Anableps and the sp. 'xingu I' won't really cohabit with each other peacefully for very long. Once the pike starts gettin size and aggression it will REALLY lay the stomp on them. However, how brackish do the anabs have to be? I normally add about 1.5 tablespoons for every five gallons of my aquarium water. Its not brackish, but it does help the colors and vitality of the fish. Not sure if that is enough for the anabs. though. I definately would be cautious using any more than that with the pike as well, as it could prove to be fatal. HTHs