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Algae Scrubber Basics 12 of 14

Posted 02/19/2012 at 08:36 AM by Floyd R Turbo

Electrical Protection

This should really go without saying, but you should always plug your lights into Ground-Fault protected receptacles (GFCI).

Always use waterproof sockets for your CFLs and end caps for your T5HO lamps. This is a little more expensive, but is necessary to avoid corrosion and electrocution. Generally, waterproof CFL sockets do a pretty good job of sealing the base and socket from moisture, but they still should be silicone sealed for an extra layer of protection. T5HO waterproof end caps do an excellent job of sealing the end of the lamp, but the wires that feed into the bottom of the sockets are not sealed, so after all wiring is complete, you need to fill in the bottom with silicone caulk.

You can't see it, but there will be tiny amounts of salt spray that will build up where you screw a CFL bulb in, and also where you make electrical connections. When the buildup gets thick enough, it can short out and trip a breaker or GFCI receptacle, or shock you. So each time you replace a CFL screw-in lamp, re-seal it. You should be able to pour water over it without it causing a problem (but don’t try it). Use GE Silicone I Door & Window caulk, which is generally accepted as aquarium safe, especially since you don’t intend for it to be in direct contact with water anyways.

Moisture protection for LED fixtures, DIY or off-the-shelf, is the biggest issue facing the progression of LED Algae Scrubbers. At this point, it’s just a risk that you either take or try to mitigate against. So far, no build that I have seen has incorporated adequate moisture protection, aside from passive cooling and spray-coating a DIY fixture.

Screen Break-in Period

Since the time frame by which you will see certain types of growth largely depends on the bio-load, initial nutrient conditions of the system, and strength of the scrubber, not everyone will see the same growth progression. Some have taken months to get a full screen of green growth; others get great results in just a few weeks. However, every screen must go through an initial break-in period, and that is relatively independent of anything else. Usually, the first week or two of growth is almost identical for any scrubber; after that, different system will tend to diverge depending on the conditions.

When you first start up your algae scrubber, even with the screen significantly roughed up, it is still relatively slick on a microscopic level. It is plastic, after all. The reason behind roughing up the screen is to vastly increase the surface area, and to give long strands of algae something to hold on to.

As the tank water cascades over the screen, there will initially be a buildup of brown slime, similar to what you see on the insides of your tank plumbing (and like what you clean out of your pump). Over time, this growth on the screen will strongly adhere to the screen. The bond is so strong that you would have to soak the material in vinegar to completely remove the algae. This may sound familiar to anyone running pumps or powerheads (which should pretty much include everyone).

During the break-in period, this brown layer is easily rinsed away (with a sink sprayer, for instance). For the first few weeks, a very light cleaning is all that is needed – just lightly running tap water. A gentle swipe of your fingertips will take most of this layer off, but will leave enough behind that if you put a new screen next to it for comparison, you will see a slight color difference. You want to leave behind anything that doesn’t easily wash away, including whatever is growing in the holes. You definitely don’t want to scrub the screen with a brush of any kind. Any growth you get for the first few weeks should be easily removed with your fingertips (not nails). If you happen to get some long green hair algae strands, you should be able to remove those with your fingernails (gently).

Usually after the second cleaning, the screen will have developed a foundation upon which algae will be able to form a good bond. What type of algae will grow next is dependent upon factors stated in the first paragraph of this section. Regardless of the type of growth, the screen will continue to mature to the point where if and when a thick mat of algae grows, it will stay firmly attached to the screen. This is usually attained around the 4-6 week point, and can be verified when algae grows inside the ‘squares’ of the screen and does not come loose during cleaning.

My screen break-in cleaning technique progressed as follows:

Week 1: Rinse with slow running tap water

Week 2: Same, except used fingertips to rub screen

Week 3: Rinse off with running water, then rub with fingertips

Week 4: Same

Week 5: Same, had to use backs of fingernails in some places

Week 6: Algae firmly attached. Used back of fingernails across entire screen (now I use a plastic scraper)

Every scrubber will have slightly different growth progression, but the guideline above gives you an idea of what to expect. See “Algae Growth Types” for some additional information.

Cleaning the screen

Cleaning the screen should be done remote from the tank. A common complaint of the past was that an Algal Turf Scrubber turned the water yellow, but that was because algae was generally removed from the tank with the screen in place, or it wasn’t well rinsed.

If you have lots of pod-eaters in your tank, and your screen is nice and green (no slimy growth) you can consider swishing the screen in the tank every once in a while before cleaning. I did this a few times, but I really don’t anymore.



Screen cleaning should be done in room temperature tap water. The reason is that freshwater kills pods that are continually munching on the screen. There will be millions more in no time, you just don’t want them causing algae to detach between cleanings.

I use a cutting board and a plastic pot scraper similar to this one https://www.pamperedchef.com/orderin...Id=241&catId=9 to scrape the algae off the screen.

You will need to use an old toothbrush or a stiff-bristled scrub brush to remove any algae that grows on the smooth area at the top of the screen. I also use a scrub brush to remove any red turf. Red turf seems to grow well in the lower light areas. I have since trimmed these areas off the screen since I needed to make it smaller.

The slot tube also should be cleaned by scrubbing with a brush and rinsing. If you have an enclosed box device, you will likely need to clean algae out of there occasionally too. I have to do this every cleaning, it’s amazing how well algae attaches to a smooth surface.

After all the scraping and scrubbing is done, give the screen a good rinse (15-20 seconds) in fast running water.

Cleaning frequency

For the first 4-6 weeks, cleaning every 7 days is probably a good idea (see the ‘Screen Break-in Period’).

The exception is the ultra-high nutrient system that results in a black slime coating forming every 2 or 3 days. Such growth must be completely removed, as soon as possible - at the most every 3 days (see “Algae Growth Types”)

The general rule has been to clean your screen every 7 days. This is still the rule for single sided and non-vertical Algae Scrubbers.

If you run a double-lit vertical Algae Scrubber, now it is allowable to let the screen grow as long as 10, and in some cases, 14 days. Again, you need to pay attention to your screen growth, and that it as simple as checking it once a day, because the frequency of necessary cleaning relates to what kind of growth you’re getting.

I nice, thick mat of emerald green hair algae does the best filtering.

Regardless of growth type, as the algae mat grows thicker, the outer layers block light (and flow) to the lower layers, specifically where the algae attaches to the screen. This causes weakening of the strands, which can lead to algae detaching from the screen. This is more likely to happen with a single-sided screen, because the light intensity less at the screen level. It is less likely to happen in an enclosed-box 3D growth type system, as the algae is supported a little better.

What really tells the story is what the algae mat looks like when you clean it. If you are regularly cleaning off a thick mat of green algae that is firmly attached to the screen, you can probably let this go for a few more days between cleanings. Increase by one day at a time and monitor closely. If the algae becomes a lot easier to clean off, or becomes straw-like near the screen, this means the algae in the lower layers is not getting enough light and/or flow, and is dying, and you’ve reached (or possibly exceeded) the limit on how long you can go between cleanings.

If you are getting a thin layer of algae, but it’s not too dark (maybe a darker green or thin and brown, and you can still see the screen) you can let the screen grow for a few more days. The key here is that as long as light is penetrating all the way down to the algae attached to the screen, you can let it grow. You want to allow the green algae, however much you are getting, a chance to grow.

If you are getting a little thicker mat of brown growth, don’t go over 7 days. Same goes for the yellow, rubbery growth. You can clean these more frequently than 7 days; try to leave as much green hair algae that you have on the screen. If you are getting black, slimy growth, clean about every 3 days.
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