Mega Powerful Nitrate and Phosphate Remover - DIY!

[Eniram]

Yes kudos to SM for this simple yet simple algae control.

Yes sand bed is clean and algae on glass not spreading as fast as before. Will now wait for the drop in NO3 and PO4.

Steven post your algae growth on your screen, interested to see the different effects.

[stevenkoh08]

will try to post on wkends as i only got home once a wk and now busy with coming part time study

[SantaMonica]

Eniram your T5 is too far away, that's why the other side is growing more. You would be better off with a CFL. T5's need to be 2" away from the screen. Good to see the bad algae going away.

Steven it is good that your tank is clean now!

[stevenkoh08]

ha ha now my pods going crazy

too much to control time to get a pods feeding pipe fish and red mandarin

[Eniram]

Eniram your T5 is too far away, that's why the other side is growing more. You would be better off with a CFL. T5's need to be 2" away from the screen. Good to see the bad algae going away.

Steven it is good that your tank is clean now!

A bit hard to make it within 2 inchse but will think of something.

[SantaMonica]

change to cfl

[Eniram]

Problem solved i just moved the acrylic box flush with the T5 fixtures so now its like 1.5inch away. The only draw back is that only the top half where it shines on has algae growth non the less the other side is doing superbly. Day 3 and algae growth are unbelievably fast.

[Eniram]

Problem solved i just moved the acrylic box flush with the T5 fixtures so now its like 1.5inch away. The only draw back is that only the top half where it shines on has algae growth non the less the other side is doing superbly. Day 3 and algae growth are unbelievably fast.

[SantaMonica]

Video of 7 days of growth on double-layer screen:

Video of cleaning of same:

[SantaMonica]

Success updates...

Ddinox44 on the RS site: "I hated the constant drone of my skimmer which aided in the push [to get a scrubber]. I really do see an improvement and I believe my tank is healthier for it. Cleaned my screen today, tons of pods on it. Hurts to wash those critters down the drain after thinking of the money spent trying to stock them."

Docjames on the RS site: "No one in [Taiwan] has ever heard of such a thing, but my mind was determined to either be a success or a failure. At that time, the NO2 and No3 were all off the chart, unmeasureably high. That was 1 week ago. Then this morning, when I did the water check, NO2 was undetectable, NO3 was less than 12.5, PO4 was less than 0.5, Kh was 11 dkh (Sera testing kit), and Ca was 440. So I called up the lfs guy that I planned and purchased everything from, and he told me never in his business (he's had this store for decades) has he ever heard of anything like that. He had insisted that I purchased a good Protein skimmer prior to the start of the aquarium, of which I strongly refused and insisted that I'm going to be a pure ATS only filtration person. Tonight, he brought some fishes, shrimps and invert and they became the first inhabitants of my new aquarium."

Cheely13 on the RS site: "I have been using a alge scrubber for about 6 months now with no skimmer, the only thing i do is use a sock with carbon in it for my corals that i place in new every month i harvest one side every 7 days then the next week do the other side. My tank is very clear and seems to be doing very well. all tests are good. I do a 15 to 20 percent water change every week you know theres nothing like a good old water change."

Schwa on the RS site: "These things work great. I had some brown slimy algae in my display that was not going away no matter what I did so I decided to give a scrubber a shot and within 2 weeks of it running the slimy algae is gone out of my display. I am still running my skimmer and run GFO and carbon in the canister filter that powers my scrubber. My favorite, a tyree flower petal Montipora, has polyp extension that is starting to look like an acro millepora without the white sweeper in the middle. MY stuff is very happy right now the best I have seen in 3 years of reefkeeping. I am a firm believer in the algae scrubber and I think they are soon going to be here to stay for a while."

Amphiprion on the AC site: "Well, an update again. The scrubber is still progressing well. I'm starting to get a predominance of brown turf now, as opposed to the usual green. This stuff is a lot tougher, too. I'm now using a razor blade to scrape the screen, along with a toothbrush to try to get at least some of it off. At the same time, the tank is going through some algal succession as well. The bubble algae has stopped growing, and is now dying, as is much of the tough filamentous algae I had. I am getting a few patches of hair algae, however, I found that they all had one thing in common--they are areas that had deep holes with sand and detritus tended to collect. Extra particles would also settle in the algae itself, further feeding it. So, I scrubbed off the algae and removed it's food source and it has halted growth. The stuff is grasping at whatever it can to keep growing--but not while I'm around. There is a definite noticeable difference from when I started this scrubber. Feeding is at an all time high, while levels of N and P remain minimal to undetectable--PO4 about .01 ppm and NO3 undetectable. I'm feeding about 2 cubes of frozen food daily, plus pellets and coral food mix, which consists of rotifers, cyclops, and phytoplankton. I only have 2 clownfish now and a small handful of corals. I'm basically trying to test the limits of this scrubber and I've yet to stretch it even close to 100 percent."

