Many a beginning marine aquarist has noticed upon setting up their first aquarium a vibrant purple blanket beginning to overtake their new setup. It starts off as little purple patches on your live rock and eventually overtakes most of your live rock surface. You may start to worry that your water quality is off, or that you need to do something to get rid of this purple blanket, but fear not - these algae are your friends.
Called coralline algae, these algae share the same characteristics as "nuisance"” algae: they are a highly adaptable photosynthetic organism, and as most aquarists know, often tough to eliminate. But unlike the many harmful types of algae often found in the aquarium, coralline algae are beneficial.
a friendly advantage
Coralline algae often hitchhike from the ocean on your live rock, and then grow on any solid or porous surface, including the glass of your aquarium. They are found in two forms: an articulated type that resembles tree branches growing from the substrate, and the more commonly seen non-articulated blanket form that grows on live rocks and on top of substrate. Coralline algae can grow fast and overtake a lot of live rock surface to keep other harmful algae at bay. It also produces magnesium, beneficial to the health of your herbivore inhabitants.
If you are starting a new saltwater aquarium and want to transfer some of your beneficial coralline algae to the new setup, simply scrape some of it off and transfer it to the cured live rock. To ensure growth, keep calcium concentrations near 420 mg/L and maintain carbonate hardness above 8 dKH, and consider products such as
Purple Up, designed to promote the growth of coralline algae.