My first attempt

[worley]

The setup:
My first attempt was a wooden frame that sits over the top of a sump (which is located in our loft/attic, with water pumped up through the walls/ceiling via a peristaltic pump).
It was lined with thin clear plastic to protect the wood, with 4 outdoor, waterproof bulkheads holding a 15w spiral compact fluroescent bulb in each. The bulkheads with the bulbs in are mounted on top of the plastic, about 1" away from the mesh on each side.
The 1200lph pump pumps water up to the PVC pipe with the plastic mesh (9" wide, 18" long).

The problems:
The normal household 15W spiral compact fluroescent bulbs are:

a) too dull
b) too bulky to make a nice compact filter
c) too low colour temperature


I'm having a lot of problems trying to get the mesh to not splash water, I've had two attempts at cutting the PVC pipe, the second attempt worked better, but cutting with a dremel seems to melt the plastic behind the cutting wheel and end up with a slightly wonky cut. The other issue is that when cut, the PVC pipe seems to push the center of the line that's cut together and almost look like you've not cut it at all, or that it's being compressed, like a spring almost, probably the way the plastic is made.


Some new ideas:
Well, I've started a new design.
The lights:
I've got 4 Philips PL-L fitting, 18W 6500K bulbs, with ballasts that control two bulbs each.
The "pros":
a) For only 18W, they are amazingly bright
b) they are a "cool daylight" 6500k colour temp, likely to grow algae a lot better
c) much more compact, about 1/3 of the depth of the spiral/energy saving bulbs
Cons:
a) Require a seperate ballast
b) Cost very little (around £3.50/$6 per bulb), however the ballasts cost a fair bit (£16/$27) each

The new design I'm working on, will have a similar wooden frame, with plastic inside, but have the lights behind the plastic, with mirrors behind them to double the output of the lights, this will make the width of the filter much much smaller as the plastic on the inside of the frame can be 1" away from the frame from either side, and only need to be 1" wide on either side of that to contain the lights and mirrors.
I'll post some photos as I get along with it this weekend.
Tom.

[Marshs]

I'll be putting one together for my 2.5 gallon Pico Reef.

I will be pulling the water out of the back of my AquaClear-70 HOB filter using a powerhead.
It will flow up a 11" tube and then down over the (one sided) screen (turf algae filter) and back down into the HOB.
With this small of a tank, I'll only need a small screen 8" tall by 3.5" wide. Once I get this done and working, I'll be ordering my Red/Brown Algae screen from Mike at Inland Aquatics (812) 232-9000.

Once I have some pictures - I'll put them on here.

Have a great day and don't forget to upload some photos.

Thanks,
Steve

[SantaMonica]

Tom yours seems a special setup. Pics would help.

I talked with Steve on the phone today; he'll be modifying his build a bit. But it will be applicable to the thousands of nano/hob users out there.

[worley]

Yeah, I'll post some pics later.
I'm trying to get a very slimline design with maximum light and the bulbs as close as possible to the mesh.

[worley]

Here's some photos of the setup:
The plumbing (2x 6mm RO unit pipes through the side of the sump acting as an overflow, with a 6l/h peristaltic pump sucking water up into the loft/attic into the sump)
[attachment=8:3ffiym3l]TOM_3632.jpg[/attachment:3ffiym3l]

Attempt/Design 1:
[attachment=7:3ffiym3l]TOM_3639.jpg[/attachment:3ffiym3l]
The problem with this one was the lights just didn't produce enough light (4x 15W compact fluroescent, roughly 3000k colour temp).
Also the water splashed everywher (as you can see!), even shorted out the IP44 rated bulkhead at one point :shock:
So I took it apart and put new plastic over the wood, sillicon sealed it in, and put 4x 18W PL-L 6500k bulbs in:
[attachment=6:3ffiym3l]TOM_3658.jpg[/attachment:3ffiym3l]

Notice how thin the unit is now, with the lights contained within the width of the wooden baton:
[attachment=5:3ffiym3l]TOM_3666.jpg[/attachment:3ffiym3l]

