Corals Gone Wild: Don’t Let Encrusting Polyps Take Over Your Tank!

I have a confession to make. When I mention my 75-gallon “reef tank” in my posts here at Saltwater Smarts, I’m not being entirely truthful in my terminology.

When I first set up the tank almost 14 years ago and over many of the ensuing years, it could accurately be described as a reef system. It contained a nice mix of soft corals and a few large-polyp stony corals to boot.

Today, a better descriptor for the tank might be “Green Star Polyp Paradise” or perhaps “The Green, Green Polyps of Home.” Why? Through my own benign neglect, approximately two-thirds of the tank has now become completely overrun with green star polyps.

Most of the rocks are smothered with the stuff, and the only corals that haven’t yet succumbed to the “Creeping Green Menace” are a gorgonian (though the star polyps are doing their level best to gain a purchase on it), a finger leather coral located at the far left-hand side of the tank, and an open brain coral situated toward the front right-hand side of the tank and more or less out of reach of the star polyps (for the moment).

Oh, and did I mention much of the tank’s back pane is covered with pulsing Xenia? Yep, I let that get away from me, too.

With so much real estate dominated by the star polyps and pulse corals, the aquascape in the system just isn’t all that appealing to me anymore. I want a variety of interesting corals to enjoy—not a monochromatic, monospecific mess. But, alas, there it is!

Salty citizens, hear me out! This could happen to you! (And if you can identify the origin of that saying, you’re at least as old and nerdy as I am.) However, it’s not a foregone conclusion if you take the following steps to keep rapid-spreading, encrusting corals (star polyps, pulsing Xenia, colonial zoanthids, and the like) in check:

Exclude ‘em

Obviously, the best way to prevent fast-spreading corals from taking over your tank is to avoid introducing them in the first place. But keep in mind that knowing which species are apt to do this takes a bit of prior research, especially if you’re new to reefkeeping and buying your first corals. Don’t just purchase an assortment of nice-looking specimens and hope for the best.

Also, be aware that green star polyps and other fast-growing species are commonly (and justifiably) sold as part of “beginner coral packs” featured by various vendors. If you choose to purchase such an assemblage, be sure to verify all of the species in it and research their needs and growth habits.

Isolate ‘em

Green star polyps and other encrusting corals will rapidly grow onto any adjacent rocks, glass, acrylic, or other hard surfaces—in some cases, as mentioned above, even onto and over other coral species. To keep these corals from growing where you don’t want them, it’s helpful to position them at least several inches away from other rocks or corals. They’ll still spread outward from the rock they’re growing on and likely down onto the substrate, but it’s a lot easier to cut and detach them from loose substrate than from irregular-contoured rocks.

If the coral grows up onto the sides of the tank and you don’t want it there, the encrusting tissue/polyps can simply be scraped off with a razor blade (or an acrylic-friendly alternative)—which finally brings us to…

Propagate ‘em

Polyps or tissue mats pruned away from the larger colony or scraped off the glass/acrylic can usually be attached to small rocks or rubble (via rubber bands or aquarium-safe cyanoacrylate gel) with little difficulty. Or, you can place them loose in a rubble tray and wait for them to attach to pieces of rubble naturally. Your local aquarium store may be willing to take these frags off your hands in exchange for cash or store credit.

What’s your technique?
If you’ve got green star polyps or a similar weed-like coral in your tank, what’s your secret for keeping its growth in check? Let us know in the comment section below.

Photo Credits: Brett Levin, Tim Sheerman-Chase