what is the best water to buy for a bubbleponics setup?(ie. distilled, spring........

right now i am using distilled water and it had a ph of 6.0. but i am starting to have a sodium issue on top of my lava rocks. could it be caused by my fertilizer or what. what can i do to fix it

Distilled water should have a pH of 7.0. If it doesn't I question whether it is distilled. If I were buying water I'd buy reverse osmosis water which you can get from self serve machines at many supermarkets. or you can get your own ro filter. Assuming your nutes are the only thing you are putting in there, they must be the cause.

reverse osmosis is what I use