Bottle water is great. Here we have places to buy good RO drinking water for a quarter a gallon.

Rockwool can be tough to keep the Ph stable at first. Yes you soak it in Ph adjusted water for day's before you use it. You need to cover it too and keep the light away because it will grow algae very fast.
Zandor Reviewed by Zandor on . water problem hi, ive just recieved my gro tank 205 thru the post. the problem i got is the instructions say to soak the rockwool cubes over night in ph 5.5 - 5.8ph water. the supplied ph graph only shows up2 6!!! how am i meant to go lower. also, the measuring beaker supplied doesnt have any mls on the side and it doesnt say how much the beaker holds lol. i tried a little tap water to 2 drops of ragent or watever its called and it came out the worst (highest on the chart) which is 7.6. wud i be better using Rating: 5