A photo would be cool! Slime molds are pretty interesting.

Fuligo septica, if that's what you have isn't a very harmful pest unless, as you say you have allergies, or asthma. Once it starts dropping spores there's no way to know if it will spread to other places in your home. thy won't just start growing anywhere but if they find just there right environment to start up then they will.

If you need to repot it, do it outside if you can. you probably won't be able to spray it with something to kill it.

you can carefully scoop out the top 1/2-1" of soil with a spoon and then spray the surface with weak vinegar solution. then check and repeat until gone.
bark often contains mold spores.

well, i had it and did spray (on alocasia poly - doing totally fine) and it went away.
the weak solution: 2tb per gallon of water applied as spray on the surface is not going to do much to PH of soil. the mold is usually just on the surface. no need to drench.
also i then watered in neem solution, which is also recommended. i had to spray a couple of times a few days apart. i have quite a bit of fine bark in the mix . even though it's orchid bark and supposed to be sterile, guess some spores survive anyway.
read that it happens when humidity is very high and medium is damp. i was waking up my tubers in a kind of propagator box - so 100% humidity and warmth did it, i suppose.
http://www.ehow.com/how_7319907_kill-slime-mold-yard-organically.html

How long have you had this plant? I wonder if you are seeing salt/hard water deposits on the surface?

Well, my initial reaction to seeing the stuff was to freak out and scrape off as much as possible because I knew I *did not want it*, whatever it was. Unfortunately, this makes photo documentation difficult. Sorry, I was not thinking long term. Since all members of my family appear to be unanimously anti-giant amoeba, I will be hauling the thing outside to repot on Saturday, weather permitting. I will take photos then. I can tell there are some more spore deposits down the sides of the soil inside the pot. I believe all I am seeing is the final stage of life, where it dries out and forms the spores. It has a dry, spongy texture and crumbles easily into lots of tiny little balls. It looks just like photos I have seen online of slime molds.

Well, I still have not repotted my slime mold infested peace lily because it is huge and I am lazy... but this morning I started to water this small snake plant and a glob of goo popped up to the surface. Ugh! I am doomed. Doooomed! Halloween came early this year.

{{gwi:101569}}

That doesn't look like anything I've ever seen in a pot or on the ground before, like more slimy than slime mold. Is there any possibility it came out of the watering can, like something fell in there? Pic enlarges to great, huge size, but unfortunately that part is not in focus.

I can't picture how this went at all: "I started to water this small snake plant and a glob of goo popped up to the surface." But I am curious to hear more.

I'd have to pull that plant out of the pot and see what's going on, curiosity would demand it. Do you want to do that? Take pics? Can you add a pic of the stuff in the peace lily pot too?

If it really did come up from inside, I'm thinking it was already still quite moist in the pot. Sans that aren't baking in the heat/sun outside really need to dry out between drinks of water. It looks like the pot is sitting in a larger bowl or bucket. If water stays at the bottom of that, the roots of the Sans could rot. I would water at a sink so excess water has dripped away, then set on something that protects furniture (and/or sanity) if needed.

You were right. Something had congealed in my water jug. I'm not sure I want to contemplate how. I guess I can relax somewhat now, but I still need to deal with that peace lily.

I've been there, it happens - it looked familiar. That's preferable to weird, icky alternatives, IMVHO. That in the Sans pot will dry up and be like it never happened.

Pic of PL?

I have a house plant not sure what kind it is, but I've had it since it was super small, about 2 years. My kids noticed this on the surface and from what I can gather it has slime mold. I took some off the surface last night and it's back again today.

Soil appears to be very mucky.

Al