I have a bag of
foxfarm ready made coco 70/30. I am planning to add 30 percent extra perlite to that?
I use FF Cultivation Nation and I like it. Don't add perlite to it, 70/30 is where you want to start.
For nutrients, I have a basic coco A/B set to feed in equal amounts.
Canna Coco is good. Gen Hydro is also good. Whichever line you're using, my advice is to lookup the manufacturer's feeding directions and follow those ratios. You will see a lot of garbage feed charts floating around without any shred of scientific method behind them, and you want to avoid those.
I have no
calmag, and need a good coco specific type?
Canna Part A specifically already has a high level of calcium, you will likely not need to add any additional
CalMag should you follow their directions. It's always good to have some on hand however, because it's a tool you can use to help correct certain problems. Fox Farms and Gen Hydro both have good
CalMag products and will probably be the easiest for you to find.
You do not need to pre-flush or buffer that Fox Farms mix, it comes to you already buffered.
As for watering in soil, I have used anything but tap…..reverse osmosis, purified, spring, or distilled….whatevers on sale.
There's different reasons for using different kinds of water but unless your tap water is very bad it's probably fine to use. RO systems are expensive and produce a significant amount of waste water so I generally don't recommend them unless your water is
very bad. If you really need to run your water through something, you can go distilled; you can get a distilled water maker for about $50 of amazon and it wastes 0 water in the process.
Should I buy a decent ph pen set and start PH’ing my tap water with coco?
Probes might be the most important tools that you have here. Yes, you will need a good pH meter, but more importantly you also need a good EC meter. Get something that measures actual EC (either micro or milliSiemens) and not something in a derivative scale, like PPM or TDS. My opinion here is that you don't have to spend a fortune, but if this is something you're going to get into, you want to get something good. I have an Apera Instruments AI316 5-in-1 and I highly recommend it. You can get a whole kit with case and calibration solutions for about $150. I got it after my cheap pens fell out of calibration and trashed one of my grows in flower.
Will hydro nutrients and supplements, work in coco?
Stick with nutrient lines that are advertised as usable in coco; they don't have to be
exclusively for coco, e.g. Gen Hydro is usable in varying media.
Can I use any of my organic soil nutrients in coco?
There are ways to use organics in coco but coco itself is an inert medium; it does not have any of the living biome that's generally required to utilize organic nutrients. It's a path you can go down but a more advanced one that you probably shouldn't worry about just starting off.
Finally, do you flush coco plants or feed them up to harvest?
This is probably the most opinionated question you asked, which to me says that there's far from one right answer. Some people feed until the end, others will flush for a varying number of days, you can get results either way so maybe this one is for you to figure out on your own.
I think the biggest trap new coco growers fall into is seeing a physical medium that looks like soil and following their instinct to treat it as such. Coco is very much a hydroponic endeavor, closer to a DWC than soil. Most to all of what you learned in soil will not be relevant here so don't try to fall back on it.