Heya, I'm hesitant to say you've got aphids for 2 reasons:
They are to put it mildly a highly unusual guest in an indoor garden. I've only ever seen them indoors on my mom's hisbiscus, that she leaves out all summer. Possible, but uncommon.
They are also green. They make a sticky mess, too.
Do they look plump and round, or like slivers, or like tiny flies with tiny wings? Are there webs? Can you see anything that looks like eggs under the worst affected leaves? Use a magnifying glass to check.
One of the more common indoor pests is thrips, and what you're describing is something I'd check for thrips first. The larvae look like tiny cream colored splinters of wood. They leave pale munch marks from oval to elongated shapes. Mites leave tiny dots, for comparison.
Thrips are so easy to get rid of indoors, so if that's what you have, lucky you. Yes, diatomaceous earth is one weapon. Sprinkle some around the base of the stem. Now go find some disposable plates, the foam ones are easiest. Cut a slit from edge to center, then cut a hole in the middle about 2x the diameter of the stem. Make sure the plate is wider than thepot. Slip it on, being sure to prop it up on toothpicks or something so there's air flow under it, tape the seam, and just be sure to keep the floor vacuumed.
What you've done it disrupted the life cycle. The winglesslarvae cause the mist immediately visible damage. They eat leaves, get fat, and dropto the soil surface to pupate into winged adults, which then lay eggs in the plant tissue and restart the cycle. If the larvae can't find dirt, they die. Hence the plate.
If you can get pics of the bugs and damage, post em up!
