Pah mineral oil is for wimps.
Using something like MCT 40, or Feser One would cool better over mineral oil. Or better yet, Use something like Liquid Nitrogen cooling would work exponentially better than any water-cooling setup. Even a generic refrigeration unit would work better than a water-cooling setup
While fish tank cooling is quite awesome, It's definitely not the world's best PC cooling system, it's only mildly better than a standard water cooling set up if done properly.
If you have a exorbitant amount of money to waste, there is a PC manufacturer that specializes in Fish tank computers, and they also happen to look considerably more elegant than a computer put into a fish-tank.