What's That Orange Gumdrop?

Orange Gumdrop Nudibranchs, aren't. Sorry. It looks like a Nudi, acts a lot like a Nudi, and it's reasonably closely related to Nudis, but it's actually a Pleurobranch (so it's a sea slug). Pleurobranchs have a single feathery gill that is tucked under a flap (or mantle) where Nudibranchs have naked gills, (which is what their name actually means) openly exposed on their backs, often forming a rosette around their back end. In addition, Nudibranchs don't have a shell, and Pleurobranchs often have a thin remnant of a shell, usually internally, just like the Gumdrop we're talking about today.

That all being said, we're still calling it a Nudibranch, because that's what everyone commonly calls it. Really, for your purposes as a hobbyist, it doesn't change anything. These are really beautiful critters that require specialized care and conditions. Gumdrop's are well named. They look like, well, a very soft gumdrop. Sometimes they're a pale yellowish, sometimes they're nearly burnt orange / red, mostly they come in some cool variation on orange. Their backs are covered with little white spots that are actually glands with which they can excrete a bad tasting chemical as a defense against predators, but they're also quite pretty.

Pleurobranchs, like Nudibranchs, often have very specific diets, and most of them eat either a single sponge or a coral of some type. Gumdrops are somewhat more omnivorous, though they require certain foods. This has bearing on not only what you feed them, but also the type of display they need. You should be prepared to offer Gumdrops live sponge material. In the wild, they've also been documented eating corals from the Leptastrea, Tubastrea and Porites genus. You will either need to supply these as food or expect them to get consumed against your wishes. Some hobbyists also report that they will eat detritus (the slug, not the hobbyist).

While a Gumdrop Nudibranch does not need much space, they need nearly impeccable stability and so we recommend keeping them in aquariums that are at least 40 gallons. Aquariums that are smaller than this are very difficult to keep stable enough for the Slug, but also for the sponges the slug needs. Filtration should be strong, but flow should be gentle and diffuse, Slugs do not do well in strong, direct flow. So, pay special attention to the filter return. As pH stability is also at a premium, having an off schedule refugium (refugium lights are on, when tank lights are off and vice versa) can really help balance out day and night fluctuations in pH and it will also help keep your nitrates under 1-2ppm which is the highest we'd recommend for keeping any Nudis long term. Lighting is largely immaterial, but any Sea Slug or Nudibranch should be acclimated to high intensity lighting slowly.

Water chemistry also needs to be stable, and this starts with regular water changes and quality salt. Our entire system runs on Tropic Marin, and yours should too. We find it to be the most consistent, highest quality salt available today. They've been leading the way on salt mix consistency and quality for decades. This is exactly what you're looking for when you are keeping delicate species like Gumdrops. You don't want to do a water change and dramatically alter your system's pH, or dkh, etc. Regular water changes replenish the buffers and minerals that get used up through the biological processes in your aquarium and filter. They're also the most valuable tool in your quest to export nutrients. Do not skip change day (it's like leg day, but lighter).

What else can you keep in a gumdrop display? You can keep a variety of corals and fish, though you want to make sure you don't keep anything that you don't want your gumdrop to eat, and you also need to avoid things that will pick on the gumdrop. You want the most peaceful of fish. Things like Firefish, and Cardinals make excellent choices. Aquacultured Seahorses (like an Orange Reidi or five) might also make for a very interesting display. Make sure you add the fish first and allow the system to biologically adjust for them before adding the Seaslugs. Nudibranchs (and Pleurobranchs) dislike nutrient spikes.

As you've maybe noticed, gumdrops aren't the easiest animals to keep. This isn't something you just casually drop in your brand-new reef tank because you think it's cool. That being said, they are cool! They just need some more forethought in keeping than some other marine critters do. If you've been keeping aquariums for a while and you have a display that is super stable and ready for something like this, then maybe give a Gumdrop Nudibranch a try. Ask your LFS about Berthellina citrina from Quality Marine today!