What sort of temp is your tank at as I read that Amano Shrimps are best suited to tempretures under 25 degrees but it doesn't say a lowest tempreture for them.
Amano shrimp, Caridina japonica The Yamato, Algae or Amano shrimp has been made popular by aquascape expert Takashi Amano. It's a small species, fully grown at around 5cm/2", which is found in Taiwan and Japan in cooler mountain streams. Therefore it does best at lower temperatures (under 25C/77F).
the only thing i can c compatible is the Atyopsis gabonensis (Cameroon Armoured Shrimp)should be big enough and armoured enough for fantails to leave alone and can go t 22 degrees c so a heater to stabilize temps at this and stop it getting eny lower would be a good idea