I have used the coir bedding from pet smart... It will work just fine... I have more often used the stuff from the hydro/grow shop... To my knowledge, there is only one brand that infuses trich into their mix... Stay away from the "Canna" brand and you should be fine... I have used a few different ones from the grow shop with great success... The stuff from the pet store is perfectly fine also... I think it is a little cheaper to get the kind that is pressed into blocks rather than the bag of loose coir but I am not 100% on that, just pretty sure...
I typically eyeball my substrate mixes but if you are going to add vermiculite, I would probably mix it 1:1:0.50 or 1:1:0.3... corn:coir:verm... The substrate mix is really forgiving though, I would not worry about measuring it out, if you get close to those ratios, you will be in position to get acceptable results baring some other, unforseen issue.
Edited by PJammer24, 13 December 2020 - 03:29 PM.