[WaterLife]

The reason you don't want to wash biological media in tap water is because the chlorine in the tap water will kill the beneficial bacteria. You could use R/O water or new/clean treated (w/ dechlorinator) water.

The tank water is just more convenient and a known safe means of washing the media without killing the beneficial bacteria, and it gets clean enough, plus it sort of still leaves some "food" near the beneficial bacteria's "home".
I believe the beneficial bacteria can also be killed off with drastic temperature changes (of the water) as well.

However using a bucket of clean/new treated water, you do run the risk on having the chlorinated water in the bucket not fully removing the chlorine yet when you go to rinse the media, so it's still risky that you might kill some of the BB. It can be done though, I just personally don't want to chance it.
I guess the same can be said about the new water from a water change into the tank not yet fully "de-chlorinating" before turning the filters on. I usually let the new water sit/mix a while before turning the filters back on and/or add a little extra dechlorinator/water conditioner.

You can wash mechanical and chemical media with tap water since they usually (can be instances where they do house a significant part of the beneficial bacteria colony) don't have any significant source of nitrifying bacteria. The nitrifying bacteria in the tank water and all through out the tank is minimal as well which is why it's not worried about much.

 

[Argus]

The reason you don't want to wash biological media in tap water is because the chlorine in the tap water will kill the beneficial bacteria. You could use R/O water or new/clean treated (w/ dechlorinator) water.

Thermal shock could also be a consideration.

When cleaning a filter you mainly want to remove the solid waste. You are not trying to chemically clean it. So, dissolved chemicals in tank water are not an issue. Rinsing the sponges from a Fluval 206 in a container of old tank water turns the water opaque brown. So, yes, tank water is much cleaner than the filter.

 

[PlantedRich]

I would guess the instructions so commonly given are due to the common mistakes new folks may make. Saying to use tap water is wrong as they may go off and leave the media in a bucket of chlorine treated water for a few hours which will kill a lot of BB. Say use treated tap water and they may use HOT water. So as a dodge for a number of ways to screw up the process, "old tank water" is one which will cover if they leave it for hours or any number of other ways to mess things up. Once you find what is required and what is going to harm you and your tank, you are likely to move some of the common advise a bit further back in your mind. Watch a bit of the tube advice and you can see all kinds of ways that things can be done---but not all are safe for the newer folks. Knowledge is power and once you achieve some of that knowledge, you can then begin to find shortcuts. But there are two ways to gain that knowledge. Killing your fish is just one of those ways so it is better to use the safer advise until you know the why and where of shortcuts.

 

[Kobey]

Fair enough.

I suppose too that since the BB live off ammonia and nitrites washing the filters in water that contains more as opposed to less of those would also be better.

Point taken...used water it is...I will flush that analogy.

 

[WaterLife]

Just to mention, I have heard of too high of ammonia levels also killing nitrifying bacteria (I.E. dosing way too much ammonia when cycling tank).

As mentioned though, the rinsing water doesn't have to have ammonia/nitrites, you just don't want to use water with chlorine in it, hence Reverse Osmosis water and treated water are fine to use (both of which have no ammonia/nitrites -usually-).

 

[Kobey]

how high would ammonia have to be to kill of the BB?...I'm thinking if that happened way worse it also going on.

 

[Diana]

There are many species of microorganisms that live on ammonia.
Different organisms thrive at different levels of ammonia.
The species that thrive in a sewage treatment plant or in the muck and mud of a feed lot are different from the ones that thrive in our aquariums.

Optimum level of ammonia to grow the bacteria, for them to reproduce at the fastest rate is anywhere from about 1-5ppm.
Lower than that and the food is too infrequent, so the bacteria do not reproduce so fast. They live just fine, though. Higher than 5 ppm and they do not grow as fast. I do not know at what level they start dying, though. Just that other species are more prevalent when the ammonia level is higher. The other species are better at reproducing when the ammonia level is higher.

The beneficial bacteria live on the surfaces, in a biofilm, a material they and other microorganisms make. It is a complex channel that allows the water to flow through and around the organisms. A quick rinse in chlorinated (chloramine or chlorine) probably will not kill the organisms- the water with the chlorine comes and goes so fast that very little of the chlorine contacts the beneficial organisms. As noted above, though, a beginner might do all sorts of things that could kill the bacteria from longer exposure to the temperature change issue, or adding soap and probably many more things. Safest to say 'Clean the filter media in water removed from the tank for a water change'.
Then you know the water is at the same temperature and water chemistry that the bacteria are already used to, so won't be killed.
It is probably just fine to give the media a quick rinse in tap water, hot (as long as you can still touch it, and handle the media) or cold. I generally find such a quick rinse is not enough to properly clean the media, though.
It is entirely safe to rinse the media in water you have prepared for the water change. Such water should be the right temperature, and close enough to the water parameters in the tank that it will cause no problems for the bacteria. But then I am throwing away perfectly good water that could have gone into the tank. I would have to prepare extra water, knowing I was going to throw away a few gallons.
Best is to clean the media in used aquarium water, then use that water in the garden. Gets the filter media as clean as it needs to be.

 

[theatermusic87]

No reason you can't use treated water... Same with tank water, and add long as your tank us established you can even rinse in untreated tap water as long as you don't go crazy. Chlorine and all, the bacteria will bounce back very quickly

 

[brandon429]

Lots of old school aquarists rinse in tap water it absolutely does not kill off your bb when using it as a rinse

-a low rumble begins-

To begin the discussion post these details:

What is the generalized aerobic bacteria colony counts coming out of your tap at this moment (consult local water treatment authority for free report)

If tap water sterilizes and bacteria require aquarists to add their feed or they can't get it any other way, why does the chlorinated tap spit living bacteria...how were they getting fed as they existed in pipe scum that had 120 degree water through it daily for decades?

What general grouping do nitrifers fall in?


What insulators are bb found in, or do they present as just single bacteria surrounded by nothing ready for the zap?

What is the contact time established for tap water to sterilize a container of water against all forms of mixed aerobes?

Even on my reef I'll blast rinse the sandbed in tap water sometimes. But I re rinse in distilled or fresh mixed sw just to remove the tap contaminants and to ensure delicate benthic creatures won't encounter any chlorination. On FW setups you can rinse media in tap and then briefly in clean FW as a follow up, or not even post rinse it won't matter considering tank dilutions.