Thanks for all previous advice - now have 2 tanks, plus a spare small one which I keep going as a spare for emergencies.
Got a bit of an issue with my Ruby shark at the moment - he is in a large tank with a Pleco and a Rainbow fish, has been for years (although was a smaller tank before we took them off a family mamber and gave them a tank that suited thier size).
We read the Rainbow fish should be in a group, so we got 3 more, slightly smaller/younger, to make his life a bit better - only problem is the Ruby Shark continually chases the 3 smaller fish and looks to be attacking them, which is unusual for him as he is normally quite docile.
I have moved the Ruby into the spare holding tank, what should I do next to integrate them - dont want to be running 3 tanks, or for the Ruby to be on his own??