@ Biddles95 - Is this tank cycled? Or did you just go to the pet shop and get some fish? If it hasn't had any cycling done on it then I suggest you read the links in my sig... cycling a tank is basically the process of getting the filter ready to turn the ammonia fish create (which is highly toxic) into a substance called nitrites (also toxic) and then into nitrates (which aren't toxic until at very high levels).
A fully cycled filter can change the ammonia all the fish in the tank create straight into nitrates instantly.
If your tank isn't cycled and you put fish in then for a few weeks the ammonia will really build up and will often cause fish deaths. You can cycle a tank with fish as the ammonia source, or with pure household ammonia (the type you clean with...). Like I said, please read the links in my signature so you can decide which cycle you want to do. In short fishin cycling is harder for you as a keeper as it needs ALOT of water changes but it does mean you can get fish straight away, fishless requires only one water change, it often takes 6-8weeks before you can get fish but it does mean they are never exposed to toxins and when you do buy fish you can get a full tank full instead of just one or two.
So back to stocking, as a new keeper one big bit of advice is PATIENCE! lol. Please don't rush into buying more fish, plan your tank with help and advice from members on here. They'll be able to help you get the type of tank you like (active, peacful, colourful, stunning) and they'll do it without compromising the fishes natural behaviours and health as we've experienced ALOT of different fish between us all.
I suggest you take the paradise fish back for store credit and then come back and decide what cyle you want to do. Then ask for a bit of help getting your stocking idea together. Also we'll try and find you some more fish shops in your area if the one you're currently going to doesn't have a great variety of fish.
Also you will need a liquid based water testing kit and we could do with knowing the dimensions of the tank.