Mexican orange dwarf crayfish attacking other fish

[Martin]

I recently bought two Mexican orange dwarf crayfish from Big Al's, I bought them because I kept on reading that they're docile and won't attack fish. I put them in a 20 gallon that also has otos, albino cories, amano shrimp, and a Betta fish. Within an hour one of the crayfish jumped up to grab one of my otos stuck to the glass. The oto was out of the crayfish's way and not doing anything. It held onto the oto for around 10 or 15 seconds, then the oto escaped. Today I also saw my Betta swimming frantically with a crayfish grabbing onto his fins. I couldn't get the crayfish off by poking at it and didn't want to catch them and pull the crayfish off by force. This went on for around a minute until the crayfish finally let go. Is this normal behavior for Mexican orange dwarf crayfish? They have been eating shrimp pellets. Is it possible that the ones I got are a different species than the peaceful kind? I have a 20 gallon shrimp tank (where I also breed shrimp), would the crayfish do better in there or would they eat the shrimp? The shrimp are small blue dream shrimp, with a lot of babies. There's no fish in that tank.

[lucius]

I had the same experience with self cloning crayfish.  I was told and read that they won't go after fish so I put two with my black moor goldfish.  A couple days later I see my black moor swimming funny and discovered that one of the crayfish had latched onto its tail and wouldn't let go.  The black moor was three/four times the size of the crayfish.  I then separated them into two other tanks I had.  A few night later and I see one of my bolivian rams upside down.  I turned on the lights and one of the crayfish had gotten a hold of it and was eating it. 

So no more crayfish for me.

[flyingpancake]

They eat shrimp as well

[Martin]

They're cute and fun to watch but evil little things. I moved the fish around and moved my Betta to another tank but he's pretty beaten up. So far the cories seem fine but the crayfish do seem interested in attacking them. The cories swim away whenever one of the crayfish gets close. The crayfish are eating so I don't think they're attacking due to hunger. I read so many websites talking about how peaceful these crayfish were. I'm going to try to sex them soon, maybe one gender is more aggressive than the other and I got the aggressive kind.