With a mirror behind the unit, there is a huge improvement in light compared to the old design:
[attachment=4:3ffiym3l]TOM_3664.jpg[/attachment:3ffiym3l]

Sitting in place on the sump in the attic (notice the peristaltic pump on the left), with the mesh in place:
[attachment=3:3ffiym3l]TOM_3667.jpg[/attachment:3ffiym3l]
[attachment=2:3ffiym3l]TOM_3669.jpg[/attachment:3ffiym3l]
[attachment=1:3ffiym3l]TOM_3670.jpg[/attachment:3ffiym3l]
[attachment=0:3ffiym3l]TOM_3672.jpg[/attachment:3ffiym3l]
Notice now, after a few tips from the guys on cutting the pipe, there's no splashing (the only water on the plastic is from when the mesh was taken out).
The distance from the mesh to the light on either side is around 2.5", and with a mirror, it's about 4.5" away from the reflection of the other side of the bulb.
Total lighting power: 72W @ 6500k

[SantaMonica]

Now that's some construction :)

72W might be fine; my T5HO's are only 96W.

[worley]

:D sure is, I would have preferred to do it all in acryllic, but it costs a fortune over here in the UK (£40/sq m or $6/sq ft), even for pretty thin sheets. If I shopped around a bit I guess I may be able to find it a bit cheaper, but not really worked with it before, so wooden frame just seemed much faster to prototype :lol:

[worley]

First issue...
Came downstairs this morning to find about 4litres (roughly 1 gal) of salt water on the floor dripping from the ceiling where the algae scrubber is located in the loft...
What had happened was the mesh had come loose at one side and fallen under it's own weight, and was half hanging out and water had splashed everywhere, luckily it was a fairly small amount of water (had some spare RO made up already).
I need some way of securing the mesh (see above photos) as the tube doesn't quite hold it in well enough.
I'm going to cut some more plastic to put in the sides, which ought to stop any water coming out should it happen again.
I think I'll chop off the bottom 2" that go into the water anyhow as they'll be next to useless and just add to the weight.
Any ideas?
Thanks,
Tom

[SantaMonica]

Use Tie-wraps. Cut them off to clean, and put new ones on. Bummer about the splashing.

[worley]

That's what I did with the version 1, but I found it tended to splash around the cable tie. It could just be that the first cut I did was crap :lol: hopefully it won't interfere with the flow. I'll try it again on the new pipe and let you know.

[worley]

It worked fine this time, even with the cable ties in the same place it's working perfectly, no splashes and it's perfectly secure.
And, *drumroll*... first algae growing! :lol:
Here's the first 3 days of growth (after rubbing some algae from the tank into it to get it started)[attachment=0:bhp1fluh]TOM_3673.jpg[/attachment:bhp1fluh]
If you scroll down you can see where it has really started to build up is actually the very darkest part of the whole mesh, where the lights are it has hardly grown. Is there such a thing as too much light, or are the 6500k bulbs producing a lot of UV at only 2" away?

[SantaMonica]

I've only seen one other case of where the growth was less near the bulb. You could experiment with the distance. But I think when the growth continues, it will fill all the way across.

[worley]

It does now appear to be nearly fully covering the whole mesh, above the waterline :D
Really looking forward to seeing the first hair algae, I feel like pulling a bit off the tank and pushing it through the holes in the mesh :lol:

[worley]

Day 4 coverage, it's now nearly fully covered the patches that weren't covered before, and started to darken up at the bottom (again where there is least light)
[attachment=0:170qvdr5]day4.jpg[/attachment:170qvdr5]

[SantaMonica]

Is it lit both sides?

Any way you can add more lights?

[worley]

Yes, it's lit both sides, there's 4 x 18W 6500k PLL bulbs, two either side.
However, the most growth so far appears to be on the bottom, above the water line and below the main structure of the scrubber where the light is the least. The only thing I can think of is that these "cool daylight" 6500k bulbs are producing detrimental amounts of UV at short range. At about 4"+ from any bulb it seems to grow faster.
I don't know if this will continue when hair algae grows, we'll see.
Also, there seems to be very little change over the last day. Now I only have two medium sized black percula clowns in the tank at the moment, so there's not a massive amount of food, maybe I'll start over-feeding, or at least feeding more regularly :D

[SantaMonica]

I think it's because the flow speeds up as it gets lower on the screen. Can you increas flow?

