My Basic Guide to Algae Scrubbers

Ecotech Marine


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Apr 13, 2019
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Algae scrubbers, also referred to as Algae Turf Scrubbers (ATS), seems to be an increasingly popular topic on here. So I decided that instead of saying the same things to people I could just write this guide and refer to it. Now given that I've really only ran two algae scrubbers (but at least got them both to grow), I've still learned a lot about the topic. Or at least enough to give people a basic understanding of how this works. Anything more complicated than this should really be the finer points. So keep in mind this isn't an all-inclusive guide. Just a basic guide to help people get into it who haven't done it before or who are on their first one having issues.

Also I should say that everything I've learned, I've learned in my attempt to go water-change free. That is, without having crazy amounts of nuisance algae of course! I succeeded at this in freshwater, but with that you have plants and plants help a lot! With saltwater I'm focusing on powerful scrubbing as a way to finally eliminate water changes. I say this because by the time you get a powerful enough algae scrubber to work in the first place, you might be able to say goodbye to water changes forever! In other words, perhaps the best strategy involving algae scrubbers also involves not doing water changes. Or at least understand where I'm coming from.

Part 1- The scrubber itself (Before you buy!)

Now there are a lot of different algae scrubbers that use slightly different methods to achieve the same thing. All methods involve running water (aka flow) over some kind of surface and shining light on it. Just look at Santa Monica Filtration's product line for example. I think they have just about every kind of algae scrubber you can imagine! Many of them use an air pump to make bubbles that create the water flow. Others are waterfalls that use water pumps to pump the water over a sheet, that's usually lit from both sides. Personally I have more experience with Santa Monica's upflow (as in air-pump powered) scrubbers. To my understanding, waterfall scrubbers can have more evaporation. However many nowadays have covers that probably mitigate that substantially. Suffice it to say upflow and waterfall designs can both work!

The next thing to understand, and this is absolutely critical: Your scrubber has to have very powerful lights. If your scrubber is not very strong, you just can't expect algae to give up in the display to be in your little scrubber. Yes, some scrubbers can cost a lot of money. But this is one of those things where you either "go big or go home". If you don't, you might end up with a useless scrubber (Like me, unfortunately!). Remember, you are trying to create an environment that is better for algae than your display. And depending on your display lights, that isn't always easy. The brighter the lights in your display, the brighter your scrubber is going to have to be. But this leads me to the next part.

Also in the spirit of preparation I'd like to say that problem rocks are something that fights with your scrubber directly. I haven't actually done it but in theory if you can get as much phosphate out of your rocks as possible, you could make this entire battle much easier. To my understanding this can be done with lanthanum chloride. I deeply wish I would have known about that before I got started. I would have treated my rocks with that, with great prejudice! Rocks that are rich in phosphate, plus your bright reef lights, plus your gyre/flow pumps...That is just asking for nuisance algae. So please take your rocks and their phosphate levels seriously! Algae loves phosphate, and you had better believe rocks can have it!

Part 2 - How the technique of algae scrubbing works and how to apply it

Algae scrubbers work by purposefully growing a ton of algae in the scrubber. The growth of this algae will definitely strip the water of nutrients, namely phosphate and nitrate. So it's like if you had a big trained mouse to go and eat all the crumbs in your house, who could eat faster than all the other pest mice. The pest mice would eventually start to starve. Especially if the big mouse was out all night eating everything and the little mice only had an 8 hour window to eat! That is more or less the analogy I would use to describe what you're trying to do with algae scrubbers. Also I should say that algae scrubbers don't need to be seeded with anything. Simply running your system's water over them, plus light, will grow algae on its own.

Now the second part. How do you apply that technique? Well, the first step is in part 1 of this guide. Get a scrubber with a lot of flow and a lot of light! Ok, assuming you've taken my advice, you've given yourself the most chance of success with a scrubber you could possibly have! But it still isn't everything. Sometimes getting growth started isn't easy. But here's my advice for getting it started: Cease all other means of nutrient export. Meaning no GFO, no Nopox, no water changes. (Though to be honest I don't recommend turning off your skimmer. That said it's debatable whether you even need a skimmer or not, but I'm yet to actually do that particular experiment!) This will likely cause there to be enough nutrients for algae to grow both in your scrubber, and on the rocks in your display. Depending on where you are nutrient-wise. I've always wondered if I would have gone into this with the scrubber I have now, how much easier things would have been. It could be that if the scrubber was introduced soon enough, it could just grow all the algae in your system forever! In theory I think that could happen! But you would have to have a lot of foreknowledge.

