I don't like the sounds of it. If it was me and I still had the receipt, I'd be returning it. Maybe someone can chime in as to whether or not boiling water poured throughout would make a difference.

Moss growing on top of the soil in containers sown is OK with me, but mold... YUCK!

I wouldn't use it. The mold will smother and rot your seeds I think.

Ok, thanks guys.

Did you wet it during the process of prepping it and then close the bag back up? If not sometimes brand new bags that are pre-moistened can get the fungi working on their own; especially if it was stored someplace warm. In your case I'm thinking it was just the natural fungi (the good guys) as well that continue to break down decaying matter. Was it white, pale yellow or pale green in color? I get this sometimes during winter months shortly after watering on the surface of my houseplants because the surface of the soil does not dry out as quickly. As soon as I scratch up the surface and invite more air it's quickly gone when the conditions are no longer favorable....in days.

If it were me, I would open the bag and toss the mix around inside; leave it open for a few days and see if it disappears. Then I would use it.

Vera

Do what Vera says; I have white mold in my bag of Miracle-Gro, most likely because the bag has been closed up in the warm apartment. I opened up the bag, mixed the soil around and closed the bag again, leaving a part open so air can get in. The white stuff is gone.

PV

Maybe you could bake it. Sometimes I use my composted garden soil to plant seeds in. I bake it for about an hour at 300 degrees. It kills all the weed seeds and insects. Would probably kill the mold.

What's important to understand here is that baking the soil would be a waste of energy in this case; plus it kills the good fungi that help in keeping the bad guys under control. It's kinda like the human body without white blood cells you can fight infection.
This type of fungi has one job and that is aiding the process of decay. They will not attack living tissue. Sometimes you will notice this same thing growing in your WS containers placed in a sunny warm location if the medium contains pieces of bark and sticks like Miracle Gro does. Seedlings germinate and grow just fine. When it happens to me I just make more vent holes (or remove forever; depending) and it goes away :D

Vera

You can sterilize soil in the microwave. Take out stones, big particles of garden debris. Couple cups in a glass dish, nuke on high for 2 minutes. Let cool. No more mold, kills dieases and insect eggs. You can do this with your own soil from your garden, to start seeds. Sterilizing soil using heat has been done for many years.

I like the idea of letting the soil dry and air out for a few days--spread it into a few large containers if you can. Then why not to a quick germination test indoors, with something that should come up fast--beans, radishes, tomatoes, or lettuce or similar. That way you can feel confident that your soil is ok.

A couple of years ago I baked soil to sterilize it for indoor seed starting. I baked it for hours, trying to get it up to boiling temp (it was wet soil). Then I read on the internet that I didn't need to go that high, and in fact, if I let it get above some temperature--which I had--that the soil was going to be ruined, and not to use it, blah blah blah. That didn't make sense to me, and I hated to waste that big pot of soil. So I grew some tomatoes in the soil as a test--they were fine, and I used the rest of the soil.