Could a crab eat my fish?

mpyers

New member
I have a 55gal. With two clownfish, a yellow tang, a yellow watchman goby, a peppermint shrimp, a purple clawed daumi lobster, an assortment of very small crabs and snails, and one larger suspect crab; a white spotted hermit.

The clownfish is easily 2inches long, and the goby was probably 2 1/2".

One of the clownfish and the goby are gone!
I looked everywhere, I flipped all the rocks. Tore apart all the filters, checked in the skimmer, looked all over the floor to see if they jumped. They are nowhere to be found. I can find no evidence of them or a body. They vanished.

My only conclusion was that they were eaten. But they would have had to been completely eaten in 24 hours. I would have noticed yesterday if they were gone. (Possibly not the goby.) But certainly the clownfish. I only have 3 fish that swim around! I knew that eventually the crab would get too big (they grow up to 10 inches.) and that I would have to move him to the sump or get rid of him. My plan was to put him in a sump when I got one. (I literally bought a drilled 65 gallon with a 35 gallon sump TODAY to replace my sumpless un-drilled 55gal). He was going in the sump tomorrow.

He can't be any bigger than an inch and a half. I've seen him out of his shell when he got the shell stuck in between two rocks and crawled out to get it un-stuck. I can't imagine that he would be able to consume a clownfish and a goby in a day. Even with help from the other crabs, shrimp, and lobster. I can't imagine that all of the biomass in the tank could dispose of two bodies that size that quickly at all. There has been nori on a clip non-stop. I have been overfeeding lately because the yellow tang is very skinny, and not eating well. There is also a zuchini that has been bobbing around the bottom of the tank that I've seen every animal pick at. So its not like they're starving.

I can't even imagine that anything in there could catch them?

I don't think that even if they just died of disease then got stuck to a powerhead or the skimmer pump that they could have been tore apart quick enough to be decomposed. There would surely be a corpse right?

Please lend me some insight. What happened? How do I prevent it from happening again?
 
Crabs are trouble in a reef tank. They cannot be trusted. I had one kill a clam. They'll kill a sleeping fish. Lobsters, too. Do you have a screen for jumping?
 
Are there any strictly herbivorous crabs? Should I quit buying them, and just stick to snails? Do I need small crabs as a clean up crew?
 
The only crabs I have in my tank are a couple of emerald's for bubble algae control (largely ineffective, btw) and a few tiny scarlet reef hermits. IME, the scarlet reef hermits are the only ones that won't eventually bother something they aren't supposed to.
 
You'd be surprised how quickly a fish that dies gets 'broken down' to the point that there's nothing left to find. While it's certainly possible the inverts killed your fish, it's more likely they died and then got scavenged.
 
The lobster? Really?! I suppose I won't be too upset if I need to get rid of him. He never comes out from his hiding place anyway. Everything I read about him said they were non-agressive. I'll put him in the sump with the big crab.

The lobster is an inch maybe inch and a half long.

None of the other crabs are bigger than a quarter.

I'll get pictures tomorrow. I just moved everything to the new tank so it's too cloudy right now for pictures.
 
The lobster? Really?! I suppose I won't be too upset if I need to get rid of him. He never comes out from his hiding place anyway. Everything I read about him said they were non-agressive. I'll put him in the sump with the big crab.

The lobster is an inch maybe inch and a half long.

None of the other crabs are bigger than a quarter.

I'll get pictures tomorrow. I just moved everything to the new tank so it's too cloudy right now for pictures.

Those lobsters are known fish eaters.

But as said before it's also highly possible they died of illness and were scavenged.
 
How would I know if they have an illness? There haven't been any spots, or odd behavior leading up to it missing. One fish has developed an eating problem. The others seemed to eat and swim happily. Also, I haven't introduced anything recently. No spikes in any parameters.
 
This one is big-ish. But barely even moves. I couldn't imagine he did anything wrong. I've had him since the first day I got the fish as well.

 
I also have some dwarf red tips. I didn't get a picture, though.

I think from the horrors I've been reading that I'm going to get rid of the lobster and the monster crab. And let the rest die out. I'll just stop buying them.

Snails all the way.

What is a good replacement for crabs as a clean up crew besides snails? (Personally, I think snails are worthless as well.)
 
I also have some dwarf red tips. I didn't get a picture, though.

I think from the horrors I've been reading that I'm going to get rid of the lobster and the monster crab. And let the rest die out. I'll just stop buying them.

Snails all the way.

What is a good replacement for crabs as a clean up crew besides snails? (Personally, I think snails are worthless as well.)


Personally, and this is simply my opinion.

Don't buy animals for their "jobs". CUC are pretty useless if you ask me, and although some do a good job at breaking down animal waste, they still produce waste themselves. Nothing is going to replace good husbandry. A reefer with a siphon, an algae scraper, a tooth brush and a turkey baster is going to accomplish more in five minutes than a CUC can accomplish in a week.
 
When I bought him he was tiny. Grew like a freaking weed. The lady at the lfs said he was reef safe (she has a marine biology degree and I still can't trust her). Then after he grew out of shells to live in, I researched how big he was going to get. That's when I found out he was carnivorous. I planned (and have now) to put him in a sump when I got one, and like I said in the OP I was literally less than 24 hours too late. I set up my new tank yesterday and put him right in the sump. I'll likely find somewhere to take him Because he can't stay in what is going to be my fuge/copepod breed ground or he will eat all my copes.
 
I'm on that team now. Right from the start I thought the crabs were cool, and the lfs told me that I needed a CUC of at least one crab or snail per gallon. I figured they were trying to sell me more animals, but I didn't realize that they were worthless. There has always been **** floating around bottom that they don't eat. They just crawl all over my corals and knock **** over. They don't scavenge anything.

Plus the empty shells from the dead ones are ugly laying all over my tank looking messy, and I left them there for growing crabs, but I'm taking them out as they die now.
 
I don't know... I've found my CUC fairly essential, but for crabs, I only use red scarlet reef crabs and blue leggeds, which I've observed to be mainly herbivores or scavengers. As far as I've seen, they won't murder fish. But I also have turbo, Astrea, coralline margarita, and nassarius snails also helping out. I even chicken out with emerald crabs. Crabs are a funny bunch, I once had a freshwater tank with dwarf mud crabs (claimed to be solely herbivores), yet I saw one snap a very healthy, 4-week old juvenile fish in half. I was very angry. I loved that fish. You just never know. I think you really can judge it more by the size of the claw. Get the crabs with the itty bitty pinchers.
 
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