Can you have too many crabs?

[Jon Fishman]

I have 4? Emeralds and a porcelain crab now.... I want a mixed reef I believe (Is a mixed reef soft, hard coral etc? I have some of everything and want more) with an anemone and just a few fish.

I am planning on stocking up my tank with more emeralds (maybe a dozen more?) along with a decorator crab or two. 75g 4’ tank now but moving to an 8’ tank.

Is there a downside to having “too many” crabs? I have plenty of live rock, and I could always toss in the occasional frozen shrimp if food source is the issue, but aside from that, will a “crab heavy” tank have any negative affect on a reef? Is 20 crabs even considered “crab heavy” or will I be fine?


I love watching these guys work their way around the scape..... They are all small now, maybe I am underestimating how big they get? I am absolutely adding at least 1 decorator, but can I safely add more crabs?

 

[AngryMike2016]

Emeralds seem to be a 50/50 shot on being safe to corals. When I had mine, he was fine, but I've read plenty of posts where people have caught their emeralds eating their coral.

 

[LynzieS]

I second the above. Especially if they aren't getting enough food, they can try a coral and decide they like it and keep doing it, then no matter how much you feed them they can still snack on corals. And I've seen a larger one take a grab at a firefish.

 

[McFly]

Crab tank sounds awesome, but risky. You would probably have to feed often to keep them off your corals or sleeping fish.

 

[LilElroyJetson]

Yes you can. They’re great for scavenging unconsumed food but there’s always a chance certain genus nip at coral. If that’s not happening, you’ll know if you have too many if you start finding empty shells (one indication that they’re not getting enough to eat if it’s not due to a predator). Just start slow and if you notice your clean up crew isn’t keeping up with the needs of your tank, add a few more (and diversify) until things are in check. Not really any hard rule for CUC because it depends on your tank maturity and needs.

 

[PatW]

Crabs are opportunistic. If they get low on food, they will eat SOMETHING. Too many crabs and they will eat fish, corals, snails or each other.

Too many snails, and the snails will just starve for lack of algae.

 

[Jon Fishman]

Maybe I will make some room in the sump for my crab wonderland. Thanks guys!