Jstdv8 on the AC site: "So I tested my water today for nitrates and phosphates and both came back at 0. My phosphates have never been below .5 before. The screen is just starting to grow in and is no where near established like most pics I see of them, yet it seems to be working." Later: "Well, about 5 days ago I cleaned my screen and I added another light to the backside. One of my old 23 watt fully enclosed lights with the reflectors built in.

I also doubled my feeding now that I have a clown in there to help eat some of the stuff I'm dumping in there. The screen is really starting to grow some thick bubbly looking green algae on the side of the screen witht he two lights. The bubbly stuff is growing thickest on the 1" side nearest the 2nd light where there is little flow on the screen because of the tabs where it enters the pipe above (1" tabs on the left and right) both sides of the screen overall are seeing much better growth. Still a little weak, but certainly 10 times better than anything I've been seeing up until now. I'm going to play around with it and see if I can still get the same growth without the second light and continue the heavy feeding (also adding a much larger CUC) or if the second light is the hot ticket. I'm hoping to not have to use the second light as it's just more power consumption, but I'll see how it goes. If it truely needs more light I might build up something like SM's T-5 setup instead. I'm getting the zillions of miniture pods all over my front glass in my DT now. I have a mandarin and a sixline and will not hesitate to add more pod eating creatures in the future as there is way more than enough for everyone. phosphate and nitrate are still showing zero. Still have two large patches of GHA in the DT, but now that the screen is starting to grow faster I think I'll remove as much as I can during the next water change and hopefully get the screen to finally outcompete for the nutrients."

Kdc on the MD site: "built a scrubber for myself some time back. All i have to say is awesome! I have yet to see something that compares to it. it has literally taken all the work out of keeping marine fish. My nitrate level is zero, i have never seen that before, even using phosphate absorbers and skimmers. which are very expensive, and always missing with them. if anybody is skeptical dont be, this thing works and works very well."

Borge on the MD site: "don't remember how long ago I started my ATS, I've had some bad *** yellow algae (not diatoms or some easy to get a hand on algae) that grew on anything, and a heavy duty deltec 902 and ozone figthing a constant battle on those food particles, and loosing bigtime to this algae. of course its still there, but shrinking. BIGTIME. don't know any po4 numbers (seriously I hate testing for anything other than whats available at the LFS). What I do know is zero on the no3 (witch is ok considering all the algae) but no silicates and I didn't supply my tank with some new sand full of silicates! anyway today I found blank spots on my ats 6 or 7 days since last cleaning and pods ate greedy on my rug screen. now, base color on this thing is yellow for the algae, but don't you know it, it's turning green, as in long green hair, and coralline is showing up everywhere in the sump, together with a larger amount of baby snails and macros is growing... BIGTIME. Now I feel like I'm fighting a winning battle. oh... btw... my skimmer has been off for as long as the ats has been on... nothing is dying, everything looks more healthy than it's been for a 5 months. I feed just as much if not more, the fish hunts more and my banded goby is always out of his hole picking at things in the water column."

Allnatural on the MD site: "well my tank has been up for 6 weeks now. i used my ats from the very beginning. i had a very short cycle and only a small diatom bloom in my dt. it took a while for my screen to start but now it is turning green and i clean it weekly. i have yet to add any fish or corals but i did add a small cuc consisting of 3 turbo snails, 3 astrea snails and 4 nassarius snails. after the 3rd week my water parameters have been and consistantly remain perfect. nh3=0 no2=0 no3=0 po4=0 ph=8.4 cal=420 alk=13.4. i am adding my first corals this weekend. i thought i wouold see the usual algea bloom that most tanks get after the first month of operation but have yet to see any other then the initial diatoms. my copepod population is extreme and coraline is now covering my aragrocrete rocks i made. my live rock is still as healthy as the day i bought it. im so excited this tank is going to be sweet!!!!!"

