Photobombing Crabs of the Reef

I take a lot of aquarium photographs, both for myself and to share on the blog and social media. When I can, I take the time to frame the shots to minimize the need for edits–and when I can’t, I often crop the photographs for best effect.

When you spend enough time photographing a subject, you notice certain patterns–some the result of photographer’s bias (for example, my tendency to photograph Magellan more than the other seahorses on the reef) and some that emerge from the subject itself.

16B15 Lazarus (Young)

Among the curious things I’ve noticed: crabs are highly capable photobombers.  An unusually high percentage of photographs have at least one crab in the frame, and though that’s partly due to the number of crabs in my aquarium (the total hovers somewhere between 20 and 30), it also reflects the crabs’ nomadic, scavenging tendencies. 

In short, crabs want to be where the action is–and by “action” I mean food.

At the moment, I have three different species of crabs on the reef:

A single Halloween hermit (we call him Lazarus):

16B15 Lazarus Climbing

Three porcelain crabs (the pictured one is my oldest female, Ripley):

16B15 Elvis and Ripley

And somewhere around two dozen red-legged hermits, including one albino (who, unfortunately, I couldn’t find for a photo before I wrote this post).

16B15 Blastomussa and crab

Crabs, and hermits particularly, fill an important role in the reef environment. Reefkeepers often refer to them as part of the clean-up crew (“CUC” for short). As opportunistic omnivores, crabs scour the tank eating everything from algae to leftover food and even poo (disgusting, but true).

They prefer the frozen mysis the seahorses eat, and are quick to clean the bowls when the fish finish eating–and sometimes, even before they finish…

16B15 Magellan and crab

Fortunately, the seahorses don’t object (too much) to crabs invading the food bowl. If anything, they seem to eat faster when they see the pincered bandits approaching. The crabs help keep the aquarium clean by eating the extra food before it can rot and foul the water, so I tend to leave them alone unless an unusually large number reach the bowl before the seahorses finish eating.

But if you look carefully at the photos of my seahorses by the feeding bowls, you’ll often see a crab or two in the frame.

16B15 seahorses with hermit

I have to choose crabs carefully, because not all species are reef safe, and some (like the attractive but nippy Sally Lightfood Crab) are too aggressive to keep with seahorses. Still other species feed on corals–and clearly, they’re persona non grata, at least where my reef is concerned.

The porcelain crabs are among my favorites, both because they stand out on the reef and because they’re entertaining to watch. They have a pair of “fans” on their front legs, which they use to strain plankton and other small particles from the water:

16B15 porcelain feeding

In the wild, they’re supposedly filter feeders, though all of mine will happily eat frozen shrimp in addition to filtering their share of plankton and oyster feast (the liquid foods I add to the tank for the corals)

16B15 Porcelain crab

Now that you know their photobombing secrets, keep an eye on underwater photos–mine and those you see elsewhere–and see how often you spot a clawed photobombed sneaking into the frame.

16B15 Lazarus and Weeble

What do you think about crabs? Do you love them like I do, or do you find them creepy?