I got an emerald crab just five days ago and i came home today to find that the little @#$!%@!*^#% shredded my green BTA. I am furiouse, not only did the little sob not take care of any bubble algae but he is a filthy murderer!!
I've got one that hugs SPS coral at night, won't let the polyps out, and likes to rip out the polyps of my chili cactus. That #@*%! thing scampers off everytime I go near him to get him out...guess I better get a trap.
I have only 3 scarlet reef hermits in my 55, no problems with them for the last few years, but the minute I think they are up to no good....they are history... :badgrin:
On the emerald....not sure on the validity of this, but I remember reading an article a few years ago that claimed that around 40% of all emerald crabs found in LFS tanks were in fact not emeralds, but a close relative that was nearly physically indentical, but much more omnivorous and problematic in a reef tank...like I said, not sure on the validity of that.....
I have a small crab (shell probably about a dime's width or a little less across) that came in on some live rock. I'm pretty sure he's molted at least twice in the last year so he's growing at a decent rate, and I know I'm probably going to have to go after him one day. Recently I've noticed that my yellow polyp colony is disappearing. Anybody know if a crab might be the culprit?
I have peppermints, and I frequently see one picking at my corals pulling polyps off. Just last night one ripped a polyp off my green frogspawn. Don't know if I will get anymore. They seem to be mostly useless... mostly cause they do take care of aptasia... but it's been all gone for a year.
I have no shrimp at all in that tank, but I do have a fire shrimp in my 30 gallon hex. Unless someone knows that the fire shrimp would bother the yellows I may just transfer them in there for now. Hopefully in a few months I will be moving the reef into a slightly larger tank and can get rid of a few problems in the process.
I've only seen the crab half a dozen or so times, but he seems to stay in one general area. Hopefully I can corner him in the move and show him the door!
All you crab sufferers might want to try the bait-in-a-glass trick. Don't feed the tank for a couple of days, then silicone or putty a piece of shrimp or fish into the bottom of a tall, narrow glass. Right before lights out, lean the glass against the rocks at a sharp angle, where you've been seeing the crab. Chances are, some type of crab will be in that trap in the morning. Crab goes in for the bait, can't get back out.
I have kept one emerald crab in both my 29g and now my 55g and I have never had a problem. I have yellow polyps in my new tank so I will keep an eye on the crab. It just likes to hang around my ball coral but never picks at it that I can tell. It is forever scavenging for food.
For the people having problems with emerald crabs, are you feeding the little guys? I add some seaweed everyday. There are two emeralds in my 25 gallon tank and one is rather large. I haven't had any problems with either of them. Just remember that a reef tank needs to have preditors to help balance the ecosystem. Some might even nibble on corals once and a while but will be benificial else where in the tank...... Just a thought....
ok seriously, crabs by nature are opportunistic feeders, many when young feed on algaes (mythrix). yes this can be benefitial to an aquarium, but remember that in the ocean there is a lot of room to move around. these young crabs will graze hereand there taking their favorite lil bits and move on. in a confined environment they cannot do this. therefore they will be forced to eat more food in one area, thus they will look harder for something they really want. if this means pulling your prize Zo' out like dandylions form your lawn just to see if there is something good hidden between them,,,they will. if they find a tasty morsel on your sinuaria, they will think there is more, so they can dig into it trying to find it, reguardless of the damage inflicted on the sinularia.
now these crabs are getting older, and bigger, their diet is changing, their bodies require more protiens, what has more protien than algae?...yup, flesh, now opportunity becomes a factor once again, if they can get the same protien from snatching up a snail and spending 10 minutes eating it as they would get from 2 hrs of grazing,,,,bye bye snail. if they find small fish sleeping (remember crabs are night active also) fish could very well be on they menu. i have even seen small holes in larger fish that came froma crabs eating on them while sleeping. (some tangs can be sound sleepers....the sea monkeys got my money)
so in my few deacdes of reefing i have come to the conclusion that crabs belong in the ocean, or on a plate, but not in a reef tank. even the most placid lil "oh he has never caused a problem" crabs, has a demon inside, the demon of opportunity and sooner or later the moment will come, and for us when it does....its too late.