If you use the r/o you will need to add Cal/mag back in.
DO NOT DO THIS !!!
Nuthin' personal SH, so don't take it that way. It is just not good advice,
especially with GH 3 part. GH makes a specific Micro formula for hard water. Take RO, add Cal/Mag and you now have hard water. Add normal GH Micro to this and you end up with too much N, Ca & Mg. If you are running GH and you
think you have too little Ca & Mg in your res (which you don't), you can rectify this with pH manipulation.
I sound like a broken record with a couple issues in multiple threads. One of them is Cal/Mag and one of them is the pH chart you have as your avatar. So, let my same 'ol tune begin again.
The Cal/Mag craze started a few years ago.
Botanicare's PBP had a lot to do with this. It is low in certain things, like Mg and some other things. This deficiencies in their formula become very apparent when you run RO water with them. If you are using RO water with PBP, you
must also give Botaincare money for Cal/Mag+.
People like PBP because it is the easiest solution to people's desire to run organic hydro (even though it is not quite 100% organic), so it became popular despite its flaws in providing an optimal nutrient solution for Sweet Lady Jane. And with it comes the necessary use of Cal/Mag+ to make up for the lack of Ca & Mg in their base PBP formula.
And then the MJ forum echo chamber began and everyone began talking about Cal/Mag and how you needed to use it with RO, etc. Unfortunately, a lot of the people involved in the echo chamber were not overly experienced growers, just people that read some internet posts and began repeating them, slept in a Holiday Inn the night before and crowned themselves as experts.
GH 3 Part does
not have that problem. It has all the Ca & Mg you need for mj, even with RO. In fact, that is why they make Micro for hard water. Use the RO filter. You can attach that filter to your sink with a simple adapter, so it is easy to use. The big advantage you will gain when starting with an RO water supply is you avoid the alkalinity of tap water. Alakalinity refers to the resistance of the water to acids and pH changes. The higher the alkalinity, the more acid you need to pour in to drop the pH.
The importance of this is that after you mix your nutes (nutes are acidic), your starting pH will be too high as the alkalinity of tap buffers the nutes. If you mix GH 3 Part at recommended dosage in RO water, you start at the most optimal point, pH wise. This is around 5.1-5.2. If you use tap water, because of the alaklinity, after you mix, your starting pH could be higher, like 5.5-6.0, depending on your tap water at your location. That is in addition to all of the crap and excess Ca & Mg in tap you don't want to expose your plants to.
Speaking of pH ...
... don't refer to that chart in your avatar. I actually remember when St0ney created that chart on the old HC boards. It was a decade ago, well, probably slightly over a decade ago. Because it was posted on a weed forum at a time when there really weren't any other charts floating around, it got picked up and circulated. The B&W chart you see (I think it is in a sticky here) is the one to look at and refer to.
The B&W chart was put together by scientists, not a stoner who was having problems with his grow from an inappropriate nutrient solution in his res like St0ney was. St0ney was trying to be helpful, but that chart is a result of problems he was having in a hydro grow - so it was
not made by someone who i woudl consider an expert, certainly not at the time, evidenced by his problems.
As far as your setup with the tray filled with hydroton and rockwool sitting on top, although you can make some comments in the 'pro' column as far as doing it that way, their are also 'cons'. From my experience, the 'cons' outweigh the 'pros'. I also try to avoid, whether dirt or hydro, locking my plants into place, for one. The benefits you gain from being able to move your plants around in the tray if they are in individual pots can be pretty big. And it can be a critical point in saving your crop if you run into problems - of which many can arise.
Nutes do have a shelf life. Organics more so than inorganics, for sure. I don't know at what point GH 3 part will break down, as I have never sat on them for a year. Contact GH tech for the most accurate time frame. Managing your res is a big topic in of itself, but if your wallet can handle it (shouldn't be bad with GH and a res your size), instead of adding pH down, replace your res after the pH has climbed to 6.2 or so. This could be 1-3 weeks, depending on strain and growroom conditions.
