How to grow zoanthids

Written by chris podbielski
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How to grow zoanthids
Zoanthid (nttrbx, Flickr)

Cousins to swimming jellylike animals of the cnidarian family, zoanthids make easy aquarium additions for amateur to expert reef tank hobbyists. These stationary but colourful polyps, sometimes called "zoas" or "zoos," attach to rocks and colonise, adding a variety of colour to a marine environment. Aside from achieving artistic goals with the animals, zoa cultivators also enjoy trading or selling the polyps for profit.

Skill level:

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Things you need

  • Reef-ready aquarium
  • Sump
  • Protein skimmer
  • VHO, PC or Metal halide lights and timers
  • Heater
  • Live rock
  • Live sand
  • Reverse osmosis water
  • Hydrometer
  • Thermometer
  • Water test kit
  • Powerheads
  • Rubber gloves
  • Eye protection

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  1. 1

    Acquire an aquarium, preferably 65-200 gallons in size with a sump and protein skimmer. Rocks and sand consume too much space in a smaller tank. Additionally, zoanthids need room to colonise and spread quickly when healthy. The sump and skimmer used with large capacity tanks provide additional filtration to control algae. (Many tanks include the sumps on the bottom, hidden within the aquarium cabinet or stand.) The choice between glass and acrylic tanks rests with you---acrylic maintains more even temperatures but scratches easily, while glass does the opposite.

    How to grow zoanthids
    Reefaquarium, Home-Reef, Wikimedia Commons
  2. 2

    Choose a location for your reef tank. Without an aquarium cabinet, you'll need a sturdy table for the weight of the tank, the rock and sand, and all of the water. Keep the tank away from windows, air ducts and radiators to maintain stable temperatures. Consider maintenance and splashing. You want easy access to clean all areas in the aquarium as well as the floor, and to add and retrieve marine life easily. Make sure you select a place where you will enjoy watching your reef thrive.

  3. 3

    Assemble your lighting system and timers. Zoanthids need moderate to bright light for approximately 10 hours per day. Many zoo farmers use actinic and moon lights in addition to the regular system. Because of the hours required and the variety of lights, you may need more than one timer to keep the zoas fed and colourful.

    How to grow zoanthids
    Tower of Aquatic Power, nttrbx, Flickr
  4. 4

    Add a powerhead, heater, and a thermometer. Your zoanthids require water temperatures between 76-84˚F. Cooler and warmer temperatures in your house or office will affect your zoas' colour and health. The powerhead creates current. Your zoas thrive in moderate to high currents, using their tentacles to pull food particulates from the flow.

  5. 5

    Buy Reverse Osmosis (RO) water for your aquarium, commonly found at your Local Fish Store (LFS). Tap water has too many chemicals and the wrong balance of minerals. Most LFSs sell plain RO water or RO pre-mixed with salt. If mixing in the salt yourself, use a hydrometer to get the balance right. Let the mixed water set for at least 24 hours and then retest for temperature and salt content before adding to your aquarium.

  6. 6

    Add the live sand and live rock to the aquarium. Live rock and sand come in sealed packages (from your LFS or online retailers) and contain good algae and bacteria needed for the biological filtration of your reef tank. Pour the sand first (about four inches) and set up the rocks for stability as well as aesthetic value. Create arches and steps, but make sure swimming fish or zoa colony expansion won't knock them over. You'll need at least 0.68kg. of rock per gallon capacity of your tank.

    How to grow zoanthids
    Zoanthid Coral Frag on Rock, smoMashup_, Flickr
  7. 7

    Slowly add the water and test it regularly, before adding any marine life. Test for salinity, alkalinity, ammonia, nitrate, pH and other chemicals or minerals (see "Propagating Zoanthids" in the resources below for specifics). Watch for algae blooms over the next two weeks. When you achieve biological and chemical stability, you're ready for your first zoas.

  8. 8

    Buy your zoas from an LFS with a knowledgeable staff, or get some from a friend willing to provide advice. As you gain experience, you can find more exotic specimens from retailers around the world. Keep in mind, your zoanthid may look completely lifeless at first, displaying closed polyps and little or no colour variation. Fragging (separating the polyps and a sliver of their home rock from the colony) and transportation from one tank to another put zoas in shock.

  9. 9

    Acclimate your zoas to your tank conditions. The Doctors Foster and Smith site (see resources below) describes both the bag float method and the drip-line method in detail. Both methods allow you to slowly add water from your tank to the water your zoanthids came in---slowly reviving the animals so you can place them in your aquarium without compounding the shock symptoms. The zoas will take anywhere from minutes to weeks to bloom again. Some of the polyps may die---do not place these in your clean tank. You can always quarantine your zoas and other marine life in a smaller tank for a week or two if you have one set up.

Tips and warnings

  • Zoanthids feed primarily on particulate matter in the currents and through photosynthesis. Target feeding (with a turkey baster or just sprinkling flake food into the aquarium) a few times per week may encourage zoa growth. Ensure marine additions to your reef are compatible with your zoos. Some corals, snails and fish will help maintain tank cleanliness, while others will attack your zoanthids.
  • Some zoas shoot palytoxin, which may cause blindness or death. Do not handle any zoanthids without rubber gloves and protective eyewear. Wash all tools (scalpels, chisels and hammers, if fragging), towels, containers and other items thoroughly with soap and water after handling the polyps. Also, soap, lotions, and other items for human consumption are toxic to zoas. Make sure your gloves, tools and containers are well-rinsed with plain water before touching the zoanthids.

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