Zoanthid Care Guide

If you are here looking for general care for zoanthids, please, carry on reading! If you are here looking for a specific question or problem, feel free to skip ahead to Common Zoanthid Problems.

What are Zoanthids

Zoanthids are a small, soft coral that spreads by growing outward from the main colony. Zoas are very colorful and far less picky about water parameters than LPS and SPS corals. Zoas are a variation of palythoa coral with small polyps. Often, these names are used interchangeably describing both zoanthid and palythoa corals. The difference is largly in the size of the coral polyp. Zoanthid polyps are usually the size of a dime or smaller, where pally polyps are typically the size of a dime or larger.

Zoanthid Care - Flow

Zoanthids prefer a moderate amount of flow. Too much flow can make it difficult for polyps to open up, however, they like enough flow to keep detritus and any other waste and buildup away from the coral.

Like many other coral, zoas often react differently depending on flow. If there is more flow, zoas usually have short stalks, where lower flow may result in longer stalks.

Zoanthid Care - Lighting

Zoanthids are photosynthetic coral, however they do not demand nearly as much light as many other corals. For best growth and coloration, blue and actinic color lights are ideal. Aiming for roughly 8 - 10 hours of full light, and 2 - 4 hours of ramping up/down will typically satisfy most corals, including zoanthids.

One indicator of how much light is needed for each different variation of zoanthid seems to be based on their coloration. According to an article by SaltwaterAquariumBlog, the brighter the zoanthid coloration, the more light it needs to thrive.

For more about the different types of lighting, see the Reef Stable Saltwater Aquarium Lighting Guide.

Zoanthid Care - Placement and Aggression

Zoanthids are not an aggressive coral, but placement can drive your success and growth rate. Beyond flow and lighting, zoanthids should be placed on flat surfaces. Zoas grow by spreading outward and struggle to grow on rocks that are too porous. By placing zoas on flat surfaces, you allow these zoanthids to grow more easily, and quickly.

Zoanthid Care - Feeding

According to an article on Chaos Aquaculture, zoanthids enjoy eating specialized coral food, as well as simple foods such as brine shrimp, copepods, and rotifers. Zoanthids also enjoy amino acid and vitamin supplements. However, feeding is not required as zoas are photosynthetic. Therefore, if you are not feeding other coral, it may be best to not worry about feeding zoas.

Zoanthid Care - Temperature

The commonly agreed upon temperature for zoanthids is the same as most corals, averaging at 78 degrees F. Zoanthids can survive in a wide range of temperatures, however 78 is the average. The best bet is to keep the temperature stable, within 1 degree F, for the best results!

Alkalinity, Calcium, and Magnesium

For Zoas, there is very little that needs to be done for alkalinity, calcium, or magnesium levels. Maintaining a stable alkalinity, within about 0.5dKh will be one of the best maintenance routines you can do for nearly all corals. After alkalinity stability, calcium stability within about 25ppm is also valuable for optimal growth. There are no specific values that work best for all zoantid care. It's best to choose a value that is ideal for all corals.

Nitrates and Phosphates

Though you don't want to be absolutely zero on Nitrates or Phosphates, you also don't want to be too high either. The ideal levels for Nitrates is between 1 and 10 ppm. Phosphates should be roughly 0.01-0.05ppm.

The reason for having some nitrate and phosphates in your tank is due to research showing that coral need nutrients to enhance their growth and coloration. Too much of either, however, will slow growth and reduce coloration.

Dirty Water Theory

Many people believe that zoanthid care is best in "dirty" water. That is, high levels of nitrates and phosphates. There is not much evidence to suport these zoanthid care claims. Though it should be noted that zoanthids are very hardy and can handle a wide range of nutrient levels, including dirty water. Because of this, zoas make great beginner corals, and this hardiness is likely the origin of the dirty water theory.

One thing I can say is that zoas generally do not like water with nitrate that is undetectable. I think targeting 3-7ppm of Nitrate would be ideal, but don't try to chase numbers. Instead just try to keep the levels stable.

Thoughts on Zoanthid Care from Marine Depot

Pests and Common Problems

Why are my Zoas Closed / Not Opening?

There are a number of reasons why zoas may not be open. If they are new to your reef tank, it may just be stress. In which case, it could take up to a couple weeks for the zoas to open up.

Another reason zoanthids may not open is because of too much flow. If the flow is too heavy, the zoa may have a hard time opening and stays closed to protect itself.