Scottt on the MOFIB site: "I run [a scrubber] on my 300gal combined broodstock and grow out. I siphon the tank bottoms weekly. Water changes are done with the siphoning, about 5% of total water volume weekly. Siphoning and algal scrubbing are my only nutrient export methods. Nitrates stay around 10ppm. I add buffer to keep the pH proper. My scrubber is a 2'x2' piece of acrylic at a slight angle (almost horizontal). 150w HPS about 10" above it. I'm planning on adding a skimmer one day. The more filtration the better. But, the scrubber does keep the nitrates really low. It's a 14pair system with about 500 juveniles currently. It seems like the more food I add, the faster the algae grows. I've had no problem with algal scrubbers, only success."

Geminianspark on the MOFIB site: "I currently have two tanks running with scrubbers. My 20g biocube is a mixed reef. The ONLY filtration on that tank is a 3.5" x 9" piece of acrylic with a piece of canvas glued on top that slants across the middle chamber with a fluroscent cabinet light over it. Granted, the size is smaller than SantaMonica's recommendations and i'm not technical so i have no clue how many gph run over it but that tank has been operational with ONLY the scrubber on it since october of '09. I have macro algaes popping up ... some red grac, and some grape calepura and a couple other things i've never seen before (I'm assuming due to the regular addition of calcium, mag and alk that i dose) but VERY Very small amounts of hair algae... less than a quarter inch spots in about three places that my snails keep mowed down for me. But again, mine is undersized for the size tank it's on so that, on top of the fact that i feed pretty heavily because of my sun coral has me hooked on these as filters. I only do water changes on this tank once a month or so and i only have to clean my glass about once every two weeks. Since putting that filter on the cube, it's been the best i've ever had my cube looking.. it's stocked full. I haven't had much fun building them as i'm not very handy with things but the difference in the way my corals looked with a skimmer and how they look with the scrubber is like someone added a super vitamin to the tank. From color to polyp extension to growth... i've seen improvements in all of them with no other changes in routine other than going an extra week without doing a water change. They have my vote."

Gigaah on the LR and MOFIB sites: "I personally vouch for the scrubber cycling. It dramaticly reduces the time from when you add water and rock to when you add fish. Generally a tank needs to have the beneficial bacteria multiply to the point where it can absorb the die off from the rocks and sustain livestock. The scrubber develops faster and starts removing the ammonia/nitrite/nitrate in a capacity to support livestock faster than having to just wait for the bacteria to grow to that point. After the bacteria of course does grow to do this the scrubber keeps doing what it does and creates what I've been calling "bullet proof chemistry" in your tank. Obviously as with any system the scrubber does have to be built properly in order to fill this role but that is a pretty beaten path by now and pretty specific instructions can be found as well. If it wasn't for the wealth of information I'd probably be doing things..what I'll from now on refer to as "The old way". I hope eventually to see massive fuges (not all fuges..just massive ones) and skimmers in a junk pile along with under-gravel filters and T12 lights. I will personally certify that an algaescrubber, if built properly, will withstand the most intense bioload and feeding! These devices are just unbelievably fantastic, its almost surreal. Highly oxygenated water, eats ammonia, nitrate, nitrite like crazy. Case and point, I stirred up some crap in my tank on two occasions. My ammonia spiked to 1.5 and 10 hrs later it was .25, 12hrs later it was zero. The scrubber on my main tank is about twice the reccomended size. A scrubber 3x the size would bear a heavy heavy bioload without skipping a beat, as long as its built properly (my biggest issue at first was making sure algae cannot grow into the water supply slit and choke the flow). I can feed my 55g 6+ cubes of food in a day and it won't even flinch. They eat phosphate and control algae with ease. To be honest, with all the bennefits from this more natural method of filtering its is obvious to me this is the best filtration system.. and especially for breeding as it adds great deal of oxygen to the water and keeps the parameters stable on a high bioload. If you have any questions at all about the system please ask. I can easily spew out build parameters as I've built two for myself and a two for friends. They are extreamly cheap too. I use no other method of filtering my tanks, mechanical, chemical, biological or otherwise on any of my tanks. I refuse to in fact."

