Rinsing the media in discarded tank water removes built up crud not bacteral colonies Vacuuming the substrate does not remove nitrafying bacteria it does remove built up crud
As a matter of fact, bacteria live in that crud. This detritus has a great surface. It's much bigger than the bio media or the gravel. Bacteria don't just live neatly on the surface of the media and wait for food to drift by, they live in the crud. That's where they extend their colonies to. Washing it away removes a substantial amount of bacteria.
beblondie said:
even if damaged the size of the colonies double every 24 at 77F and replenishes itself quickly
That's in theory in the lab. You remove their food and their colonies. It'll be a while before they are back to normal. If you wash the gravel and the filter media, you damage both main bacterial habitats. Their activity comes back to normal much easier when only one of the two is diminished. Not to help to seed the new colony, but to maintain the level of bacterial activity at a higher level. As I said, in the given situation I would not want to risk a nitrite or ammonia peak in those few days that the bacteria recover and repopulate. Maybe that's just me. Better safe than sorry. His fish don't die at the given nitrate levels, I see no need to risk anything here by panic-driven mass-clean-ups. One week in between won't hurt anybody.