There is a lot of confusing data out there on algae turf scrubbers. Some wrong, some right, and a lot I am not sure about. I have been running a turf scrubber for a couple of years, in a system that is mostly fish and a few softies. Not SPS!! I have also read up and studied them quite a bit. So I am knowledgeable, but hardly some super-expert. Although I am not sure one exists. I take that back. I am sure one does not exist. Thus, everything I say below is completely true unarguable fact - NOT. H) On a personal note, I was not originally planning on having many SPS corals in my new tank, but since joining the club, I am rethinking that, and thus also rethinking my ATS strategy. So this thread is as much for me as anyone else. ------ THE BASICS ------- What is an Algae Turf Scrubber? (ATS) First off, it is named wrong. Nobody grows turf algae anymore. Basically, you have a box with a roughed up plastic screen that you pass water across, and you have bright lights shinning on that, where you deliberately grow hair algae, and scrape it off weekly. The hair algae absorbs the nitrates/ammonia/etc, and you export it by manual removal. It is REALLY good at removing nitrates. That is not hype or fantasy, it is true. A good ATS can take a 100ppm nitrate tank to 0 in less than 5 weeks. It also wipes out phosphates, some bad metals, and amusingly, can even keep a new tank from ever cycling. That part is great, but there are downsides discussed later. How do skimmers/ATS differ? An ATS works by the algae absorbing the ammonia/nitrates directly, and manual removal. An ATS does not remove dissolved organics or detritus. A skimmer works by removing dissolved organics, BEFORE they turn into ammonia, and manually removing them. A skimmer does not remove ammonia or nitrates. A huge difference. So who should consider a scrubber? The main issue boils down to how ammonia is created. A) In a fish-dominated tank, a lot of ammonia is created DIRECTLY by the fish. (pee-sortof) You end up with a lot of ammonia that a skimmer can do absolutely nothing about. Now anaerobic bacteria can of course convert a fair amount of nitrate to nitrogen. But as you near max bioload, you easily overpower the bacteria. So you end up with endless water changes, and chemical filtering. ** So, if you have a lot of fish, and just a few softies, an ATS is a fantastic solution B) In a coral-dominated tank, most of the ammonia is created by rotting detritus from food/etc. Whatever the coral does not eat eventually decomposes to ammonia. There is not a lot of bio activity directly creating ammonia. So what is the best fix - to remove those organics in the first place of course, with a skimmer. You remove the crud before it becomes ammonia, which means you never really have a big nitrate issue. ** So, if you have a low nutrient SPS dominated reef, with few fish, an ATS is pointless at best, and a coral killer at worst. C) In between - it is a tricky call. You have a mixture of fish/coral, and are sick of the nitrate problems requiring all those water changes. Do you take on the risk/setup hassle, or not? And remember, it is not an either/or decision. You can (and should) have a skimmer and do water changes, even with an ATS. --------------- MYTHS AND REALITIES ------ They turn my water yellow and spread algae to my main tank. False. Well, they do if you have a poor design, or do not clean enough and properly. If set up well, they actually REDUCE the algae in the main tank, thus making your water clearer. Done right, they can even out-compete the other algae totally. They are a huge amount of maintenance. False. No offense, but this is really a statement on your design skills in building an ATS. The concept is simple - remove a screen, scrape it, put it back, once a week. Build it right - easy. If you have to dismantle everything to clean - hard. On mine, it takes maybe twice as long as cleaning the skimmer cup. (Yes, I plan to post a video for those skeptics) Now if you factor in the water change reductions, there is overall LESS maintenance. I have never seen an ATS on a successful SPS dominated reef tank. Generally true, but it does not really prove anything. There are some experimental ATS+SPS tanks out there, but that does not prove anything either. But if you think about it, IT MAKES SENSE, since ATS systems are not really best for SPS dominated tanks. There are better methods. People experiment, then realize that. They eliminate the need for water changes. Dream on. But they do reduce it in many cases. They eliminate the need for water changes specifically for nitrate reduction. And with nitrate problems, that could be a lot