Overdose probiotics?

Apparently it is not really necessary to eliminate all bad bacteria, fungi, etc. that live in your gut. 100% elimination probably isn't even possible anyway. It is recommended to just make sure the bad bacteria are in proper proportion to the good bacteria. I remember having read somewhere 80% good, 20% bad bacteria, is the proper proportion. Is this all true?

If so, I suppose you can actually 'overdo' your anti-candida regimen (which actually also is 'anti-' a lot of other (good and) bad bacteria, fungi, parasites). Would it be 'bad' to have for example 100% good bacteria (, fungi, etc), and 0% bad ones?

I have been and am taking quite some high-quality probiotics; my question: is it possible to 'overdose probiotics' and get adverse effects?