Mrbncal on the scrubber site: "Well the horizontal version was a success, it grew algae, it lowered the "Big Three" numbers like it was supposed to... but... Theres always a but, it created a lot of salt creep and spray. In short, it was a maintenance headache. I was spending more time cleaning the inside of the stand and outside the sump walls than anything else. So I have switched to an in-sump vertical model. It does everything the other one did and is quieter and there is virtually no splash. Bulbs have been clean for three weeks now. Water is supplied with an independent powerhead to an old ehiem spraybar with 1/8" slot and 3/16" holes drilled every inch (am going to increase this to every half inch) and one plastic screen. Thats it. Works great, coral and fish are healthy like never before and I am even growing some gorgonians and doing great with dendros. Still dealing with the dreaded bubble algae and I get a "five o'clock shadow" of green algae on the display glass after a week or so but that is down from "heavy growth" every couple days, a year ago. After fourteen years in this hobby, its too simple to believe it works, but but it does and I am a believer."

Vanpytt on the scrubber site: "I've read all the Norwegian and Swedish forums about this [scrubber] subject, and none have posted results and pictures before me. I can conclude that this was a great success. My water values are perfect, more or less, im not running skimmer, don't change water, and feed alot. I'm going to be upgrading my current 130l into a 1k liter system (300l of wich is a sump) with 6*39w t5ho and acrylic diy box and fixtures. I'm not going to run anything except getting an UV filter for killing paracites and the well sized scrubber as standalone filtration in the sump. Will be posting pictures once the building starts."

Wak on the scrubber site: "Well i have a ten gallon nano reef. The nitrates in this tank were always around 20ppm, the filtering was a skimmer + small cannister filter and 10 pounds of live rock in the tank. Four weeks ago i found this info and decided to build a scrubber, I went for a one sided 30 degree sloping design the screen is 10 inch long by 2 inches wide and lit by 2 8watt linear t5 3500k tubes, flow about 200 litres per hour. Two weeks ago i took out the skimmer, Today my nitrates in the tank hit 0 for the first time ever thanks to this info"

Fholguera on the scrubber site: "I'm very happy with the results, my corals look very happy and the algea in my rocks is disappearing, the glass last longer without cleaning and the sand looks whitier. The kind of algea that grows in my scrubber it's starting to change, first it was a lot of filamentus and brown algea and now it's almost all filamentus and a little bit of ciano I think."

Bridgeport on the scrubber site: "Since I started this 55gal. close to two years ago, I had nothing but trouble from the start. Most of it was due to my lack of experience. The last time I had saltwater tanks was back in the 70's and as you know a lot has changed since then. Was plagued with green hair algae. After that cleared, then the red hair algae started, and lots of it. I started a scrubber about a year ago but didn't have it really going properly until about 5 months ago. Since then i am getting lots of growth. Most of the red hair algae [in the dispay] has disappeared. Just disconnected my hang on refugium about 2 weeks ago. The Cheato was dead and fouling the water. I did take the rocks out several months ago and cleaned them. Its a lot of work but it really helped to clean up the tank. My Algae Scrubber has gotten the Nitrates to 0 and the Phosphates to 0 and has disintegrated most of the red hair algae [in the display]."

Ihfarmboy75 on the scrubber site: "Ok, I'm sold. I have this scrubber on my 125 gallon African Cichlid tank and when I set it up on march 12th, my nitrate levels were 120 ppm. I was doing weekly 25-35% water changes and still couldn't get them under control. In a little over two months my nitrate levels have dropped to 5ppm and I would imagine they'll be zero in a few weeks."

[SantaMonica]

Here is the longest I've let it grow... two weeks. The screen was full and touching the acrylic walls at 7 days, so it had another 7 days to fill upwards:

[SantaMonica]

The new scrubber FAQ for 2010 is now posted:

http://www.algaescrubber.net/forums/viewtopic.php?f=9&t=68

[Eniram]

Thanks again SM for your efforts and contribution to this thread

[Goondoo]

Thanks again SM for your efforts and contribution to this thread

Finally pick my butt up to do some modification to expand the slit. How the flow is a lot more even

Can't really see from the video, but well... its about there

[SantaMonica]

Well I thought it couldn't grow any more in two weeks, but this time it reached the top of the window and was getting ready to spill out the end. My other scrubber was not very grown yet, so I did not want to clean this one today, but I thought I better before it spills. Tests today were N02=0, NO3=2, P=.015? (very faint blue). Feeding is one silverside per week to the eel, 4.8 ml/day continuous feeding of Oysterfeast for the corals (very low amount, currently), and misc nori/daphnia for the fish. Pics:

Video:

.

.

