MY experience has been that rthere is plenty of bacteria. I have totally emptied my 100 gallon Skippy, save nothing and NEVER a problem! There must be plenty of the good stuff in the pond. I had Pond vac by OASE never used it. Tried to sell it here, but no luck. I sold it 2 months ago at a koi club meeting .
If Ineed the pond vacuumed, I call a guy!