Blue Knuckle Hermit Crabs

[childress5tyler]

I found a LARGE blue knuckle hermit crab in my tank today and did a little research on them and found that they're semi-aggressive. For those who bought these and have them, are they aggressive in your tank and if so, towards what? Have you had luck with them? Thanks


Keep calm and reef on

 

[kchristensen8064]

I've got one and within being in my tank for 2 or 3 days, the only inhabitant that it's bothered was a large snail that it decided had a really nice shell so it took it. Other than that it's been a model citizen towards all my fish, snails, crabs, and corals. I don't mind the snail murder the shell looks a lot better on the blue knuckle than the one it came with.

 

[mcarroll]

All hermit crabs are omnivores, and all take shells for housing.

Of course this means your snails are always potentially on the menu....it helps a lot if the snails are significantly smaller or larger than the hermits. Also have some empty shells around the tank that are just somewhat larger than the hermit's current one. Know that they choose shells based on vanity as much as anything though, so don't be surprised if they take a shell that's a little smaller just because it looks better.

In fact, expect them to eat anything they want (they can eat anything they can catch), with a slight preference for algae and dead stuff. (I think this is just cuz they are easiest to catch.) Smaller ones tend to be able to satiate themselves on algae and the associated microfauna...bigger ones will exhaust their supply and start hunting for "alternative food". Could be leftovers from fish feeding...hope it is. FWIW, depending on the tank I keep about 1 hermit per 25-50 gallons these days...or none.

Unless (until?) you find damage that yours has done, I don't think I'd do anything but let him be at this point. And all that said, they are really cool looking and interesting to watch (as are all hermits). Could be worth a tank of his own if he can't get along in the reef! (Takes very little to maintain a hermit tank.)

-Matt

 

[ECOAQUASCAPES]

I found the Blue Knuckle Hermit Crab, "Calcinus elegans" the most perfect crab to have in a full blown reef system. They require an assortment of shell sizes until full grown. Their blue coloured sections never fade and look vivid. They do not require direct feeding. They stay smaller than a golf ball and I found them to be both diurnal and nocturnal. They may hide now and then, but are a sight to see when they show for a few days, all this irregularly. Since 1995, I have never seen any specimens do any harm to any other type of other saltwater creatures. Weird, truly reef safe?