[jski711]

lighting lighting lighting! IMO lighting has a lot to do with this method of scrubbers. i recently switched from a 65w cfl to a power compact fixture putting out 130w using 10k bulbs and the increase in algae growth has gotten much better. I also seem to be growing more "real" turf algae. i hope this helps.

Jake

[worley]

Well oddly enough, the highest growth is in the lowest light area, but I think santamonica may be right here, it is likely to be the highest flow nearer the bottom.
I have a spare pump that used to feed a skimmer that I could use, I could put on to the other side of the pipe so there are two separate feeds into the pipe that feeds the mesh.

[worley]

I've notice something else too, I believe I've actually had some brown algae die-off, rather than further growth in the last 24-36 hours.
I believe I've run out of food for the algae. Bear in mind that the tank has only been running for around 6-7 weeks now, and I only have 2 small-medium black perc clowns in the tank plus a few inverts.
I've been feeding the clowns nearly twice the amount I normally do today, and will carry on doing so, and will likely add another fish or two at the weekend.
I'm going to do a few tests quickly to verify this is the reason. I don't happen to have a phosphate test kit at the moment, so will do nitrates for the moment.

[jski711]

flow is very important yes, but believe me when i say switching my lights out has helped a ton!!!

Jake

[worley]

I've gone from 4x 15w spiral compact fluorescent @ 3000k (don't even bother, they produce so little light!) to 4 x 18w PLL fluorescent @ 6500k with mirrors either side and the bulbs at around 2" from the mesh.
So there is a huge amount of light on the mesh itself.
I checked last night, and the nitrates are at 8ppm, so it's not run out of food completely, there's a bit more buildup of brown algae in some areas, especially in the higher flow areas, so I think it's likely to be the cause.

[worley]

[attachment=0:gvb8i8y9]TOM_3872.jpg[/attachment:gvb8i8y9]

Here's the latest growth as of this evening.
Again, see the massive growth difference between the bottom and the top
You can clearly see the water line about 2" from the bottom, then the fairly heavy growth above that for another 4" or so, then very little above that.
The lighter area above the dark patch is where there is by far more light than anywhere else.
I was thinking about what you said before Santamonica, the actual flow rate in litre/hour or gal/hour will not change between the top and the bottom, the water will simply flow faster, but more thinly. The volume of water per time period won't change, so I'm more convinced now that it's the light causing the lack of growth at the top. The bulbs are only about 2" away from the mesh itself, and I've used plastic rather than glass, so there could well be a fairly high UV content to the light at that range, I'm guessing that's what is most likely to be causing the lack of growth.
I'm considering getting some glass cut to replace the plastic and try and cut down the UV output to see if that makes a difference.
What do you guys think? Strange huh?
(and yes, there is a little hair algae starting to grow, and some slightly thicker more seaweed like green algae growing about 1/4 of the way down on the left, plus loads of red, brown and some green algaes growing at the bottom)

[SantaMonica]

What is the bulb type?

[worley]

4x Phillips 18W PL-L 6500k:
http://www.algaescrubber.net/forums/download/file.php?id=6
you can't see on this photo, but where the wood across the bottom is, from there down is where the major growth is.
Also, up until two days ago the lights were on 24x7 as I didn't have a spare timer (already using about 10 of them in the house for various other tanks, including 3 for the marine tank lights!).
Maybe the 8 hours off at night will make a difference?

[SantaMonica]

That might be it!... it had no rest time, and the closer to the bulb, the worse it was.

