hello; I also do this from time to time. I use a garden hose when it is warm enough outside.
Hello; I guess my take on this results from 50+ years of getting away with the practice, some microbiology training and what I think I understand about the dynamic relationship of bacteria colonies.
First let me say I do take some precautions so as to not kill off too many beneficial bacteria (bb). I keep back some media and do not clean everything all at one time. I also keep a couple of sponge filter bases in the back of filters in the hope they will house some bb colonies.
Back in my undergraduate biology classes we made up culture media to put in petri dishes. Usually some form of agar-agar or blood agar. We would then apply various bacteria to the sterilized agar media in order to learn about the bacteria.
The bacteria would grow very quickly on culture media in a petri dish for a few days and then growth would slow and essentially pretty much stop. There would be a very large amount of nutrient remaining that the bacteria colonies could use but they did not. The explaination given was they sort of poisoned them selves because they had no plumbing. Sure they had a super abundance of "food" but no way to get rid of their own waste. The accumulation of the waste eventually was a toxin and stopped the growth of a colony. Some colonies might stop at dime size and others maybe would get to slightly bigger than a quarter.
Of course if there was some way a few of the bacteria got moved to another spot then a new colony would form. But in a covered petri dish there was no wind so that did not much happen.
What am I driving at? One thing that always seemed to me is from time to time the bio-media needs a good cleaning. This gives the bb a fresh place to colonize. Gentle rinsing in tank or conditioned water seems ok for a while but eventually it needs a good cleaning. I guess since I had been using a hose for decades before joining these fish forums I had some experience to fall back on.
I do not know how new fish keepers can judge these things. I am aware from reading posts the last nine years that the gentle rinse in old tank water is sort of a fish keeping "gospel".
I have also learned that the bb are sessile and stick well to the surfaces they colonize. I have not done any sort of check but do suspect that even with a hose rinse not all are removed. I do not usually scrub the media surface unless the build up is bad. I figure it is better to clean away the gunk that can smother the bb colonies even if I wash away some of the bb.
I learned this over time from experience of having fish tanks over the last 30 years.- not something I could explain to others "why" like you can- just that it worked.
I think this was because I learned fish-keeping not from others- no one I knew had fish 30 years ago- but from books. This is prior to the Internet, mind you. Books were your primary source for information, especially when everyone else around you only saw fish at aquarium stores. Which were few and far between where I lived.
My practices are often seen as strange: So be it.
MY biological media is always cleaned ( in rotation) with tap.
I change out a 1/4 of my bio-media per year for new.
Mechanical media is just that-mechanical. If you are using it as biological you are diminishing its purpose and efficiency as intended.
I do not keep my sponges until "they disintegrate". Have you ever noticed how they lose their ability to mechanically remove debris as they fibers break down? Why would you want to wait until they disintegrate- because you are using them as biological media.
These practices will make some fish-keepers on forums very angry that you dare to say you do them or believe they work.