Don’t Get Burned by Flame Scallops!

Flame scallops prefer recesses with subdued lightingMention beautiful bivalves for the marine aquarium, and the various tridacnid clams (the so-called giant clams) will probably come to mind. Likely, the flame scallops of the genus Ctenoides will too. However, while the tridacnids have a fairly decent survival record in captivity if given proper care and a suitable environment, the flame scallops usually fare dismally in aquariums.

The two usual suspects

Based strictly on my personal observations, the two flame scallops you’re most likely to come across in the aquarium trade are C. Scaber (formerly Lima scabra), found in the Caribbean, and C. ales (formerly Lima ales), also known as the electric or disco flame scallop, from the Indo-Pacific.

They range between 3 and 4 inches in diameter and have white shells and red to orange-red tissues. They also have long, tapering red, or sometimes white, tentacles extending from the mantle. C. ales gets the “electric” or “disco” moniker from the fascinating flashing display it produces on its mantle lip, which looks rather like flickering electricity.

Interestingly, a recent study published in the Journal of the Royal Society (read the report) has revealed that C. ales achieves this flashing effect not via bioluminescence, as once thought, but by reflecting light with tiny silica spheres.

So why shouldn’t I keep one?

Flame scallops are azooxanthellateThese bivalves present a few significant challenges with respect to aquarium keeping. Chief among them are their dietary requirements. Unlike the tridacnid clams and most of the corals we keep in reef systems, the flame scallops are azooxanthellate, meaning they don’t have photosynthetic zooxanthellae in their tissues to help sustain them. Instead, they must get all the nutrition they need from filter-feeding on plankton of very small particle size, e.g., phytoplankton and invertebrate larvae.

Aye, there’s the rub! Even a very mature reef system with a productive refugium attached is unlikely to provide enough plankton to sustain these creatures, so you have to routinely introduce significant quantities of plankton of a suitable particle size to the tank—either by target feeding or flooding the system with enough plankton to produce a sufficient concentration in the water column.

As you can imagine, this feeding approach can quickly foul the tank. What’s more, it’s very difficult to determine whether the scallop is actually ingesting the plankton offered—not to mention getting enough nutrition from the food assuming it is actually ingesting it. The harsh reality is that most specimens starve to death within a matter of months in captivity.

Another issue with these bivalves is that they tend to favor hidden recesses and more subdued lighting. Couple that with their ability to swim (albeit not particularly gracefully) by clapping their shells open and closed, and it shouldn’t be surprising that specimens kept in aquariums often “wander” into regions of the tank where it’s difficult to reach or see them, further complicating feeding.

The bottom line? Despite their gorgeous looks and usually very modest price tag, the flame scallops are best left to very dedicated, expert hobbyists—or better yet, left in the ocean.

Photo credit: fergusfleming, Jamie Henderson

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About Jeff Kurtz

Jeff Kurtz is the Co-founder/Editor of Saltwater Smarts, former Senior Consulting Editor for Tropical Fish Hobbyist Magazine, and the aquarist formerly known as “The Salt Creep.” He has been an aquarium hobbyist for over 30 years and is an avid scuba diver.

Comments

  1. Jay Hemdal says:

    Funny that the “disco scallop” was just recently identified as reflecting light, and not generating it through bioluminescence. When I first saw one 15 years ago, I was curious about the “lights” – but simply turning off the tank lights soon showed me the animal itself wasn’t generating the light (grin). Flame scallops recently made my list of “top five species, commonly sold, that people need to avoid”.

    • That’s an excellent point, Jay! If bioluminescence were behind the disco scallop’s “light display,” it certainly ought to be more evident in the dark. Thanks for sharing!

  2. Paul Baldassano says:

    Scallops are great……To eat. Eat them or leave them in the sea unless you want to feed them 24/7. So if you have a girlfriend, and want to keep her, don’t buy a scallop

  3. You mention phytoplankton as “very small, particle size” exactly what size and should I also add zooplankton?

    • Jeff Kurtz says:

      Hi Tohni! This article by Rob Toonen, though several years old now, includes some very good information on feeding these animals and other challenges associated with keeping them: http://www.advancedaquarist.com/2002/7/inverts. In it, he writes that “the majority of food by weight in the gut of flame scallops I collected from the wild appeared to be phytoplankton in the range of 5-40 micrometers.”

  4. My local LFS tricked me into believing these were self sustaining, feeding on fish waste. I have now had mine for a little over a month and would like a recommendation on what to feed it, I have seen phytoplankton for sale at Petco. Also if i try and spot feed how much should I try at a time? I no longer trust that LFS

    • Jeff Kurtz says:

      Hi Chris! I would be inclined to return the flame scallop to the LFS (assuming they’ll take it back), who definitely misinformed you on its nutritional needs. Also, if you haven’t done so already, you might want to check out the article by Rob Toonen that I recommended to Tohni above. Here’s a link: http://www.advancedaquarist.com/2002/7/inverts. I think you’ll find it very informative with respect to the feeding requirements of these animals.

  5. Anthony Braunstein says:

    Hello there I have had one of these things for almost two years. The maintenance is very easy actually. As long as you keep up with your tank. Every other day I target feed mine 3ml of zooplankton and it is loving life in my tank.

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