I used to add perlite to Jiffy Mix or Promix and it worked very well. All I need to do is try to remember the ratio of what I used since no way was I going to pay what anyone of those nonmixed products asked for price wise.
BUT when mixing up stuff for seed germination I used the best I could find and I discovered what Charlie,my farmer friend used and that was Farfard. I think I spelled it correctly.
Nope,I didn't spell it correctly,here is the proper spelling
https://www.google.com/search?hl=en&....0.DASlqVVtgtM
No seed germination,no worries about using anything for any purpose the way I see it.
Carolyn