Are sponges dirty

Keep them fresh buy boiling them once a week or soaking in mild Bleach solution.

You have to clean your sponge. You can microwave it.

You can also run them through your dishwasher when you run your dishes each time or run it through your washer with your white things & bleach! Hope this helps!

It depends on what you have cleaned with the sponge. Don't clean a toilet and then use the same sponge on the dishes. Have your bathroom sponge and your kitchen sponge. You can put sponges in the dishwasher which does a very good job of keeping them clean and removing mildew smell. I always squeeze my sponges out and put them on my kitchen window sill to dry. If you leaving it sitting in the sink all wet, it will get nasty pretty quick. Don't forget that most dish soaps these days are antibacterial so that helps.

Sponges are prone to have bacteria and should be changed every month or when they start looking grungy

they are loaded with bacteria

I microwave mine daily.

Sponges are terrible. I would switch to netted dishcloth cloth.