As WD says, it will make your life easier to find out your water perameters then choose your fish to suit them; you certainly won't be short of choice. If you start buying bottles of stuff to alter your water conditions, what happens if (for any reason) you run out of it, or the shop does?. Keep it simple and you should find that you won't need to be buying bottles of this or that. Unless, of course, you are planning on keeping fish that need VERY specific water conditions.
Thanks all, I found a filter insert that softens the water in the tank as if it had been run through a home softener first.