Shrimp killer?

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hubkri42

Aquarium Advice Newbie
Joined
Jan 20, 2021
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Small 10 gallon desktop aquarium with cherry shrimp, 1 remaining pygmy cory, 3 pygmy hatchets, and 5 chili rasboras all cohabitating nicely for the past 6 months. Occasional predation of shrimp babies, presumably by hatchets but steady shrimp population is slowly growing. Yesterday added*rabbit snail, 5 additional pygmy cories, and 6 green rasboras and have had 2 decapitated moderate sized shrimp in the last 12 hours. The remainder of the bodies were intact. I haven't seen the rasboras leave the main water column and shrimp have been free swimming past without any signs of the fish nipping at them. One of the cories was feeding on the decapitated shrimp after I first noticed it (not the initial kill) and the most recent body was tucked in a back corner behind rocks where it seems like the rasboras wouldn't go, but where there was recently a snail and a cory. Best bet on the killer to remove to another tank? Seems like it would be the rasboras, but location of the bodies at the crime scene doesn't really match...
 
Well, I have seen my teeny tiny Pygmy Cory biting my Betta's tail while the Betta was at the top of the tank resting in a bed of moss. I don't think it did much damage, and it lived for ages with 30++ Ghost shrimp and they all lived together.

Are they Neon Green Kubotai / Microdevario kubotai (Microrasbora kubotai)? These guys are very busy active fish and although they mainly are at the top, I would be suspicious.

Not 100% here for which new fish. But that when there are new additions, there is a reduction of free space and a new volley for areas /territory, and the peacefulness which might have been enjoyed before when the dynamic changes, and these new fish, were not raised together with the other new fish.

Rabbit snail should be innocent!

As for where the shrimp bodies end up it would seem the flow / current of the tank will make a body go to corners. With the heads nipped off, sound like a quick bite off, of it and still stay up top, not going after the whole shrimp?????
 
Yes, sorry should have specified, M. kobutai, although I'm surprised at their size. They are easily twice as big as the chili rasboras I've had for a year now. No obvious deaths overnight, so hopefully the carnage has ceased! I'm fine with the fish picking off shrimplets on occasion but try to avoid tank genocide. :nono:

Thanks for the insights!
 
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