Jess, I'd steer clear of clown loaches if I were you hun - they can be quite problematic fish and need spot on tank conditions. They are extremely notorious for getting white spot disease and even with medication they usually end up dying (I'm sure if you were to do a search on these forums for Clown Loach, you'd probably find lots of posts about sick clown loaches). I think clown loaches are best left to the more experienced fishkeepers (just my opinion - I've tried and given up for now) - so maybe in a few years time you can give them a try. But, again, they do grow huge (if they are lucky enough to escape disease) and this is the problem you already have with your current 4ft tank set up with fish that are going to be too big for it.
Go for something that doesn't grow to such large proportions for your 4ft tank. In the 6ft tank - well, you have more scope - you lucky thing! Cichlids would definitely be my choice, too - not only are they beautiful but they have such great personalities and character. Lots of cichlids to choose from, too. And you have a whole year to start planning it all and doing as much research on your chosen fish as possible. Gosh, I can just imagine how excited you must be - counting down those months and weeks, eh?
Take care - Athena
(few close shaves tho)
