Coralline Algae

Coralline algae deserves special mention. Coralline comes in beautiful shades of pink, purple, red, lime green and lavender and are commonly found in the aquarium hobby as an encrusting variety as well as the rarer ‘plating’  and ‘scrolling’ varieties. No wonder coralline algae is so sought after by aquarists who don’t have enough of it.

A genus of hard, calcified algae, coralline algae is beneficial to the aquarium in that nuisance hair algae is less likely to take root where there is coralline growth. Also, coralline adds a colorful new dimension to otherwise boring-looking grey live rock!

How To Grow Coralline Algae

When conditions are ideal coralline algae grows rapidly over live rock, aquarium glass, powerheads and even the shells of snails and hermit crabs.

Coralline algae thrives in conditions similar to that of stony LPS and SPS corals — low nitrates, and good pH, alkalinity and calcium levels. A stable pH above 8.0, alkalinity at 8 to 12dKh and a calcium level of 400mg/l will give ideal conditions for coralline growth.

Coralline Algae And Direct Light

Coralline algae tends to not grow where the aquarium lights are too strong, such as on the top of rockwork. Under metal halide lights, for example, you will find coralline growing in the more shaded recesses of the aquarium. Coralline seems to benefit more from aquarium lights in the blue to actinic spectrums.

coralline algae

Plating coralline algae on live rock rubble

Coralline algae seems to prefer more subdued lighting since many species found in the saltwater aquarium hobby are actually from deeper waters. If you place a coralline encrusted piece of live rock under direct light, the coralline will bleach and turn white within a week — something to think about when arranging your live rock.

Seeding An Aquarium With Coralline Algae

Before coralline algae can have a foothold, the aquarium must be ‘seeded’.

If you have obtained a few pieces of cured live rock that are coralline encrusted, they should be enough to seed the aquarium.

Fortunately, this is quite easily done.

Simply remove a piece of coralline encrusted rock from the tank and scrape some of the coralline algae off with a knife. The coralline will come off as fine pink particles, forming a slight paste.  Collect the scrapings in a small cup of aquarium water — the coralline particles should turn the water a light shade of pink!

Use this coralline algae mixture to seed all four corners of the tank. The powerheads should ensure that the coralline is evenly dispersed.

Once a tank is seeded in this way, coralline algae will appear as small spots on the aquarium glass in a matter of weeks.

If there is no coralline algae to be found on your live rock, then the tank can be seeded with scrapings of coralline from another established aquarium.

Coralline Algae And Cycling

If yours is a new aquarium that you are just starting up, do the seeding method mentioned above after the aquarium has finished cycling at the end of 12 weeks. Coralline will die off in the presence of ammonia and nitrite.

If you cycled your tank with a few pieces of coralline encrusted rock, coralline algae may appear on its own once the tank has completely cycled. This is a joyous moment, especially for aquarists who have just endured 12 weeks of aquarium cycling, as it indicates that the tank is now fully cycled and maturing nicely. Coralline will proliferate in a matter of months, provided that conditions are right.

Promoting Coralline Algae Growth

Once coralline algae has gained a foothold in your tank, maintaining ideal water parameters will ensure its continued growth. But if you really want your coralline to explode over every inch of your live rock and tank walls, Seachem’s Reef Advantage Calcium seems to really do the trick!

Reef Advantage Calcium is primarily calcium gluconate — sugar-based calcium — that coralline algae seems to do really well on.  As always, follow the manufacturer’s instructions and avoid overdosing.


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