Hello Mate
I keep a small aquarium of 6 fancy goldfish, got them mainly cos their stones went well with the kitchen decor (dont ask me, was the misses idea), the tank came as a kit, with pump, stones & obligitry sunken pirate ship, with the 6 fish & a bit of plant I think it came in at less than £40-50.
And to be honest with you, it's realy relaxing to watch. Feed them 3 times a day, only need cleaning out about once a month & in the summer they even breed... Although they eat the eggs before any hatch.
Cheers.
Stuart