Adding the clean up crew crabs!

The Cleanup Crew II: Crabs

Crabs are another invertebrate that you can add to your nano tank. General recommendations are only 1-2 per 3-5 gallons if small and only one if they are large. Some types can be semi-aggressive and some might pick at corals. Others have good advantages in that they eat leftover food or detritus. One eats a pest, bubble algae. Choose wisely.

Emerald crabs (mithrax)

This is a green crab with heavy claws and hair on it's hind legs. It is primarily nocturnal, hiding in crevices during the day. Generally not aggressive. Very hardy and eats algae.
Advantages:
they eat hair and bubble algae
very hardy

Disadvantages:
they may not control ALL the algae
some may pick at your coral, though, I haven't seen this
larger crabs might become aggressive
they will steal food when spot feeding, eg, with sun corals



Sally Light Foot (Nimble Spray crab)

This crab generally gets a 'no vote' in the nano reef community. The crab has yellow markings around it's joints and a green-brown carapace. Primarily algae eaters and very active.
Advantages:
pick at algae on LR
they eat left over food
very hardy.
Disadvantages:
this crab has been known to attack your corals
they can walk over corals and disturb them
can compete aggressively for food
larger crabs have been accused of attacking shrimp




Hermits

First off, there are some nano-reefers who don't put hermit crabs into their tanks. It appears that some may get aggressive and darn right thefty. Not only can they steal food from others, they can steal their homes. They can be very good scavengers though, so, you'll decide on whether or not to use them. My opinion on them is that they are underachievers

1) Red leg hermit--these are dark red with yellow on the eye stalk and claw tips.
Advantages:
very hardy
good scavengers
clean algae and diatoms
Disadvantages:
can grow fairly large
can uproot corals and loosen rocks



2) Left handed hermits: this hermit's left claw is larger than the right and is used to close off the shell. It has long eye stalks. Herbivorous.
Advantages:
sifts and aerates the sandbed
reef safe
can eat red slime algae (cyanobacteria)
Disadvantages:
vulnerable when molting/leaving it's shell
bold temperament




3) Blue legged hermit:This is a small hermit crab with bright blue legs. They are scavengers and will eat detritus and algae.
Advantages:
very hardy
reef safe
they stay small
Disadvantages:
they have pugnacious reputation; they have been known to harass and attack other snails
needs new shells as it grows, thus, need to keep some shells in the tank (likemost hermits)



4) Scarlet Hermit: another common hermit to add and my favorite. Pretty easy to find around the lfs.
Advantages:
common to find
reef safe
reputedly less aggressive than other hermits
hardy
stays small
Disadvantages:
not many



CAUTION:
Arrow crabs: don't go there. Quite adept at cornering fish and eating them. Too aggressive for a nano tank
Spider Decorator Crabs: may disturb your corals
Gorilla crabs: if you get one as a hitchhiker, bad crab. Try and oust it.