Ursus-SUON
A tap water pH of 7.0 isn't too bad, generally more important is knowing what the EC/ppm is. If you are going to grow hydroponically I'd suggest getting and EC/ppm meter and a pH meter, or at the very least a test kit.
I'm currently using a Hanna Gro Check, which I like a lot, but probably the most robust and reliable EC/ppm meter I've used is the NZ(now Blue Lab) Truncheon.
If you know what your water quality is, you can make the first step of deciding of either going with Hard or Soft water nutrients.
Personally with mineral/bio-mineral nutes, I found it best to change the res once a week to reduce the chance of potential problems. Found that you could leave the res change for longer but the chance of nute issues increased.
I'd feed for 6 days a week, day 7 use water and additives(B-vits, Humic, Fulvic...). I liked to feed over a pH spread of around .5, so that if your target pH was 5.6, set the pH to 5.4 and let it drift to 5.9 before dropping it back to 5.4. For vegging I'd run the pH about .2-.3 higher than the target pH.
I'd check the water level at least once a day, if the temps are warm more often. When you top up the water, check the ppm and adjust it to what it was at the start of the week, maybe a fraction higher, then adjust the pH. Ideally check the pH at least once a day if the nutes aren't buffered.
Week on week look to increase the ppm, until you hit the peak feed strength(for myself about 3 weeks from the chop). If you are running a mainly indica strain, I'd suggest increasing the ppm by about 100-200ppm(700 scale) each week, for sativa strains 50-100ppm(700 scale). Read the plants, if it isn't enough add a fraction more, if it's too much remove some of the res and top up with water and adjust pH.
If you are looking for non-hydro products for dropping your pH, try using vinegar or food grade citric acid(bought a load from a home brewing company). You'll still need to know what the pH is, meter or test kit, so you don't drop the pH too much.
As both vinegar and citric acid are 'weak acids' they tend to need more to drop the pH and tend to have a quicker pH climb afterwards while the equilibruim is established. Hydroponic 'strong acids', Nitric or Phosphoric, usually need a lot less to adjust the pH and have a slower pH climb as the equilibrium is established more quickly.
Personally I like to use nitric acid during veg, and a combination of citric and phosphoric acid during flowering.
As far as I know, a number of hydroponic nutes have buffers in them so that very little pH adjusting is needed. A number of friends use Ionic nutes, and very rarely need to adjust pH and get decent results.
If you have Humic or Fulvic acid, then you could use this to drop the pH.
If you are going to do hydro,
hydrogen peroxide can be a very useful thing to add to your res. Helps to keep pathogens in check and keep the dissolved oxygen levels up.
