Emerald crab ate our firefish!

[acronce]

We had a nasty nuisance algae problem so I got a couple of emerald crabs with a clean up crew. One is pretty tiny and we rarely see it during the day. The other is bigger, with the carapace maybe an inch across. It's molted once and is a nice green color.

 

Most of the bubble algae is gone, but there's other macro algae to eat. We've been trying to not overfeed, so there's little waste. We often feed with pellets, some of which ends up on the bottom. I've seen the crab eat pellets, but I haven't tried to specifically feed him.

 

This morning my wife found the big emerald eating our purple firefish, and fighting off the peppermint shrimp (we have three of those). I think the firefish was healthy. He was a really good eater. We had the firefish for over a year.

 

I believe our water parameters are good, although we've had a heat wave this week and we don't have a chiller. Temps have peaked around 85 degrees. I have a Neptune Apex that emails me when temps are above 84.

 

At night the firefish would hide in crevasses in the live rock. Is it fair to assume that the emerald just caught the firefish napping and killed it? I've only got circumstantial evidence, but it does seem like the emerald is guilty.

 

If that's the case, then I probably have to catch the big emerald and banish it to the fuge. I think I'll leave the little emerald in the main display for now. Maybe with the big one banished, the little one can move around more freely.

 

This is really a shame. You try to solve one problem, and it creates a new one.

 

I'm worried that our tiny rainford goby will be next in the menu...

 

Any suggestions or thoughts would be appreciated.

 

Best,

--

Allen Cronce

Edited July 8, 2011 by acronce

[Bongo Shrimp]

It's highly unlikely that the crab actually caught and killed the fish. The firefish was most likely very weak or even dead before the crab got it. The crab was then just doing his job- cleaning up.

[7digits]

+1

[mndfreeze]

it is possible the crab could catch it at night when it sleeps in the rocks, but still very unlikely.

 

I vote firefish dying of something, most likely 85 degree tank temps unless I read that wrong.

[hooligan_78]

I have had many mithrax crabs over the years; IME they are pretty much the most docile things in my aquarium. I have never witnessed one catch and kill a fish, they aren't even that fast. A sallylightfoot, for sure; an emerald crab highly unlikely. I vote with the rest...firefish had problems.

Edited July 20, 2011 by hooligan_78

[bensanders]

Firefish are easily one of the fastest/most agile fish we put in our tanks. Highly unlikely that an emerald crab would catch and eat him, unless the fish was already sick.

[hooligan_78]

Pretty much, every firefish I've had die was death by carpet...not by crab.

[Bill Nye]

I disagree that the emerald could not have killed it. Ive seen large emerald crabs grabbing at fish during the day, I would imagine at night things could get pretty serious.

[ry05coupe]

I disagree that the emerald could not have killed it. Ive seen large emerald crabs grabbing at fish during the day, I would imagine at night things could get pretty serious.

 

+1. My firefish also has a little hole that's about 1/4" in diameter and maybe 3-4" deep into some live rock that it sleeps in at night. I could definitely imagine an emeraly crab blocking off that opening then just going at the fish.

[burtbollinger]

i have personally witnessed an emerald crab kill both a pair four line wrasses and a purple firefish. the fish were perfectly healthy at the time. as usual, folks on boards giving advice without real-life experience to back it up on NR...

 

Bottom line...Emeralds kill by grabbing and not letting go...I've seen it happen....not just read about it. They are NOT reef safe.

Edited July 20, 2011 by burtbollinger

[bensanders]

as usual, folks on boards giving advice without real-life experience to back it up on NR...

 

I own a purple firefish and an emerald crab, never had an issue with them or any fish and a crab. Not saying it doesn't happen or couldn't happen in the future, but I've never witnessed it. That doesn't give me any less "experience" than you, it just means its never happened in my situation. I gave my opinion, along with others, that it's unlikely for an emerald crab to catch and eat a speedy firefish. If it happened to you (or others), then it gives you the same amount of experience on the matter, just with a different perspective.

[burtbollinger]

fair enough...

[mndfreeze]

Burtbollinger, if you witnessed such an event then I would say bravo to you sir, for seeing the rarity it is. That is about the equivilant of you chucking a home made spear at a cheetah running full speed away from you and zig zagging inside and out of small chunks of rocks and trees and nailing a killing blow. Oh, and with massive muscle cramps in your arms.

 

mithrax are SLOW SLOW SLOW. They raise claws and 'snap' more in defense then in agression to eat but if they got super super lucky of course rthey are going to eat the damn thing. There are plenty of types of crabs that look very similar to emeralds and are often mistaken as them and I can easily see someone having one, being sold one, being CONVINCED because someone on a forum say 'matter o fact' it was, then having it kill a fish.

[Bill Nye]

Burtbollinger, if you witnessed such an event then I would say bravo to you sir, for seeing the rarity it is. That is about the equivilant of you chucking a home made spear at a cheetah running full speed away from you and zig zagging inside and out of small chunks of rocks and trees and nailing a killing blow. Oh, and with massive muscle cramps in your arms.

 

mithrax are SLOW SLOW SLOW. They raise claws and 'snap' more in defense then in agression to eat but if they got super super lucky of course rthey are going to eat the damn thing. There are plenty of types of crabs that look very similar to emeralds and are often mistaken as them and I can easily see someone having one, being sold one, being CONVINCED because someone on a forum say 'matter o fact' it was, then having it kill a fish.

 

I dont know how reef safe emeralds are, regardless of eating fish. The one I used to have was a smaller guy and he would pick at coral and beat snails and hermits all day. IMO emeralds may be slow but they have the strength and desire to eat fish. You dont have to be very fast to eat a sleeping fish.

[bioload]

I won't have another emerald crab in my reef tanks.I have personally witnessed them too many times climbing all over my sps corals and even worse plucking and eating polyps, NOT algae between the polyps. Very small specimens seem safe for a while but they become huge, menacing and destructive IME.

 

EDIT: I have not personally seen them catch and eat a fish but the above is plenty enough for me to stay clear of them.

Edited July 28, 2011 by bioload

[Jillianberra]

On 7/20/2011 at 2:58 PM, burtbollinger said:

i have personally witnessed an emerald crab kill both a pair four line wrasses and a purple firefish. the fish were perfectly healthy at the time. as usual, folks on boards giving advice without real-life experience to back it up on NR...

 

Bottom line...Emeralds kill by grabbing and not letting go...I've seen it happen....not just read about it. They are NOT reef safe.

I second. I have recently witnessed one of my emerald crabs waiting on the rock crevasse that my fire fish liked to swim in. He waits with his claws up and tries to grab him. The next day the fire fish was dead. He has also eaten a 6 line wrasse. And taken a huge chunk out of my diamond gobys tail and I haven’t seen him since.. rip. 
 I have a 32 bio cube and have read NUMEROUS posts about this, each however just talk about how there’s no way it could be the emeralds theyre reef save and must be starving and oh all your fish are weak and sick, WRONG. I’ve seen it and if there are chunks out of fish and they disappear the next day, i have no idea what else in there could be responsible for that.  
 

I would like to know if there is any other snail or less aggressive mini crab I could put in tank for algae growth. I have a Lawnmower blenny and he is awesome but I just want something that will help him out without murdering other fish. 

[johnmaloney]

Firefish live around 3 years, if you got him as an adult, and had him for a year....may have just been his time.