[worley]

I'm already starting to see a small improvement in the growth in that area that was more highly lit.
Well, I'm not seeing a major drop in algae growth in the display tank yet, it has only been running for 20 days now, and on a new system with only 2 perc clowns, however I'm seeing a massive improvement in water clarity.
The water is the clearest I've ever seen in any tank anywhere, I can't believe how clear it looks. It could be pure RO/DI water it looks that good, even looking through the side of the tank is just as clear. I know everyone says that, but wow, it really is amazingly clear. I'll setup my DSLR on a tripod to try and get some photos to do it justice.
I'm going to be adding some more fish this week and see how it does with the extra load, hopefully more growth on the screen :lol:

[SantaMonica]

Good to see it's clear. Not sure why, since N and P are invisible. Also there should be more pods swarming around (unless you have a mechanical filter).

Let's see how the dead spot does with off-light time.

[worley]

jski711 is right, turning the lights off has made a massive difference already, with the huge "dead spot" where the lights are. There is large amounts of growth on there already, give it another day or two and it will be as dark as the rest with full coverage. I'll take some photos shortly :)
Interestingly, it has made almost no difference to the area that had grown already, that was further away from the lights. So up to a point, if the lights aren't so bright, or far enough away, you can get away with 24x7 growth, but with larger amounts of light, you actually need to give the algae a rest before it can grow optimally.
I'm now fully expecting to see *faster* growth where the lights are, and slower growth where the lighting is lower.
Apparently 8 hours rest for growing phytoplankton is also needed, so it does appear to be a common thing with algaes.

[worley]

Santamonica:
The water clarity, I'm guessing, is due to the higher oxygen (redox) in the water, which will break down waste faster, very similar to the way that adding ozone to the skimmer often clears the water in the tank.
It really does appear that the ATS are a hugely more natural way of keeping a marine tank, and the sort of "missing-link" we've all been looking for.

[SantaMonica]

I've heard a few other reports of clearer water too. Since you understand redox better than me, maybe you could elaborate on the process that may be occuring to clear the water, and I can post it around.

[worley]

I'm not 100% sure on why it clears the water, but I know from practice, that introducing an ozonisor into an aquarium and getting the redox level about right, (yes, it can be too high), then it helps break down waste in the water faster, so I presume that it's clearer because it helps bacteria break down the waste more efficiently.
I've rebuilt the pipe today, as the previous version wasn't giving even flow over the whole mesh. I've gone for PVC-C (was told it was MUPVC, but it says PVC-C on the side) and it cuts much more easily than the previous plastic (I think it may have been ABS, however the ABS/PVC cement glue I had wouldn't glue it to itself). The cut is much neater, and I've put a 90 degree bend to connect the pipe to the pump so that the weight of the water/pipe won't cause it to kink:
[attachment=1:2t3m7cgv]TOM_3875.jpg[/attachment:2t3m7cgv]

Also, turning the lights off at night for 8 hours has made a HUGE difference:
[attachment=0:2t3m7cgv]TOM_3873.jpg[/attachment:2t3m7cgv]

You can see the growth is nearly even across the mesh now. There are a few streaks where the water flow was virtually 0 because of the pipe "pinching" in the middle, this has now been fixed and I'm expecting the whole mesh to be brown in 3-4 days. Also, there's a fair bit of hair algae growing nicely on the mesh.

Lastly, I did a quick nitrate test last night, it's currently at 6ppm and I've been overfeeding the two perc clowns for about a week and not done a single water change in over a month (or used any sort of product like seachem prime). It's clearly having a visible affect on the nitrates already, even without large growth on the mesh yet.

[SantaMonica]

Screen looks much better. What was N to start with?

[worley]

It's now completely covered with brown algae, and there is a fairly significant amount of hair algae growth.
The nitrates before were 10ppm before starting the ATS, so they've been very slowly dropping (however as I said before, I've been doubling the food over the last week or so, and no water changes)