[SantaMonica]

Finally getting the 25 nano scrubber to have consistant results. Am testing one side of it here, on a FW 10 gal with some tetras, catfish, suckerfish, and a discus. 0, 0, 0, when feeding one frozen cube blood worms a day. No water changes, and top off with tap water (no chlorine remover added)...

[SantaMonica]

Great Barrier Reef Aquarium

Many people who have not built a scrubber properly (after August 1988) often say how the Great Barrier Reef aquarium was a scrubber "failure" because the corals did poorly. Apparently these people have not done much reading. In the early days of that aquarium, the scrubber was doing it's job great:

1988:

Nutrient Cycling In The Great Barrier Reef Aquarium

http://www.reefbase.org/download/download.aspx?type=10&docid=10506

"The Reef Tank represents the first application of algal scrubber technology to large volume aquarium systems. Aquaria using conventional water purification methods (e.g. bacterial filters) generally have nutrient levels in parts per million, while algal scrubbers have maintained parts per billion concentrations [much lower], despite heavy biological loading in the Reef Tank. The success of the algal scrubbers in maintaining suitable water quality for a coral reef was demonstrated in the observed spawning of scleractinian corals and many other tank inhabitants."

But did you know that they did not add calcium? That's right, in 1988 they did not know that calcium needed to be added to a reef tank. Even five years after that, the Pittsburgh Zoo was just starting to test a "mesocosm" scrubber reef tank to see if calcium levels would drop:

1993:

An Introduction to the Biogeochemical Cycling of Calcium and Substitutive Strontium in Living Coral Reef Mesocosms

http://onlinelibrary.wiley.com/doi/10.1002/zoo.1430120505/abstract

"It was hypothesized that Ca2+ and the substitutive elements Sr2+ and Mg2+ might [!] have reduced concentrations in a coral reef microcosm due to continuous reuse of the same seawater as a consequence of the recycling process inherent in the coral reef mesocosm."

"The scleractinians (Montastrea, Madracis, Porites, Diploria, and Acropora) and calcareous alga (Halimeda and others) present in the coral reef mesocosm are the most likely organisms responsible for the significant reduction in concentration of the Ca2+ and Sr2+ cations."

"Ca is not normally a biolimiting element, and strontium is never a biolimiting element; HCO3 [alk] can be. It appears that, because of a minor [!] limitation in the design parameters of the mesocosm, these elements and compounds may have become limiting factors. [...] It is surprising that the organisms could deplete the thousands of gallons of seawater (three to six thousand) of these elements even within two or more years [!!].

"The calcification processes are little understood."

So then in the late 90's, the Barrier Reef aquarium start using up it's supply of calcium, and the folks there said "the corals grew poorly". Really. No calcium, and the corals grew poorly. So they "removed the scrubbers" and "experimented with the addition of calcium" sometime after 1998. Then in 2004 it "definitely improved a lot". Really.

[SantaMonica]

Low-light Scrubbers

Here is something new, different, and untested. I have not built one yet, but it should work for either SW or FW if the size and flow are correct. It is a vertical scrubber that you hang on the wall, and it requires NO electricity. It is a "low-light" scrubber:

I got the idea when reading a study about algae growth in freshwater streams:

"Algal Response to Nutrient Enrichment In Forested Oligotrophic Streams". Journal of Phycology, June 2008. http://www3.interscience.wiley.com/journal/120083425/abstract

"Algae inhabiting forested streams have the capacity to acclimate to low light intensity. These light conditions affect their photosynthetic efficiency, but do not impair growth rates, in particular, in the case of thin diatom-dominated communities."

In other words, they don't filter as much per square inch (or per square cm) of area, but they do operate on very low light. Apparently it is mostly diatoms that grow in these low-light conditions.

The advantage of a scrubber like this should be obvious: It requires no electricity to power the screen. It still requires a pump, however, since the top of the scrubber would (probably) be high above the top of the tank. The scrubber is designed to operate on the light already available in the room, which would vary greatly depending on how strong the light bulbs are in the room, and how much sunlight comes in through the windows. The more average light the room has, the smaller the scrubber can be. The less light, the bigger it needs to be. Basically, the scrubber uses more area to make up for less light. And since the light is so low, the type of algae that is able to survive is (apparently) mostly diatoms.

