Thanks for your help. I will be on the look out for a larger tank I will have a job with constant income at the end of May and will be able to afford a 100+ tank. The fish are doing great and I believe that they have grown in the week that I've had them. They look really good and are very energetic. What type of filtration sysem am I looking at getting for the larger tank?
Thanks
Graham

If you want to buy your filter straight off the shelf, I would recommend you go for an external canister filter. In my opinion, these are by far the best filtration for Oscars. There are loads on the market, I have given you a link to Eheim, one of the most popular makers of filtration. This is just one example, there are loads out there so do some research

http://www.eheim.de/eheim/inhalte/index.jsp?key=liniendetail_27523_ehen