I have just noticed my washing up sponge had quite a few little dots on it- looked like sesame seeds but were not! I don't know if they were bugs. I threw it away and got a new one out. Within a few hours there was a tiny dot on the new one. I can't see any legs and they didn't move. They were browny black. It's weird that one appeared even after I threw the sponge away. Any ideas?!
No pets, no. The sponges live under the sink, and I wonder if something has been embedded in them which grow and surface with the damp. But I might be being paranoid. There are tiny black specks in the new sponge, kind trapped inside it.
You don't say if the "spots" are moving. You may be dealing with mildew. A damp or wet sponge must have good air circulation around it to dry properly in order to avoid mildew. That includes the bottom (the part on which it rests). I keep my kitchen sponges in a wire basket that allows full air circulation.