Aquarium fleas! Haha! Annoying but harmless, the fish will eat them but they won’t spread to your house. If you have driftwood sometimes they come with eggs/larva inside that you don’t see before it’s too late.
Couple things you can do:
1. If you have driftwood, get rid of it and get a new one and clean/vacuum your tank, or just completely start from scratch but you would need a temporary home for your existing fish and that would just stress them out.
2. Get more fish that will eat them and hopefully eventually they’ll dissipate.
3. There may be some chemicals to throw in there that will kill them as well as any existing eggs/larvae but I don’t know how harsh it is on the fish.
Let me know what happens. Good luck!