What you can do - get African Violet soil in a store - and add 1/3 perlite to it, better coarse. This mix is light and doesn't have a lot of nutrients. Get some AV fertilizer too - something like Peters African Violet Specialty fertilizer - and add to your water 1/8 - 1/4 teaspoon per gallon. They shouldn't stand in water - pour water out of saucers 30min after watering. Your Hoyas will appreciate this fertilizer too.

If you want to know more about how grow gesneriads - you will enjoy checking gesneriadsociety.org and gesneriads.ca

Good Luck

Irina

the standard mix for gesneriads is peat, perlite, vermiculite 1:1:1, plus to be even better - a bit of crashed dolomite to off the acidity, microelements and horticultural charcoal. It is hard to say how much dolomite because the peat moss acidity can be let's say 3.5-4.2 Ph and you want to end close to neutral.

You can order premade mix from vendors - look at avsa.org or gesneriadsociety.org "vendors" - just to know how what it should look like.

It depends how you grow them - I grow practically everything on wicks- so I need light soil. If you bottom water them - you can go heavier - - more vermiculite than perlite.

A very good way of growing Nemathanthus and Columneas - is in Oyama pots. I add even more perlite to the basic mix for Oyamas. These things make watering really easy.

Irina