i have 21 inch silver arrowana in a 6'x18"x18" tank and it is not good it is sat on the bottom with it's tail and lowerbody curled up against it's body whenever i go near to the tank it suddenly shoots off to the other end of the tank does anybody know what is wrong wth it i have 2 8-10 inch oscars in with it they are acting fine any body have a clue
