PH for organic coco grow?

6.2 is good idea. give you a bit of wiggle room. 5.9 is to low if it goes lower your entering lockout range IMO. Coir its self is around PH 7. I have grown with amendments and always aim 6.2-6.5 to low and it gets weird. If you don't have a good brand of coir it needs to be rinsed and buffered, can google this if you are unfamiliar with the terms. I like CANNA brand as they treat it well. You will also want at least 30% perlite in the mix as well. The coir you get a homedepo for 9$ is the stuff u gotta worry about. Useing RO water is not great. save it for drinking. RO will also damage your PH probe, their needs to be something in the water or it becomes very aggressive and will eat away at things. its why all RO taps use plastic pipes, only thing that will not degrade. If you already set on it. Don't PH probe the water, just add in a bit of PH down, it will have issues reading it. Same with PPM/EC pens. pure RO fucks em up. Try not to use metal items and only plastic as well. Biotabs look a lot like dry amendments but in little pills. You will want to not get any runoff with em to avoid leaching the soil. but with coir a bit of runoff can be good. Might need to schedule a flush from transition of veg to flower to avoid any issues. Microbes will be your friend boost the medium with tons of them if you don't already. Amending in moretabs might be difficult with think root base, can try blending them up and into the water then in. I like using wetting agents to break surface tension of water. Yucca is one such one. Water in slowly to avoid dry spots. Good Luck!

Organic grows in coco 5.9 and then allows the pH to drift between the upper and lower ends of 5.6-6.4. This is optimal for the microorganisms and will keep hydrogen activating in the medium, critical for organics.