How to Grow Coralline Algae In Your Aquarium: The Simple Truth

Growing coralline algae is one of the most discussed topics among reef aquarists. When you look online you will find dozens of “secret formulas”, special techniques, tricks and tips for getting coralline algae to grow in a reef tank. Many aquarists try one method after another and never achieve the results they’re looking for. But, here’s some good news. There’s no magic formulas or aquatic voodoo, growing coralline algae is quite easy and here’s what you need to know.

Marine biologists refer to coralline algae as crustose coralline algae or CCA for short. Although the algae appear purple and pink (and sometimes red), coralline algae is simply a form of red marine calcified algae.

Coralline algae are different than most other types of algae you find in reef tanks because the cells of coralline algae form a honeycomb structure of calcium carbonate similar to a stony coral skeleton, only stronger. As the algae grows, it lays down layer upon layer of this super-strong limestone honeycomb. It will strengthen wild reefs with these layers of calcium carbonate. Bonding together the rocks and coral skeletons helps the reef withstand tide surges, pounding waves and tropical monsoons.

Photo by Maggie D. Johnson, Scripps Institution of Oceanography

There are many species of coralline algae. Some species grow in deep, dimly-lit water, while other species grow near the water’s surface in well-lit conditions. Some can grow in a branching formation, some can be thick and plating, but for the most part, the CCA we desire is encrusting.

The coralline alga Mastophora rosea, Fiji By dkeats

There are many reasons people desire coralline algae to grow in their reef tank.

• Coralline algae are often used as an indicator organism. That means if you have CCA growth, your lighting and water chemistry conditions are good enough for keeping stony corals.
• Coralline algae can tie together live rock and coral frags, just like it does on wild reefs, helping to create a more stable aquascape inside your tank. This keeps your frags in place.
• Nuisance algae have a difficult time attaching to coralline algae. This means CCA-covered rocks rarely have any unsightly nuisance algae.
• Corals and other inverts prefer to attach to coralline algae-encrusted rock.
• Finally the most popular reason people desire Coralline algae is that it adds beautiful shades of purple, pink and even red to otherwise drab-looking rock.

Photo by slivacki at Reef2Reef

There is one drawback to Coralline algae that you really can't avoid. CCA does not discriminate where it will grow. It will cover glass, acrylic, and your rocks once it starts to grow. It will also cover your pumps and other equipment, reducing flow rates as it covers the various components of your equipment. Coralline algae is one of the main reasons it is important to soak and clean your pumps regularly in an acidic pump cleaner or vinegar bath. While I would not say CCA is difficult to remove, I would say it is tedious and time consuming.

Photo by Robert at Marine Depot

Coralline algae thrive in the same basic lighting and water conditions as reef-building stony corals. If your aquarium is set-up and being maintained to support stony coral growth, you can grow CCA. The only other thing you need to do is SEED the tank with live coralline algae to get it started. CCA reproduce by spores, one of the most efficient ways possible. The spores will settle on the rock and form new coralline algae colonies and so you only need to seed your aquarium with spores one-time.

CCA spores seem to be found in or on almost all wild reef organisms so it is not difficult for the spores to find their way into your tank with no extra effort. All you need to do is stock the tank with typical reef tank inhabitants. There are, however, a number of ways to intentionally introduce coralline algae which is especially useful when the tank is built using dry or synthetic rock which is certainly becoming the norm over the live rock of days past.

Using live rock rubble is certainly better than larger pieces of live rock because you will run less of a risk of nasty hitchhikers getting into your system. Frags are also another terrific way to introduce live coralline algae to the tank. The CCA growing on frag plugs and mounts will work just fine. You can also add a cleaner snail or hermit crab shell that is encrusted with CCA. Scraping live coralline from a friend’s reef and adding it to your tank is yet another successful way to seed your tank. Essentially just find something with living coralline algae on it and put it in your tank.

There are a few manufactured aquarium products designed to seed your tank with CCA algae. The reviews are mixed and we have yet to test them here at Marine Depot. If you have experience with something like this, we would love to hear about it.

The key to success with coralline algae...the biggest “secret to success”…the thing many reefers miss…is patience!

The ability to leave things alone is very difficult for many of us reef enthusiasts. We’re always tinkering, watching our reef, looking for coral growth and watching for any signs of imbalance or foreign invader. Coralline algae often grows very slowly in a new reef. Don’t be discouraged by stories and photos from a guy whose reef is a month old and covered with CCA. This is rare and not the norm. Just be patient! When you seed coralline algae in a tank with the right conditions, coralline algae will grow. It’s a simple formula, but it takes time. You will first notice little white spots start to appear on various surfaces inside your tank. By the time they are about ¼” in diameter they will begin to take on color and satisfy your CCA cravings.

There are additives that will help coralline algae to thrive but before you add anything, make sure the aquarium has adequate lighting, calcium, alkalinity and water movement. Coralline algae need the same basic aquarium conditions as stony corals. Make sure these conditions are provided before turning to specialty coralline supplements.

Coralline algae use calcium, strontium, magnesium, iodine and carbonates to build their limestone structure. Products like Caribsea Purple-Up, Continuum Aquatics Coralline Purple-CX and others, provide a mixture of these essential elements formulated to stimulate CCA growth with the added benefit of stimulating coral growth as well. On that note, be sure to test your tanks parameters to ensure you are not overdosing any of these elements, especially if you already have a regular dosing regime.

Likely you will already be maintaining the major elements of calcium, alkalinity and magnesium so if you notice that your coralline algae growth slows or stalls, it is likely a minor or trace element deficiency. Elevated phosphates can interfere with the calcification process as well so be sure that your maintaining a low phosphate level.

Too many of you this might sound quite familiar and is really no different than your regular reef tank water chemistry requirements. In conclusion, years of reef aquarium observation have led us to a few key factors to successful coralline algae growth. A stable environment is key for CCA growth, be sure to seed your aquarium with some form of live CCA, when coralline growth stalls, additives can jump-start growth again and finally patience, coralline algae takes time to grow and spread throughout an aquarium.