[worley]

http://www.algaescrubber.net/img/TOM_3897.jpg
As you can see, the brown/red algae now covers all the holes in the mesh, there is a fair amount of hair algae, and quite a lot of interesting green stringy algae I can't identify.
Best news of all, I'm no longer cleaning the glass in the tank, the glass at the top that makes the brace for the tank was covered in brown and hair algae, is now virtually clean, and for a test I've not cleaned it at all and there was 1-2" long hair algae all over it.
I'm now using my metal halides, and absolutely no brown algae on the sand (with a little help from the new blue cheecked goby).
I've now added a copperbanded butterfly fish (who is being a pain to feed, as is usual with them) and the goby, I've now trippled the food again, putting about 1.5 blocks of frozen food in the tank every day. The nitrates have still not dropped, but they've stuck at around 6ppm since the algae scrubber started and have not risen despite no water changes in 2 months and about 6 times the food being added every day.
Unfortunately the water isn't quite so clear now, thanks to the goby who makes it his mission to find every grain of sand and silt on the bottom and all the liverocks and move it around lol, but saying that, it's not too bad :lol:

[worley]

Do you guys think it's time for the first harvest to stop any die-off from the algae underneath?
I think we can say that the re-circulating design definitely works, even at the slow pace of a peristaltic pump, going at 6 litres/hour (1.6 US gal/hour).
However, as the water is very slowly fed back, I won't be getting the advantage of the higher oxygen in the water, but it certainly works as a phosphate/nitrate reducer.
I'm going to keep my skimmer turned on for now, but at a low enough volume of air that it doesn't pull anything out, but is enough to effectively aerate the tank.

[worley]

Well just got my phosphate test kit and did a test...
*drumroll*.... 0ppm :o
It's the API phophate test kit, and it was the very lightest green on the salt water card (0ppm)
That's a great result, especially as I'm now feeding tonnes into the tank, 1 block of brine shrimp and 1 of mysis plus some live brine (fed with live phyto a an hour before feeding to the fish) and some pellet foods.
However, my nitrates have just started to creep up to 10ppm, but I'm not suprised as I've put a massive amount of food into the tank over the last week to get my copperband to eat (which he now is, loves frozen mysis + live brine!), which includes 3 muscles, which he completely ignored.
I still can't get over the phosphate test, and how low the nitrates are considering there's not been a water change in 2 months and so much food has gone in.
I think I'm actually going to do my first harvest/clean of the screen and see how it goes, there is now quite a lot of hair algae on one side and a fair bit of macro, spaghetti-like, algae on the other.

[kcress]

Sweet!
So you're just pumping out of the sump to the screen and back again?

I'd probably clean the screen now.


Hey what's that comment about turning the lights off makes a huge difference? What lights? What difference?

[SantaMonica]

Hey that's awesome! Yep time for a cleaning. clean just half now, the other half in a week.

[worley]

Sweet!
So you're just pumping out of the sump to the screen and back again?
It's a re-circulating filter, so I've got a sump that is in our loft/attic, with a 6lph/(1.6gal/h) peristaltic pump that sucks water up into the sump, very slowly, then a 1200lph (317gal/h) pump that pumps water from the sump over the screen and back down into the sump and around again. Then there's an overflow at the other end that overflows the 6lph down back into the tank.

Hey what's that comment about turning the lights off makes a huge difference? What lights? What difference?
I had the lights running 24x7 for the first few weeks. I was actually getting almost no growth where the lights shone the brightest on the screen, but was getting growth at the bottom of the screen where there was little light. By giving the algae a break every night by turning the lights off on a timer, the opposite happened, and now there quite a lot of growth where the lights are brightest and less down the bottom where there's less light. Running the lights 24x7 clearly isn't a good environment for algal growth.

[kcress]

Thanks worley for the info. Now I remember the "attic" aspect.

That light tidbit is very interesting!! Important.

SM are you running your lights 24?

[worley]

I think it was because my lights were so bright and only 1-2" away from the screen, but giving it a rest every day made a huge difference to the growth.
Just going to take my first "harvest" of the screen =)

[SantaMonica]

SM are you running your lights 24?

Oh no... 18 on, 6 off

[worley]

I have visual "proof" that the scrubber works!
After having a shower I looked up and noticed something odd with the two 6mm pipes that feed the ATS and the return back to the tank (yes, they go through the bathroom, along the wall, up, through the ceiling, into our loft/attic :lol: )

[attachment=0:1tlkvmv1]dirty-clean.jpg[/attachment:1tlkvmv1]

Notice the algae build up in the "dirty" water from the tank, and that the return pipe is completely clean?

