Oddball Reef System Symbiosis

Symbiotic relationships are among the most interesting aspects of this hobby. A coral reef is a battlefield for real estate; however, there are still amazing examples of cooperation between completely different animals. Everyone is very familiar with clownfish and anemones, and for good reason! This combination is likely responsible for drawing more people into the hobby than anything else. This article, however, looks at some less common partnerships.

Hermit crabs and coral

Hermit crabs of the genus Paguritta are definitely oddballs. When aquarists typically imagine a hermit crab, it’s a crab living in a shell and motoring around the tank looking for algae and bits of food to scavenge. However, these little guys live in colonies of Astreopora and spend their whole lives in their burrow. Having said that, I’ve seen them in other corals when they are collected from different regions. For example, the yellow crabs in the video are from Australia, but I’ve seen blue ones from Fiji that were living in Platygyra.

Burrowing hermit crabs of the genus Paguritta

Burrowing hermit crabs of the genus Paguritta

When these hermit crabs first came onto the reef aquarium scene, there really wasn’t a care guide to follow, so we had to try our best to keep them alive. We have found that they filter feed mainly and seem to really like small meaty foods such as rotifers. They seem to do better with heavy feeding, but it’s important to not overfeed and pollute the tank because the food they consume is not likely to be quickly consumed by fish or other inhabitants.

Sexy shrimp and mini carpet anemones

There are actually many types of shrimp that develop symbiotic relationships with both corals and anemones, but the sexy shrimp are my personal favorites because they are not nearly as reclusive as some of the other inverts. That is actually one of the things that kept some really cool symbiotic relationships off my list. Boxer crabs, for example, hold a small anemone in each claw, but these critters often hide so much that I never can get a shot of them. It’s hard for them to make my favorite list when I never see them!

Sexy shrimp are active and easy to care for, making for a great oddball choice

Sexy shrimp are active and easy to care for, making for a great oddball choice

The other nice thing about the anemone and shrimp pairing is that they are very easy to care for. The anemones themselves are very tough and don’t move around as much as some other types of anemones such as bubble tips, which are likely to run laps around your tank. The shrimp are active and can take care of themselves, so you don’t have to go out of your way to feed them.

Sexy shrimp will host in any number of things, not just carpet anemones.

Bisma worm rocks

These feather duster worms are colorful and grow inside colonies of corals, such as Porites and Cyphastrea. These worms bring a lot of interest and motion to what would otherwise be a motionless coral. As you can probably guess, they are filter feeders. I often get asked if they reproduce and increase in number over time. Unfortunately I don’t have a good answer. I can tell that the tubes grow in lengthen over time, but I can’t tell whether the individual count goes up.

Bisma worm rocks

Walking Dendros

Sticking with the worm theme, the walking “Dendro” is a really subtle oddball. I have to put Dendro in quotes because this coral is not a Dendrophyllia at all. It’s actually a photosynthetic coral called a Heteropsammia. The thing that makes it interesting is that it serves as a host to a peanut worm that lives at its base. Unfortunately, peanut worms are super reclusive and not likely to be openly seen. Despite the worm’s shyness, the interaction with the coral is interesting because it drags the coral around the substrate with it. Each day you can expect this coral to be in a different location on the substrate as the peanut worm scoots around.

The walking dendro isn't a Dendrophyllia at all

The walking dendro isn’t a Dendrophyllia at all

Although the coral is photosynthetic and can get most of its nutrition from light, the walking Dendro is a capable predator and can gobble up food if offered either meaty frozen foods or coral pellet food.

Yasha goby and pistol shrimp

The last oddball symbiotic relationship on this list is the partnership between the yasha goby and a pistol shrimp. I love that the fish acts as a lookout for the shrimp that is nearly blind while the shrimp tends to a burrow it makes for both of them. The shrimp almost always has one antennae on the goby as a means of communication.

The nearly blind shrimp tends to the burrow while the goby stands guard

The nearly blind shrimp tends to the burrow while the goby stands guard

I also like how they have matching red and white stripes. Anything that is a striking red and white is not particularly common in this hobby. Off the top of my head, I can think of only two other things—a peppermint Bodianus hogfish and a peppermint angel, which is almost never seen in the hobby.

At first these two were super reclusive, but over time the fish came out more and more, and now it’s out almost all the time. The shrimp isn’t out much, but if you are patient, it makes an appearance once in a while.

What’s your favorite oddball symbiotic relationship?
As I mentioned, symbiotic relationships are among the most interesting aspects of our hobby. Now you know my personal favorite oddball examples. What are yours?


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About Than Thein

Than Thein is the owner of Tidal Gardens and Advanced Reef Aquarium. Than's love for all things underwater began early on when dogs and cats were strictly off limits, but a fish tank? Sure! What started with a 10-gallon goldfish tank eventually turned into a 5,000-gallon greenhouse coral propagation system. In addition to coral aquaculture, Than's other hobbies include scuba diving and underwater photography and videography.

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