Oh! so wonderfull... I watched the tank and it turned all murky for two day, & then it turned as crystal clear as ..... well..... Crystal.... Tonight I braved another (scew) guppy fry in there and he was happy (as a fish in water)... I have now removed him and put a prize specimenn in the tank with 3 females... I've never seen my Guppies happier... Aircon (dripoff) water can work!