I think the fact there is any in there means that the water probably isn't being pumped fast enough into the scrubber/sump (only 6l/hour at the moment).
However, it's a great way of testing how well it works, I'm going to do a nitrate test in the tank and in the sump and compare =)

I may keep the same pipe, but split it with a T piece and put two peristaltic 6l/hour pumps (also gives redundancy) and that ought to help matters.
That, or build a new scrubber that pumps water directly from the tank

[worley]

Hehe, oh well, I tried a nitrate test, and 6ppm in both the tank and the sump, so I guess it takes longer for the nitrates to be broken down.
What I have noticed though, is that the nitrates have dropped around 5ppm in the last 2 days since the first clean of the screen 5 days ago, and in the last 2 days growth has really started again on the cleaned side. The other side that still hasn't been cleaned is really getting pretty full, so I'm going to clean it at the end of the week. As the growth slows when it needs to be cleaned the nitrate uptake appears to slow down too, which would make sense as it's not growing! So cleaning the screen at the right point appears to be fairly important.
As the growth started up again in the last 2 days the water is crystal clear again.

[SantaMonica]

If you can measure any N at all, you have plenty for growth. That means your limiting factor is strong light. With enough light, you should measure zero N and P within a few weeks or even days.

[worley]

I think possibly the limiting factor is that I've only cleaned one side so far, and only once, so I'm cleaning the other side right now, I had notice fairly substantial water quality gains a few (3-4) days after the first cleaning. While you still get water oxygenation when there's a lot of algae on the screen, you probably get slower growth, and therefore slower nitrate uptake. I'm going to make a point of cleaning it more often now. The recently cleaned side has already got good growth on it, so will do that in the middle of next week.

[worley]

Annoyingly I seem to be getting lower growth rates recently, however, it makes sense as I'm feeding half the amount due to the lack of the copperbanded butterflyfish who decided not to eat :(
However, I'm getting a large amount of red slime cyanobacteria. It's growing again in the tank, not too badly, and only on the sand, but it's annoying as the tank was virtually algae free. I've been feeding a lot of the preserved copepods to my fish and I suspect that's the source of the problem, probably containing silicates.
Of course, there is significantly more growth of cyanobacteria on the algae scrubber screen than in the tank. If the amount that is on the screen had been in the tank it would be pretty bad. I've notice it covers all other algae on the screen within 2 days of being cleaned off, so I may decide to very lightly rinse the scrubber every 2 days on both sides as well as the weekly clean until it's gone, as I've found a light rinse from a shower is enough for it to slide off.

Apart from that ...
It's been around 15 weeks since I started the scrubber in it's original design. I only clean the glass once a week, and it barely needs it. All the fish, shrimp, muscles and corals are really flourishing, growing well, showing no signs of stress of any sort, phosphates are undetectable, and I've easily saved the cost of the parts including the pump and bulbs/ballast from not having done a water change in 15 weeks, that's saved me 15 X 30L water changes (450L of water, the majority of a bucket of salt)

[SantaMonica]

Whenever cyano grows on a screen, it means there is not enough light. Your bulbs need replacing.

[worley]

Really? The bulbs are only 2.5 months old, they are 6500K though, I may replace them with lower colour temp.
Also, I'm going to replace the plastic cover over the lights with thin glass instead, should make it easier to keep clean too.
Lastly, I'm going to make it about 1" thinner and lift the feed pipe holding the screen up, above the wooden structure so the lights can be that much closer

[worley]

Well I've gone and bought 4x 18W PLL 4 pin 3500K bulbs so I'll see if it makes a difference.
I've also just got two panels of glass cut to replace the plastic I had between the lights and the screen, so it should be easier to clean.

[Patrick Pending]

You could try replacing one side with your new lights and see which works best. It could be that a mix of both produces the best growth.

