LAUGHING? MOI
?? lol
Ok a R.O unit will sort things out but they are expensive....
about £200 for a half way decent one and if your on a water meter you'll soon notice your bill increasing
I am soon to get one of these for myself as i am setting up a Discus tank
and as anyone who knows about Discus will tell you, you need an R.O unit if your gonna keep these fish lol
I personally use a Fluidized Bed Filter on one of my tanks and they are the best thing since sliced gravy m8 lol
They are a cheaper option at around £100 for a good one and should make the problem you have a thing of the past as there is no better filter for stripping ammonia, nitrate and nitrites out of the tank water even to the point that i think you could do a water change using your water and in about 1 hour it would of stripped all the toxins from the whole tank
This is the way that i would go about it but someone out there may know a different way?
I have even used water from the tank this runs on in emergencies to set up new tanks so as to be sure that they are toxin free and when you bare in mind that the big tank its on houses my Red Tail Cat you can see its worth its salt as these fish kick out massive amounts of ammonia etc
These things really are a great invention