I recently had it suggested to me to use some premixed bonsai soil and mix it approx 1:1 with coco peat. This was a general recomendation but specifically it was for a small Ficus ginsing that I had. Is this a poor medium, if so why? Will it work temporarily?

Premixed bonsai soil does not really go into details. There is no such thing as "bonsai soil".
The soil depends on lot of things.
-species
-your effort you would like to put in to fertilize and water the tree
-climate
-pot size

It it's a house plant I'd use ordinary potting soil

It's Hoffmann bonsai soil mix to be specific. I'm pretty involved with watering and fertilizing but I'm trying to be as efficient as possible and get the best growth

from what ive seen, cocopeat is used mostly for cuttings and seeds because its great at holding water. ficuses are tropical, so they like lots of water, but peat is not good for draining. i wouldnt use more than 50% peat in any mixture, especially if you are able to water it daily. There is no magical mix, but you do want good drainage, some sort of coarse material that allows water to freely flow through and out of the pot, which brings air to the roots.

hello, I would recommend using this soil mix. www.amazon.com/Bonsai-Soil-Mix-Professio...bonsai+soil+mix&psc= . this soil has worked great for all my trees and is not that expensive.