Here is one phenomenon that should definitely be mentioned: Sometimes when you actually get your scrubber going, it pulls so much phosphate out of the water that your rocks will begin leeching phosphate out into the water. This will cause nuisance algae on the rocks to actually increase! However by manually removing your nuisance algae, you're taking those nutrients out of the system forever, which of course I have to recommend doing. Especially if you are trying to get your scrubber going. Leaving the nuisance algae alone isn't good for your scrubber since the opposite of what you want may very well happen! The display could out-compete your scrubber. You have to know that the more algae growth you have, the faster that algae is going to be taking nutrients out of the water. So don't leave that display algae alone! But DO leave you scrubber algae alone! As much as possible, until you have to harvest it to make room for more. I believe algae, as well as plants, do best when they're left alone (but with nutrients, light, and flow of course). So as much as you want to check your algae growth, if you must do it, try to do it as unobtrusively as possible! Don't touch the growth or mess with it in any way. These are some tips to help your scrubber and hurt your nuisance algae at the same time! Anything that hurts one, helps the other! And vice versa. It's a zero-sum game with this algae! And be sure the winner is your scrubber! Both might win momentarily, as the phenomenon I mentioned earlier can easily happen. However I see that as the scrubber winning. Either that or your water is so nutrient dense that it can support both the scrubber and the algae in the display. But hopefully not many of us fit into that category!

Also another tip for helping your algae scrubber get started: Reduce your display photo-period down to 8 hours. And on the flip side of that, up your scrubber hours to as many as the unit can handle! I highly recommend 20 hours a day if your scrubber gets hot. If it wasn't for that, 24/7 would be the best! Algae does not need rest!

Another tip from experience: Be sure that you have as much flow through your sump as possible! I made the mistake of trying to get away with the minimum, and what happens is that your sump becomes very clean but your display will only be getting that small trickle of clean water! That's not good for algae scrubbers, either.

Part 3 - Where do scrubbers fit into your overall nutrient export plan? Also, why scrubbers?

Yes there are different philosophies regarding the place of algae scrubbers in the overall nutrient control strategy. My strategy is to have one really amped-up algae scrubber and that could very well be the end-all be-all if you do it right. To me it's the simplest, easiest, and cheapest in the long-run. I don't believe in doing anything else as a means of keeping nutrients down. GFO and so forth needs to be replaced, so does pretty much anything else. Besides that stuff is not natural. I believe nature is the best solution to a nature-based problem. Algae is great at filtering lots of harmful things! More than just your phosphate and nitrate. It also filters out heavy metals and other generally toxic things. All while consuming CO2 and outputting much needed oxygen for your fish! Which I believe increases the pH..which can keep your pH stable through the night! As far as I know, it's the perfect answer to just about everything! It's just a matter of getting the thing to work and to work consistently. So all this should probably answer the question: "If I have an algae scrubber going, can I have X nutrient export method going at the same time?" And I can't say I have a ton of experience trying to combine this method with others, aside from skimming. But I can only imagine that other export methods might stunt the growth of your scrubber. So if it's something that the scrubber would have taken care of, then why did you spend money on the scrubber? If you spend money on it you should get the most out of it that you can. So I guess first get the most out of the scrubber and if it's still too much, then perhaps try your other methods if you must!


The best way to use algae scrubbers is to fully understand them and the factors at play. If you fully understand them, you should be able to correct or avoid possible pitfalls without needing to try to ask questions about your particular situation. Hopefully I've at least done a decent enough job of laying out the basics. Remember: It's a battle! The golden rule of algae scrubbing is that the conditions in your scrubber have to be better than the conditions of your display! Algae will grow in the best place for itself. It's like if you had two houses. If one was better, you'd probably move in and mostly forget about the other one! You'd move into the house that was best for you! The same is true in this algae situation! Algae is a great thing. But it needs to do what it does in your scrubber and not on your rocks! Flow + Nutrients + Light = Algae! Rocks can give algae the phosphate advantage, but there are ways to tip the scales in your favor!

Anyways, good luck out there and I hope this guide helps!

salty joe

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Dec 14, 2015
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Medina, Oh
I use a DIY algae filter and the last time I rinsed the screen in tapwater after scraping, the algae left on the screen mostly died. Maybe it was because the water was cold, IDK but from now on I'm using a little tank water to rinse the screen.


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I use a DIY algae filter and the last time I rinsed the screen in tapwater after scraping, the algae left on the screen mostly died. Maybe it was because the water was cold, IDK but from now on I'm using a little tank water to rinse the screen.
you may have chlorine in your tap water, idk just a thought


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Denville, NJ
I use a DIY algae filter and the last time I rinsed the screen in tapwater after scraping, the algae left on the screen mostly died. Maybe it was because the water was cold, IDK but from now on I'm using a little tank water to rinse the screen.
You don’t need to rinse it with water at all, just use a credit card to scrape the thick layer of algae off. You want to keep the seeded algae in the holes of the scrubber screen so that it keeps a consistent nutrient draw. I have scrubbers on all of my tanks.

I still have a skimmer on my tanks and run chemi pure blu/carbon on two of them. Algae pulls nutrients but not toxins in the same way carbon does.

What temperature do you think it too high for your reef tank?

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