when I kept marines and discus as a student, I bought one of these and made the water up to correct salinity/pH etc as required – well worth the investement.
Had it set up under the kitchen sink using a self tapping tap and ran it into a lab grade plastic drum (so minimal nasty plastic chemicals) – my housemates hated me, but as I had been there longest they got told to shove it…had 5 tanks around the house in the end 2 marine and 3 discus…and obviously no girlfriend at the time!
bought it from wetpets – great service, but I expect there are cheaper (cant remember the model as it was over 10years ago now and sold it on)
would also recommend getting decent UV steraliser and a trickle filter (or even going the whole hog and having a plenum tank with some living rock in it for filtration (which is what I always wanted to do)