Just as with regular scrubbers, the wider the unit it, the more flow is required. So in the spirit of keeping it from consuming too much electricty, a smaller pump could be used if the unit were narrow and tall. But the bottom of the unit will need to drain into either the tank or the sump, so there will be a limit to how low the bottom can be. And the limit to the top will be the ceiling. A tradeoff will need to be made, maybe so that it looks like a vertical picture on the wall. Fortunately the flow does not need to be as much as a regular scrubber, since it is one-sided only.

It will have to be experimented with to see if a clear cover is needed to stop any water dropletts from splashing out. Many people have decorative waterfalls of the same size as these, and they have no cover on them, so maybe water dropletts getting on the floor will not happen. Evaporation would be high though, and this might be reason enough to consider a clear cover.

Cleaning could (apparently) be done by having a removeable screen or porous sheet, just like a regular scrubber has. It would be big though, and would drip as you took it out. Also it probably would not fit into a sink, and so would need a bathtub or shower (or outside) for cleaning. A possible fix for this might be a very flexibe woven plastic mesh, which you could fold up like a towell and easily clean in a sink. A material like this might not lay down flat when it's in the scrubber, however.

This type of scrubber would be easiest to try for somebody with a cement floor, lots of wall space, open widows or skylights, a low sump, high ceilings, and a big sink or patio for cleaning. I have no idea of the size required for the unit.

[Creetin]

hey guys i am back to using the scrubber. my first version was choked and thus a failure.

am using zeovit now but it seems to be unable to keep with with the algae growth. so after frustrating for a few weeks, suddenly decided to do a quick scrubber... lets call it no frills scrubber, done in 3 hours with old equipment and parts. the screen seen here was actually my 1st screen, cut out to use.

this time i opted for a quick and dirty way out. just a screen attached to a PVC pipe, with hooks to hold on to cables ties (luckily i had the tank maker fasten 2 wooden strips to my internal sump compartment). the screen is basically hanging and a pico 1200 jets the stream (flow around 1200l/hr) across the screen. i must say the effect and flow is much stronger than my previous one. finally added a anti splash screen behind and on the right.

Lights should be back to the same one i previously DIYed, just a tad smaller but same philips 20w bulb.

hopefully it will clear most of my algae quick.

[Creetin]

Santa, could you refresh my memory on the usage:

1) day 0 - leave the lights on for 24 hours

2) 7 days - 14 days - check for growth, either clean at 7 days or if still clean, leave till 14 days

3) 14 days - first clean

4) after which clean weekly.

[Eniram]

Lights are to be run 16hrs ON, 8 hrs OFF. To provide maximum growth the ideal wattage of the lamp should be 36W (min)and using WARM WHITE.

Clean the screen every 3 days, the initial growth would be brown thin algae. After a few weeks you'll see some green hair algae growth within the brown algae growth. Now you clean it every 5 days, Overall, a new screen has darker growth because the nutrients in the tank are higher. After a few cleanings (i.e., a few weeks), the nutrients in the tank should be less, and thus the growth should start getting greener.

If your screen NEVER grows green even after 8 weeks, it means your scrubber is just not strong enough for your amount of feeding. You can:

o Add more lighting (more bulbs are better that one stronger bulb)

o Rough the screen up more

o Increase the flow

o Reduce the feeding

o Add another screen and bulbs (meaning, a second scrubber)

Remember though, that dark brown/black growth STILL does filtering; but it should be cleaned every 5 days instead of 7. If brown/black gives you enough results, you will have no need to worry about changing things.

[SantaMonica]

Creetin good to have you scrubbing again. See the faq for more updated info:

http://www.algaescrubber.net/forums/viewtopic.php?f=9&t=68

[Creetin]

can someone tell me why has e design of scrubber grown horizontal instead of vertical?

always tot vertical saves space, much like high rise buildings.

i noticed e design now is of an internal box system.... so keeps splash out...! cool

[Creetin]

got e lights running.

if it cant keep up then i shall diy a larger one. this one is a lil small

[SantaMonica]

Horizontal is OK if you want to experiment, but if you absolutely must have results, go vertical. The biggest operational problem with horizontal is that as algae builds up on the screen, it blocks flow to areas downstream from it. This is because the water is not flowing very fast, and it cannot "jump" up and over the new growth. So the more algae, the more blockage, and thus it is self-limiting unless you have a LOT of flow. With a vertical, however, the flow is rapid and goes right over new growth. This is the reason that a horizontal needs 4X the screen area, so it can make up for less performance.