Algae Scrubber

I believe that the health of reef tanks inhabitants is most often at the top of the concern list when owning a reef tank. In maintaining a reef aquarium the hardest struggle to deal with is usually the quality of the water. If you allow your water to be untreated the corals and fish begin to suffer or die and algae begins to take over your aquarium. There are a few options to battle this. Water changes, Biopellets, GFO, and Carbon to name a few. I have used all of them and currently still do. However, I’m going to test another way of filtering water on my new propagation system which I have high hopes for–an algae scrubber.

As discussed in my other posts, many of you know that I am extremely interested in propagation of corals and anemones. One of the many struggles with a propagation system, or any saltwater system for that matter, is the control of nutrients in the water and the algae which inevitably follows. As with any animal, corals need to be fed. In a propagation system you want to see as much growth as possible and you can’t get that by relying on light alone. I know a lot of people will argue with me that this isn’t true. However, I have found that I get better results by feeding my corals. Since I do feed my corals very heavily, it gets very expensive keeping the water quality as clean as possible because numerous water changes are required on top of running so much carbon and Biopellets. I realize a lot of people say or post on the internet that “Acans, Zoas, and Anemones prefer poor quality water”. I have tested this theory out and have found it to be completely false. So far I have not found any corals which actually prefer the  water to be dirty. Based off my own experiences I believe one hundred percent that corals need to be fed no matter if they are LPS, softies, or even SPS. The downside to this, however, is that if you are constantly dumping nutrients in to your tank you are most definitely going to end up with dirty water. This will result in poor health and color of your corals along with an algae bloom which will make things even worse. To avoid this on a propagation system, you would have to spend a small fortune on water changes, bio-pellets, carbon, reactors and the pumps to run them. Heavy feeding and maintaining clean water was getting very expensive so I began my search for other options. How can you have the best of both worlds: a lot of feeding for growth but also maintaining clean water without breaking the bank? Hopefully the answer is an algae scrubber. I did a massive amount of research on Algae Scrubbers and felt that a DIY algae scrubber was something that I would like to try.

First off, what is an algae scrubber? The idea is that if you’re going to have excess nutrients in your system then you’re going to have algae no matter what. Algae is not all bad, it soaks up nitrates and phosphates in your system which in turn cleans your water. The problem is that it looks terrible, spreads everywhere and can smother and kill your corals. An algae scrubber promotes the growth of algae but in a specific section of your saltwater system. By supplying extra light, oxygen, and water flow in one area of your tank you will cause the algae to grow in your scrubber and not throughout the rest of the reef. The algae growing in the tanks will not be able to compete for nutrients with the scrubber algae since the conditions are not as optimal and will soon die off. It is the same principle as putting “Chato” in a saltwater system sump, which is very common. According to online research regular hair algae is better at nitrate and phosphate removal which is why I’m choosing an algae scrubber over a large Chato packed sump.

First step was getting the frame built. It was designed to sit above a 100 gallon Rubbermaid tub which the propagation tanks drain into. The frame will support the algae scrubber, the ozone reactor (jury is still out on if I feel like this is needed or not), and four reactors for carbon and Biopellets. The algae scrubber was built to twice the recommended size as what online research had indicated, just to be safe. The frame was made from metal and covered in high grade rust resistant enamel. I was very leery about putting metal so close to the tank. However since the frame needed to support electrical equipment, running water, and reactors I chose safety over the risk of having metal close to the tank (So far no invertebrates are showing any sign of stress so I don’t believe any metals are getting into the water). The algae scrubber area is encased behind Plexiglas so that the water does not splash or ever hit the metal or electrical equipment. The actual algae scrubber section was made out of PVC pipe with zip tied quilting mesh attached to the water outlet for the actual area where the algae will grow. Next a 3200 GPH pond pump was added to push water up to the algae scrubber and to power all the filter reactors. This was overkill on the GPH, but I wanted to be sure I had plenty so currently a lot of the water is bled off and just pushed back into the Rubbermaid tub.


Next step was hooking up the lights and the filter canisters. Two canisters  contain Biopellets and the other two run activated carbon. The lights are using a plain CLF bulb.

Water was started and success, everything looks good! [only back half of lights are hooked up so the video could show water movement]


When I first started using the scrubber I had the algae lights on for the same length of time my tank lights were on (It is suggested to run your lights for 18 hours on the algae scrubber).  This wasn’t intentional I just didn’t have an extra timer sitting around. So at the beginning the algae growth was slower than expected. I didn’t have a lot of stray nuisance algae as it was due to the fact that I did so many water changes, but any stray hair algae I had in my prop system I could see it was already dying off and melting away.

Here are some growth pictures over the course of two months.   [Note: The light was left off the bottom right on purpose to observe the algae growth]

Five days after setup.

15 days after setup


1 month after setup  — Lights changed to 18 hours a day instead of 9.


2 months after setup


After two months of running overall I am very happy with the results.  I can feed the LPS heavily several times a week and still keep SPS in the same system.  Any nuisance algae I had in the tanks has disappeared.  I still do water changes monthly but that is to put trace elements back into the system, not to keep the water clean.  As of my last water test my nitrates and phosphates were not measurable.  My ORP has raised about 75 points which is great and my PH is more stable since the scrubber lights are on for 18 hours a day.  The only drawback I have had is that about a month and a half into the experiment I had a large unexplainable phosphate spike which i believe has something to do with the algae in the tank dying so rapidly but I’m not sure.  Other than that I would say the experiment was a huge success and as long as the next few months follow this same great results all my reef tanks will have an Algae Scrubber on them from here on out.

Update 04-02-2013

I currently clean the algae screens once every 2-3 weeks. It’s a very simple process. I Pull the screens out and I actually scrape them off with the same scraper I clean the glass with.  It doesn’t get all of the Algae off but I prefer it that way so that the screens do not need to be reseeded. I believe this actually makes the Algae grow faster by not cleaning it all the way off.  I just thought i would show how much Algae the scrubber grows in a two week period.  Just think all this could be in the tank instead of being used to clean the water!









8 thoughts on “Algae Scrubber

  1. Nice build. Glad to see that you like it so much. I gotta say though, it’s huge! Any reason why you chose the size to be that large? The reason I ask is that originally it was thought that you should size according to the volume of water of the system. That was revised so that it was more based on the amount you feed per day, on average. So instead of 1 sq in of screen per gallon, it’s 12 sq in of screen per cube of food fed per day. It helps a lot because of space reduction, light reduction, easier to get a higher flow rate across a smaller screen, etc.

    So if you think that might make your scrubber easier to maintain, more cost effective, etc – consider it. But, as the old adage says, if it ain’t broke, don’t fix it!!

    Good to hear that you will be putting one on your future tanks as well. I think they are a great tool to have in the toolbox, no matter what other filtration you run. Of course, I’m biased since I build them LOL!

    1. Hi Bud,
      Thanks for the comments! Yes i agree the size of the scrubber is probably overkill since i feed probably 2 cubes a day (if that) on this system. Never testing out this formula myself and having an extra 3200 gallon pump laying around i decided going to big might cost a little bit more but to me that was better than going to small and not having a proper test or enough mesh to handle the size of tank with feedings.

    1. Hi Dave,
      Yes I have. I’m currently building a grow-out system which is basically two 220 tanks plumbed together and sharing the same sump/filters. In this system the idea is to keep the algae scrubber you see in this article but also add an upflow algae scrubber so i can have more filtering but also see which one will build up more algae.
      Thanks for the comment!

    1. It is doing well, not growing near the algea it used to which I think is a good thing. Tank parameters are all in check so it did its job when I really needed it. Thanks for asking

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