There is the new Maidenhead Aquatics in east bridgeford and they do good marines and trops even if they don't have as many tanks as some of there other stores. Wharf isn't amillion miles away and thats supposed to be one of the best shops in the country, personally however I am not a massive fan of the place seen better. But it depends on how far you find it acceptable to go I know to people who happily travel 100miles once twice a week to there favorite shop.
That is something I would never do, travelling in excess of 20-30 minutes to get to an aquatic store is stupid and pointless im my opinion - unless they have very rare fish in that can't be obtained in areas nearby. As for corys etc, it would be silly to travel that far.
East bridgeford would take around 40 minutes drive from Newark, and I dont think my family would justify travelling that far, its very rare for them to travel to west bridgeford garden centre, let alone elsewhere.