Finally, there may be something pickin on the coral. Fish including angelfish (large and dwarf) as some inverts including emerald crabs may be nibbling on the coral. Otherwise, there are some common pests that may irritate the zoanthids.

Zoanthid Eating Nudibranch

Zoanthid Eating Nudibranch are small, slug-like creatures that take on the color of the corals they're eating. Learn more about Zoanthid Eating Nudibranchs.

Zoanthid Eating Spider (Sea Spider)

Zoanthid Eating Spiders (Sea Spiders) are small, spider-like creatures that are often found on or near corals or anemones they are eating. Learn more about Zoanthid Eating Spiders (Sea Spider).

Zoanthids are Melting?

Another problem with zoas is when they look like they are melting. Unfortunately, melting zoas typically means they are dying. Things to watch out for include too much light, too much flow, and parameters suddenly changing. Though most people think of this as temperature, salinity, or alkalinity, it could be other parameters such as nitrates as well.

Whenever I carbon dose, specifically vodka dosing, I found that my zoas die and melt away. I am unsure as to if this is due to the drop in nitrates or rise in carbon. Either way, the sudden change in levels caused the zoas to melt away.

Zoanthids are inverted, like an umbrella?

When zoas open too far, they look like an umbrella. They will typically recover from this, however there are a couple of reasons that this may happen. The first is that there may not be enough light. If only one polyp is inverted, I would not adjust the lighting as is may just be a random occurrence.

Another, and one I have personally seen, is a feeding response. When they eat, rather than closing, some zoanthids open more. This is just an oddball occurance and nothing to worry about.

Zoas are spitting brown slime?

Good news! If your zoas have a brown goo or slime coming from their mouths, it is typically nothing to worry about. Much like an anemone, this is usually just the coral's feces, or poop.

Palytoxin

I do have to make a note about palytoxin. Zoanthids and Palys can excreet one of the most deadly toxins known, palytoxin. The worst part, there is no known cure for it. Because of this, you should only handle zoas while wearing gloves, and keep them submerged at all times. This reduces the ability for the toxin to get in the air or your blood stream.

Though not overly common, some reefers have gotten very ill, or even died from this toxin. Many from cleaning pests off the coral / rock with hot water. Allowing this toxin to become airborn. Running activated carbon can help in the removal of the toxin from the water, but is not guaranteed.

As with many other corals and fish, it is VERY important to do research on propper zoanthid care and prevent potential illness.

Zoanthid Care Guide - Cheet Sheet

Temperature

• Zoanthids Prefer to be at roughly 78 degrees F.

Alkalinity

• Focus on stability, maintaining within 0.5 dKh
• Anywhere between 7-12 dKh

Calcium

• Focus on stability, within 25ppm.
• Zoas do not tend to rely on calcium as much. Any values in the safe range should be fine.

Magnesium

• Zoas do not tend to rely on magnesium as much. Any values in the safe range should be fine.

Nitrates and Phosphates

• The below numbers are ideal, but zoanthids can tolerate a wide range of nutrient levels.
• Nitrates: 1-10ppm
• Phosphates: 0.01 - 0.05ppm

Lighting

• Zoas are not overly picky on lighting. Provided the PAR is roughly 100, you should be fine.
• Blue and Actinic spectrum are best for color and growth.

Additional Coral Care Reading:

• Reef Stable - Acropora Care Guide
• Reef Stable - Montipora Care Guide
• Reef Stable - Euphillia Care Guide
• Reef Stable - Zoanthid Care Guide

Conclusion

Zoanthids are one of the easiest, most beautiful, and quickest growing coral! With this fast growth, zoanthids are also typically low cost as well. If you are looking for a good staring coral or just want to fill in the empty, lower light places in your reef tank, zoas are a perfect coral for you! With an infinite number of colors and patterns, you are almost guaranteed to find a zoa that matches you!

See what zoas Reef Stable has in stock!

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About the Author

John Krenzer

John is a Software Engineer with a passion for saltwater aquariums, as well as the founder and president of Reef Stable. He started in the aquarium hobby as a child with a 20 gallon freshwater aquarium. His interest in aquarium life grew and in 2008, John set up his first saltwater aquarium.

Today, John maintains a 120 gallon mixed reef aquarium as well as a 210 gallon aggressive species aquarium. These large tanks are contained within the same system, sharing a sump as a means to reduce total maintenance and increase total water volume.

John writes articles for the blog as a means to learn about more reef aquarium topics. These articles act as a reference for the readers as well as himself. John updates these articles frequently to provide additional information or make corrections as new information becomes available.

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