Table of Contents
Sea spiders, by definition, are species called pycnogonids, which are marine arthropods. They are quite common predators inhabiting zoanthid corals. There are over 1300 known species of Pycnogonida, some of which are so small, only 0.04 inches in diameter, that they are difficult to notice. They are adept at hiding inside the polyp and adapting to changing conditions. Pycnogonids are known to feast on zoanthids, anemones, or sponges.
How do they get to our aquarium?
Mostly when buying new corals. They’re usually hidden on the coral’s base where we can’t see them. When we unintentionally bring them into the ecosystem, they’re often in the form of larvae or freshly laid eggs. That’s why it’s so important to quarantine them in a separate tank before placing the coral in its final destination.
How to recognize them?
They usually have eight legs, but they can have appendages that might be mistaken for legs. These appendages are used for caring for the young. The average size of an average sea spider is about 5 mm in diameter. Due to its ability to adapt to the environment and hide inside the polyp when it’s closed, it’s often difficult to see them. Sometimes, only when they extend their legs outside the polyp, can we see exactly where they are.
Do zoanthids get sick and how to treat them?
As Zoanthids grow, they form a colony made up of independent polyps. It’s within these polyps that sea spiders hide.
Like all organisms, Zoanthids can face issues maintaining a healthy form. Poor conditions such as changes in salinity, inadequate circulation, or weak lighting can weaken Zoanthids. But the main problem often lies with sea spiders that parasitize them.
Because sea spiders usually hide well under a layer of mucus, most treatments remain ineffective against them. They often hide at the base of the polyps, so it’s worth checking there too. One can try dipping the coral in a solution to remove the parasites. When introducing a new colony into the aquarium, it’s advisable to try to clean it of visible sea spiders and their eggs as much as possible. It’s also worth quarantining the colony to protect other corals from pests.
Specialized, dedicated treatments applied regularly every three weeks or more can help remove remaining or freshly hatched sea spiders. Also, natural predators such as the six-line wrasse and the melanurus wrasse are known for their interest in sea spiders. Additionally, Coris wrasse and Butterfly Fish can also help remove pests from corals.
The best method is physically removing the parasites using tweezers. If possible and visible, it’s worth removing laid eggs during cleaning and then dipping the coral.
When choosing treatments to remove parasites, make sure they don’t contain oxidants and only act actively on pests. Use the treatment as a liquid to support the quarantine process for new corals.
Summary
Finally, if unsure whether Zoanthids have a problem or if what is seen are indeed sea spiders attacking Zoanthids, try taking photos and identifying them using Google or posting them on Social Reef.
About the author
Marek Protasewicz
Reefkeeping has been my passion for over 10 years now. I love learning. The hobby has taught me many valuable lessons, patience being the best example. Combining work and passion is my path. I run Crazy Coral, a marine aquarium shop, for a number of years. Building this business from the scratch I learnt from my own mistakes at a heavy cost.
Later I managed a project aimed at development of methods for quick growth of Corals in non-natural conditions. The project was carried out by Get Sales, Poland. Presently, I am responsible for distribution strategy at Reef Factory, of which I am a co-founder. The company produces smart devices for marine aquaristics. The last projects I have been involved in are Social Reef and ReefPedia.
My social media profiles
