I bet a good 50% do. I would if i could afford it or justify it but alas i cant
i not long start use it and find it help as my tap water his hard and i have use aquasate to put in tap water cost being £13.95 and r o water costing £2.00 see one i will use now and it keep hardest down more to i try to keep ph to 7.5 and gh to lows sometime his 8 when it gos greenI bet a good 50% do. I would if i could afford it or justify it but alas i cant
actually in freshwater setups few of us use ro . in 99% of instances its just not actually needed . i also kept my discus in good old tap water with no issues at all . ro is most commonly used in marine tanks where people have delicate corals/inverts etc . but for most freshwater uses its not really neccasary