of water changes eliminated. But there are a lot of other benefits to water changes. Seems like 5% / month are common, but no real data. They eliminate the need for a skimmer. Well, kinda, but a bad idea. They do nothing to reduce detritus, and even create a bit of their own. So you end up with a bunch of crud. Which yes, does eventually turn to ammonia and off to ATS. Seems like that crud is a bad idea though, and likely chokes coral. Various chemicals produce by algae, such as phenols, skatoles and creosols, cause problems in corals. It is clear that algae do produce that, and it can somehow hurt SPS corals. It is clear that improperly running turf scrubbers can destroy reef tanks, with SPS going first. It is far less clear that a "PROPERLY WORKING" ATS produces these in quantities remotely enough to be a problem. And some guess that it may even reduce them. ** This is a key and pretty big discussion. I think I will defer it a few more days until I do more research. ** So not sure if this is myth or reality. ------- THE KEY NON-CONTROVERSIAL DOWNSIDES ------- They can use a lot of power! You need upwards of 1 watt per gallon of lighting on the screen, for a whopping 18 hours / day. You need roughly 10 GPH of flow on the screen per tank gallon. That consumes a lot of electricity. Reduced by sharing return pump, and LED lighting. But a big concern, especially if designed wrong! They are a big pain to get right! Since they are rare, there are few off-the-shelf solutions. And even if there were, they need to be sized right for a given tank. Getting the screen the right size, the flow high enough, the lighting timing right, all ends up being a royal PITA! From my posts you can probably tell I like tinkering. And even I was frustrated. If done wrong, poorly maintained, or even removed too quickly, they can destroy your tank. There are two major failure methods: 1) Pollution. You don't clean enough, or screen is too smooth, and you end up with loose/dying algae throughout the tank. This suffocates and kills things. (** This is what may be prompting a lot of the phenol/chemical concerns) 2) It stops working and your tank suddenly cycles If it fails, or you forget to clean, or whatever, you need to remember that your tank is now reliant on it. Just like if you killed the beneficial bacteria, all of a sudden you lose filtration, and ammonia/nitrite will spike. They are DANGEROUS if done wrong. I got into it with the leader of algaescrubbers.net a bit on this. A simple setup goes like this. You take a bucket, pump, some pipe, drill some holes, create a little screen-waterfall. Then you get some old light sockets, and a few CFL bulbs from home depot, and put those in the bucket. Oh, and then you put your hand in there every week to clean it. HELLO!! Salt-water, falling unprotected, next to high voltage, and you put your hand in. Maybe you are nervous, and you post saying "Is this ok?" You get response like : Light is too far away. Add aluminum foil reflector. Not : That salt water will get in the socket, and could kill you. ** Notice a theme here : IF DONE WRONG ** My strong opinion is that the complexities of setup have resulted in a ton of failures, causing most of the anti-ATS bias. ------- MY PERSONAL EXPERIENCE ------ This of course proves nothing, but hey, I wrote this, so I get to tell my story. As mentioned, I have a tank with quite a few fish, and a few softies. And .... wait for it .... I had a nitrate problem. I tried a remote deep sand bad. - It helped a bit for a while, then not. I tried an expensive denitrator coil - useless. I tried chemical. - Worked, kindof. And expensive, and hard to tell when to replace. So I tried a turf scrubber. First few designs failed. But I did get it working, and for 2 years now, Zero nitrates, Zero phosphates. I got sick of the power usage, and switched to LEDs. That was a pain also, because it turns out that algae is a bit finicky when it comes to spectrum. But the right mixture of warm-white and deep-red, with a bit of blue, works great. I even did a fun experiment recently: I turned off my skimmer, and stopped doing all water changes. That lasted a long time with apparently little problem. No measurable water chemistry issues. Nothing died. But detritus was getting thicker.... At about the 5 month mark, things started going bad fast. My zoas started closing up, I lost some snails, and I started getting Cyano. (Odd combo) So big water changes, skimmer back on, and things are mostly back to normal. Still not perfect though. My theory is that the sand bed and rock were buffering things for a while, plus the detritus simply piled up way too much.