Another year,  Another additive.

There have been many algaecides available over the years for freshwater aquariums, but this is the first time in recent memory that a marine-specific aquarium algaecide has become available and so heavily promoted.

The product is called AlgaeFix®  Marine, manufactured by Aquarium Pharmaceuticals, Inc. The label claims it will control green algae, slime algae, brown algae, and filamentous (hair) algae. It is marketed as a reef-safe product harmless to fish, corals, and invertebrates, without the usual soft invertebrate exceptions found in the fine print.

I decided to put this product to the test. I had a great candidate for testing, a 100 gallon FOWLR tank with some awesome growth of Debersia, Bryopsis, and other unknown strains of green hair algae. This tank also has a copious amount of red cyanobacteria covering the rock work and substrate. The livestock includes the usual cleanup crew (snails, hermits, urchins) a few rocks with various zoanthids, and a variety of marine fish including a Blue Tang (Paracanthurus hepatus), Deepwater Anthais (Pseudanthias pleurotaenia), Marine Comet (Calloplesiops altivelis), Singapore Angel (Chaetodontoplus mesoleucus), Pajama Cardinals (Sphaeramia nematoptera) and Perc Clowns (Amphiprion percula).

Before I dumped in my first dose, I wanted to know what’s in this stuff. To my surprise, I discovered the active ingredient was not a broad spectrum herbicide but a biocide called dimethyliminoethylene dichloride. After a little digging, I found that it is manufactured by Buckman Laboratories of Canada under the brand  name Busan® 77. This is an industrial liquid biocide use to kill algae in everything from commercial swimming pools, hot tubs, decorative fountains, swamp coolers, and air wash systems.  Busan® 77 is sold at a concentration of 60%, while AlgaeFix® is at 4.5%. So it appears to be a watered down version of the same compound. It is not approved for use in potable water. To be fair though, this just means that the manufacturer hasn’t gone through the testing to satisfy EPA regulations.

Now all this sounds very nasty, but many compounds act differently at different doses. For example, arsenic is present in natural seawater and believed to be beneficial at its natural concentration. All compounds, synthetic or otherwise break down over time and become inert. Some do this in a matter of minutes, while others may take months or years. API claims that Algaefix® does so in 24 hours.

There are two versions of Algaefix® on the shelves. One for freshwater and one marine. Both products are identical sans the labeling. So if your retailer charges more for one or the other, choose the lowest price version.

I prepared the test aquarium so the product had a fighting chance without external influences. I physically removed as much algae as I could, performed large water changes, added a phosphate remover, and got both phosphates and nitrates to undetectable levels on two different brands of hobby-grade test kits (Elos and Seachem).  I gave it a week to settle down before the first dose. The directions make no mention of turning off protein skimmers/UV/ozone or removing activated carbon, so I left the protein skimmer running, the UV bulb burning, and the carbon in the sump.

The label dosage is 1mL per 10 US gallons, dosed every third day.  It doesn’t say how long to do this,  just “until algae is controlled”. After the first week, I saw no changes. In fact, the hair algae continued to grow. The second week was the same. After 7 doses (3 weeks) there was still no effect on either the hair algae or the cyano.

I decided to up the ante and dose 1.5mL per 10 US gallons every other day, effectively doubling the dosage.  After a week of this, the only visible change was that the hair algae was either not growing anymore or growing at a slower pace.

During the middle of the next week, I began to see small tufts of hair algae floating around the tank, heading off and gathering on the overflow grille. I reached into the tank and pulled on some hair algae. To my surprise, it came off very easily.  Everyone knows how tough hair algae attaches to objects, well I could almost peel it off the live rock in mats. Interestingly, the algae was still green as ever but had no holding power. I really expected to see a bleaching event similar to “macroalgae going asexual”, but this never happened. While the algae was weak, I found this to be the perfect opportunity to perform a water change and siphon off all that I could. I probably removed over half of the hair algae in the tank just by rubbing the end of the siphon hose lightly over the live rock.

On the negative side, the few cyano patches that were present before dosing had grown. In fact, the red cyano was taking over. I don’t necessarily blame Algaefix® for this. In all likelihood, a huge increase in DOCs was probably occurring and the skimmer + carbon couldn’t keep up. Although I did see some increased skimmer production, it wasn’t the “cup runneth over” scenario you get when dosing AZNO3. Nevertheless, the product does claim to control slime algae and I saw just opposite.

I stopped dosing at the end of the week and performed another water change. This time I was able to remove nearly all the hair algae in the tank. I left a few tufts behind as food for the urchin. I saw no ill effects in either the fish or inverts in the tank. I was particularly concerned with the urchin’s health as this creature was actively eating the hair algae during the peak of my double dose treatment. It’s been several weeks now and the urchin still looks healthy and active as ever. The red cyanobacteria bloom subsided on its own, with a little help via a thorough skimmer cleaning and regular water changes. I did experience an alkalinity drop ( from 2.8 meq/l to 2.0 meq/l) during the treatment and a subsequent ph drop from a daily average of 7.92 to 7.84.  A little carbonate buffer added during the treatment brought these levels back up.

In conclusion, I find that this product to be very effective on hair algae, providing the aquarist perform physical removal during the treatment period. It does nothing for red cyanobacteria, and may actually make it worse during treatment. Keep in mind that the test aquarium did not contain any SPS or LPS corals, so I can’t comment on the effects of the product in this regard. I also experienced a higher than normal carbonate depletion, so I advise to monitor and correct alkalinity accordingly during treatment.

The labeling states a maintenance dose of 1.0mL per 10 US gallons weekly, once algae is under control. I did not have time to test this. Perhaps this will become the topic of a follow up entry in my blog.