I have had reedfish before.
It posed no threat whatsoever to my fish, although i did loose it for around a month, I did server water changes checked my gravel and even the filter system then one day it woke me up by jumping out of the tank! (they can jump quite high and powerful, so make sure you keep something heavy on top of your tank otherwise you will wake up to a dead ropefish on your carpet (not nice)
If i remember correctly I kept him/her with smallish fish but i dont reccomend tetras as the ropefish will most likely have a field day!