Emerald (Mithrax) Crabs with 'Horses

[roguemonk]

Can anyone give me fuller descriptions of the behavior of emerald crabs (especially as they get larger) with seahorses?

I am thinking about an Emerald Crab to control macroalgae in my (future) seahorse tank. Seahorse.org does say they are usually fine with seahorses, but I have seen stories of them eating other inverts and attacking small fish. There is abundant growth of macroalgae and I will supplement with nori if he finishes it off in a few months.

Any experiences/pieces of advice are welcome. Thanks!

Brad

[smmscott]

They could easily grab a tail, and then your horse would be wide open to infection. I wouldn't risk it. You might want to investigate other ways to control that algae. I had one nip at fish and decimate my hermits, so in the fuge he went, and he battled the algae for me from in there. That seemed to work out ok, I definatly noticed when he passed away, but I dind't have to worry about any of my critters in the main tank.

[Susied]

There are many seahorse keepers who avoid all crabs but personally I have not had any problems. If a mithrax gets overwhelmingly large I give him away. There is often a lot of waste in seahorse tanks given the low flow and amount of food so crabs should have as much as they need to eat. Some seahorses are smaller than others and that should be taken into consideration. Have you thought about what kind you would keep?

[roguemonk]

I plan to keep the larger species like Reidi or Kuda.

Brad

[pledosophy]

IME they did not work out.

[Susied]

There are horror stories about crabs injuring a seahorse, I have never had that experience. However I do use tall tanks for my seahorses and the crabs hang at the bottom as long as they have food there....also my tanks are packed with live rock, friendly corals and macros so it gives them plenty of places to avoid each other.
I have not kept a crab in with capensis which are only 2-3in max but they are subtropical anyway so I didn't have to worry about hair algae much.

[roguemonk]

I have a tall tank (31") and there should be plenty of real estate. I'm still thinking...

Brad