Cheers,

Pat. Pending

[kcress]

That's 2 years of rated bulb life. Especially the typical crappy bulbs you normally find.

[worley]

Yes, I guess they're on much more than they're designed to be.
These are good quality Phillips bulbs, I've replaced one side with the 3500K bulbs, the new ones are General Electric bulbs.
They actually look "peach" coloured compared to the 6500K bulbs heh

[worley]

A few things...
Firstly, no noticeable difference with the 3500k bulbs after a few days.
Secondly, I think I know why my scrubber hasn't yet got my nitrates to 0, they've been fairly constant at 5-8ppm with no water changes for 3 months. I think it's lack of water flow, the rated output of the pump is 1200L/h (317 US G/h) see:
http://www.aqua-medic.de/seawater/en/14/OR%20line/ (it's the OR1200).
The screen is cut at 8" wide, which should give slightly more than 35G/h per inch
There's about 1m head to lift the water from the pump to the top of the scrubber, which puts the output at about 700L/h (185 US G/h), however, I got a bucket, and held the pipe with screen in at the same height and measured the time it took to fill 10L (1min 40 sec = 100sec = 0.1L/sec = 360L/h = 95 US Gal/h)
less than 1/3 of the rated flow. This is likely to do with the 1m head, the fact the pump is 3 years old and that there's pressure on the pump from the feed pipe that holds the screen. I may try and enlarge the slot slightly to lower the pressure (there's more flow at the far end of the pipe on the opposite side from the feed).
I may also add another pump and try and hook it up as well =)
I think that accounts for the slightly poor (it's still amazing that I've not had to do a single water change in 3 months) results.

SantaMonica: Is your 35G/h per inch rule based on actual water pumped, or rated values?

[SantaMonica]

It's actual water going through the slot.

[worley]

Thought as much, going to try and increase it, I'm fairly sure that's the reason it's not 0ppm nitrate yet.

[worley]

Well, I've managed to increase the flow by a reasonable amount, I have yet to measure it though.

A few things I've done to help:
Increased the size of the slot that holds the screen in the pipe by another 1mm or so (for a second time)[/*:m:1qdeia3h]
Cut 5x 1" cuts going 90 degrees to the slot, spaced evenly 1" away from each other in the middle of the slot (1 in the middle, 2 either side)[/*:m:1qdeia3h]
Cut the flexible pipe feeding the scrubber from the pump in half so there's nearly no slack[/*:m:1qdeia3h]
Moved the pump closer to the top of the water to decrease the head height needed to pump the water, therefore increasing pressure and flow (the water line can't drop in this case as the "sump" sucks water from the tank and overflows back in).[/*:m:1qdeia3h]

Due to the slots in the middle, I'm now noticing that the increased flow at the far end of the screen (the other end from where the water is fed in) is no longer more than the rest of the screen, it's pretty even all the way along, and also the water flow on each side is more even. For some reason, probably due to the angle that that slot was cut, there was higher flow on one side of the screen than another, this now seems pretty even.
Lastly, algae growing at the top of the screen shouldn't affect the flow so much, and shouldn't block it as easily, again, due to the slots. Time will tell, but so far, I'm not getting any splashing from these perpendicularly cut slots.

As for lights, I have seen an improvement in the type of algae growing and in the overall amount of growth since changing bulbs to the lower 3500K colour temp. I've been getting more hair, macro algaes, some interesting dark green very very long hair-like algae (6"+ long). The cyanobacteria is nearly completely gone along with less brown slime algae, both in the tank and on the screen.
And best of all, still no water changes, nearly 5 months on, with good calcium, dKH and PH. I've easily saved the price of the equipment used to make the scrubber from not having used an entire bucket of salt, and everything in the tank looks more healthy than I've ever seen in a marine tank I've kept before, I'm loving it, and so is my girlfriend!
I'm still making some incremental changes to my design, I'm in the process of replacing the clear plastic sheets protecting the lights with thin glass, easier to keep clean, cheaper, scratches less (but damn, I've got a lot of cuts on my fingers, as I forgot to get the edges smoothed, so will have to do it myself).