Not sure if you are into making your own compost, but I've been using this recipe for several years now, and with very few problems - such as damping off, etc.

Because my compost heats up, it is probably a lot safer than purchase of potting soils. If I do use purchased potting soils, I would solarize it, to rid any mold or fungus spores.

I use a mix of fresh screened compost and peat moss, about 2/3rds compost, to 1/3 peat. Because seeds have all they need to sprout - no fertilizers are needed until they grow several leaves.

As my climate is warm enough, I usually wait until seedlings are planted out and established before I begin to fertilize.

HOpe this helps.

P.S. I should think vermiculite would also work, but because I have fresh compost available, this is what I use successfully. In the past, I had a problem with bagged potting soils, however, due to damping off.

BEJAY