gph per inch of screen width, I am going to take a wild guess and say your not getting that with your pump... I could be wrong though... Otherwise nice build... You did everything else great give that ATS a good pump! And your golden!

 

[holmstar]

Well, I'm getting flow over the entire length of the screen, but I don't know that it's 35gph at the head pressure of ~2ft or so.

On an unrelated note, In order to limit the possibility of "catastrophic combustion" I've gone ahead and moved the ballasts. They are now mounted on the wall sufficiently far from any source of water.

 

[misoldier06]

Not trying to nit pick you but something that i noticed were your screens looked brand new. They should be ruffed up as much as possible so that you can hardley see the light shining from the other side of the scrubber. If you leave it like this the algae will have a hard time holding on to the screen and could potentially fall off and flow back into your water column, where you DO NOT want it. The best way SantaMonica has said to ruff the screen up is to use a hole drill. Rub it all around the screen untill it becomes "cactus like". I promise it will help with growing algae. Good luck with the scrubber.

 

[holmstar]

Yep, I've read all that and seen the photos. The screens aren't quite as "new" as they look. I've scratched the heck out of them with a wire brush. My theory is that the algae needs rough features on a small scale more so than on a large scale. I could very well be wrong, but I'm the type of guy that likes to experiment, so I'm trying this first. I do have a set of hole saws that I can make use of if I'm not getting adhesion from the algae.

 

[wgood33]

You're gonna love the way this thing works. The screen prunings are a pain but it just takes way more nuisance algae out of the DT and the system runs cooler. I have not run a skimmer for 8 months!:dance:

 

[holmstar]

A hint: you need to place a cross-brace on both sides at the top, like an "I" beam, or else the box will warp outward over time, and it will stress your vertical seals. If you've been running it for a week, it probably has already started. Installing the braces may prove difficult, you may have to disconnect the scrubber and put the screen in the sump for a day while you clamp and brace the acrylic so that you can let the brace dry for 24 hrs (or more) without the sides trying to bow out and break the bond.

You may be right about the need for a top brace. It didn't really seem necessary since there is only an inch or so of water in it while running. It wouldn't be too hard to add them though. Hmm.

Turns out you were right Floyd. :thumbsup: The long vertical sections were beginning to bow outward, so I've added a couple of braces to the top. Still currently clamped, but the clamps should be ready to come off this afternoon.

 

[Floyd R Turbo]

Hopefully you caught it in time.

Regarding screen roughness, you are partially correct that algae needs small, rough areas to get a foothold. However, you need a cactus-rough screen as shown in my write-up on the scrubber basics thread (1035) because the weight of the algae needs to be supported once it starts growing thicker. So you might be OK, but if you start to see areas where algae has detached (empty spots on the screen) then you will know you need to rough it up more. You can rough-up an established screen without causing it to re-start, so no big worries.

I'm betting that your old maxi-jet is providing only minimal flow. But as long as you're getting flow across the whole screen and you're getting growth, and your N and P drop, you're accomplishing what you intended. Just be aware of the limitations of your scrubber when taking bio-load and feeding into account. Low flow and T12 NOs will contribute to slower growth rates and slower uptake of nutrients.

 

[holmstar]

It was pretty minimal bowing. I'm sure it'll be fine.

Regarding the screen, the "cactus like" texture is probably more likely to catch free algae, but I'm not convinced it's any better for algae adhesion. I'm not trying to knock other people's experience or anything. It's just my own theory, so I'm going to play around with it for a while.

I took a closer look at the pump, and it isn't actually a maxi-jet. It's rated for 350gph, about half of the unofficial guideline for my length not taking into account the head pressure. I'm not too concerned about it though. I'm going to let it run and see what happens.

And again, I'm not going for a skimmer replacement here in terms of efficiency. If it grows enough algae to keep it from growing in the display, then it's mission accomplished.