Poll: are emerald crabs fish safe?

[Forsaken77]

I've had green emerald crabs and they would grab a sleeping fish and kill it.

I think it depends on how hungry they are, but fish that are in reach are fair game to them. I even witnessed the big one grab a fish by the tail so it couldn't get away.

If there's enough food for them, they'll probably leave the fish alone. But everyone has seen the videos of a fish swimming by the crab and it raises its claws at the fish.

I haven't kept them since.

 

[vetteguy53081]

No problems with them and co-inhabitants however I have seen them bugging my coral

 

[mike werner]

I agree with others, I don't believe stories about them killing fish. I think most of the time that fish got sick and died without the owner knowing and the crab took advantage of a nice meal. That said, corals can be fair game with them if they're hungry.

it would have to be on steroids or smoking spice to catch,kill and eat a fish.a coral banded shrimp has a better chance.i call bs on anyone who says they have witnessed this.

 

[shred5]

Never a fish but he ate my shrimp and about half a dozen before I figured out what was happening to them. I have had them rip corals apart. Ate the flesh right off a sps.

 

[shred5]

it would have to be on steroids or smoking spice to catch,kill and eat a fish.a coral banded shrimp has a better chance.i call bs on anyone who says they have witnessed this.

Why not .. I have never had one do it that I know of but why could it not happen at night? Serpant stars catch fish on occasion!

 

[mike werner]

Why not .. I have never had one do it that I know of but why could it not happen at night? Serpant stars catch fish on occasion!

ya know the saying. I believe half of what I see and nothing of what I hear.i'll believe half when I see a video.
that crabs just slow man. a turtle gotta better chance of catchin a squirl.lol

 

[mike newell]

My tank is fairly small (Red Sea Reefer Nano). 21 gallon display with 6 gallon sump. I have some algae in the DT that is a bit too big for the standard CUC crab. The algae problem isn't that bad as my entire sump is a big refugium powered by a Kessil H380, but still there are some patches and they're growing slowly so I want to get ahead of it. I don't want to feed less (I feed the fish once per day and the corals twice per week) as my SPS coloring loves having some nitrates in the water.
I've been thinking about getting an emerald crab to go after this algae, but my research on how safe they are has been very inconclusive, which is why I want to do the poll. I have two clowns, 1 helfrichi firefish, and 1 Biota captive-bred Mandarin from AlgaeBarn (don't worry he eats prepared foods and is the fattest fish in the tank ). Having said that, these are all small fish. I'm not too worried about the clowns, but the firefish and mandarin sleep in the rock work and I don't want them to fall victim to the emerald. Thoughts?

I have a 12 gal. tank that occasionally has had algae problems. The tank has been up for 10+ years. I have used emerald crabs without problem until the currant one. He refuses algae, doesn't mess with other occupants, just comes out and takes whatever I am trying to feed. He (it) is the largest one by far, that I have ever seen. Good luck!

 

[Young@Heart]

Have had several in my 55 and now my 180 they have never been an issue. I am a relative newbie and I consider myself very cautious.

 

[Lionsreef]

I've had problems with one of them nipping at my clam mantle.

 

[BigJohnny]

One of mine ate acro polyps for a short time when first introduced and then got in a fight with my midas blenny (not sure who started it) and cut a nice gash on its head. It recovered nicely though. My guess is it came too close to the midas hole and midas tried to knock it away. Ive seen my midas pick up snails/hermits and throw them against the glass so im guessing he started it lol. Been fine ever since.

I have 2 in a 90g and they don't bother anything anymore (maybe kill a hermit now and then but hard to tell). I got them to eat bubble algae but they don't touch it or much else unfortunately.

 

[HereWeGoAgain]

My two emeralds haven't bothered my 2 clownfish, a blue tang, or a long nosed hawkfish.

 

[KMKoolreefs]

I have six in a 90 gallon but I’ve been having problems with one fully grown emerald crab. It used to be very defensive toward my larger fish and a six line wrasse almost trying to grab them if they got close. Now it occasionally rips pieces off some leather frags and has recently damaged my elegance coral after feeding it. I’m considering removing the crab now. I vote emerald crabs are only reefsafe and great algae eaters when small, and reefsafe/fishsafe with caution as adults

 

[Crimsonphoenix]

I have had 3 different 1 1/2 - 2 inch emerald crabs in my 36 bow at different times. They were excellent at eating all of my bubble algae and never bothered my clowns or anthias. BUT after the bubble was eaten it would hang out and pick at my lobos. I put him in the sump for safe keeping!

 

[vetteguy53081]

I hear from many of them annoying or destroying coral at some point of occupancy in tanks.

 

[ArowanaLover1902]

It all depends on the individual I guess, but I'd say most young emerald crabs are reef safe, the bigger the get, the more confident and more omnivorous they are.

 

[navathehutt]

I'm going to drop some in my fuge, didn't want them to go after a nudi,or urchin but theres tons of food in there. I think i got them confused with sally light foot which are little demon spiders , my dog ate it though when it jumped out of tank so karma.. haha

 

[jd371]

I had a total of 4 in my 75g but one of the small ones was eaten and out of the three left over I only see one on a regular basis. I got them to help with GHA and have seen them eating it but not as much as I hoped. I see one on my Duncan from time to time and thought it was eating it but after spending some time watching it he's not eating the polyps but picking stuff off around the head of the Duncan and in between the stalks. I don't see any damage to the Duncan.

 

[jeffchapok]

I haven't had any harm to my fish from emeralds, but they are hell on hermit crabs.

 

[LIreefguy]

I have had emerald crabs In my reef tank for over 10 years now. I never seen them do any damage to any fish or any corals. Except maybe knock a newly glued frag off. I also find that this and any other algae control species does better at keeping algae under control then eliminating it. If you expect to drop 4 little crabs in a 75 gallon tank and have wipe out a hair algae outbreak. That probably won’t happen unless you get the underlying problem under control.

It’s also why I prefer trochus snails

They will breed in your aquarium. So if you add 10 they will multiple under they reach the correct level to keep up there needs

People always try to tell you how big your clear up crew should be but my tank is different than your tank. This way nature kinds of control it

I started with 10 in my 265 and 5 years later I have like hundreds big and little ones. I actually give them away when people buy corals from me

It’s amazing to see when they breed. Those little snails will cloud my whole system for hours and I have 600 gallons of water

 

[Dondante]

Mine was scraping a bird's nest. He had to go in the sump.