Training Sun Polyps to Stay Open Day and Night


The following is a submission from Laurie, a fellow reef aquarium hobbyist and an avid AquaNerd reader. She contacted us recently and wanted to share her experience with feeding sun corals.

Sun Coral in Mixed Reef Aquarium

I recently ordered a Dendrophylia online and, to my disappointment, ended up with a colony of Tubastrea, which are commonly known as sun polyps or sun corals. I had heard that sun polyps usually open only when the lights are off and will remain closed during the day. My sun polyp colony never seemed to open, day or night, which was very frustrating. I read that newly purchased corals usually don’t get fed for a long time, and in their weakened state sun polyps tend to stay closed. At that point they need nutrition in order to survive and thrive. Since sun polyps are a non-photosynthetic coral, they get their nourishment from food rather than light.

Continue reading to see how I got my sun polyps to open up during the day and stay open longer.

The secret of getting sun polyps to stay open is consistent target-feeding, repetition, and lots of patience. I’ve found that a small 3mm plastic pipette works the best for target-feeding my coral. I cut off just enough of the end of the pipette so that mysis shrimp can be easily moved in and out of the pipette tube. I was able to order one hundred 3ml plastic pipettes online and they’re very inexpensive. To feed, I started by soaking frozen mysis shrimp in Kent Zoe Vitamins, garlic drops, and a little tank water. Before the vitamin soak, I washed my frozen mysis shrimp with RO/DI water to remove any possible phosphates. I then turned off my pumps and powerheads, then target fed a single mysis shrimp into the closed top of each sun coral polyp and continued this process for several weeks.

Sun Coral

When I started, I tried to feed my coral at the same time each day, but then I gradually started feeding them every other day to keep them happy while decreasing the work load. Gradually my sun polyp colony learned to open during the day and stay open – although this process took about one month for them to fully open. Sun polyps are voracious eaters and they love meaty foods. Of course, when you’re heavily feeding your coral be sure to stay on top of your frequent water changes so that you don’t get a build-up of nutrients in your tank. I run a Phosban reactor loaded with a mixture of Nitrate Sponge and Phosban to pull out excess nutrients from my reef tank.

My sun polyp colony is now a favorite coral of mine because the polyps have learned (from repetition and consistency) to open and stay open all day and most of the evening. The vibrant bright orange tentacles of the sun polyp are a beautiful addition to my 65-gallon reef tank, and it’s a good feeling when you see your livestock flourishing from the extra care you give them. I’ve placed the coral in a grotto-like cave of my live rock in the lower third of my tank. They receive lower light and gentle flow, and seem extremely happy there.

Happy reefing-keeping!


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