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6.9. Afspoelen met kraanwater

Foto van auteur

Auteur : David Bogert

Gepubliceerd :

Tijd om te lezen :
6 minuten
Difficulty : Level 6

Excerpt :

Probably the worst thing one can do to an aquarium filter is to put it under running water. Running water will rapidly clean out ALL the beneficial bacteria.

There is the constant myth on social media that one needs to clean the filters and filter media in tank water to prevent the chlorine in tap water from removing and killing all the beneficial bacteria. This is simply a false myth.

Otofarynx lithobates Walteri
Otofarynx lithobates - Walteri

Synopsis of Test

Multiple replicate scientific experiments were carried out with controls. These studies looked at cleaning sponge filters with both chlorinated and unchlorinated water.

Ze stelden vast:

  • Cleaning a newly established (months) sponge filter under running unchlorinated well water OR chlorinated water removed virtually all the beneficial bacteria
  • Cleaning a newly established (months) sponge filter in a pail of unchlorinated well water, aquarium water OR chlorinated water left significant amounts of beneficial bacteria in the filter.
  • Cleaning a long established (years) sponge filter under running unchlorinated well water OR chlorinated water left significant amounts of beneficial bacteria in the filter.

So you never want to clean a relatively new filter media in running tap water, even if it is unchlorinated well water. You can get ammonia spikes.

Aquarium fish Cynotilapia Pulpican “Likoma”
Cynotilapia Pulpican “Likoma”


The idea that cleaning a filter in chlorinated water destroys the beneficial bacteria was tested. The test proved beyond any doubt that chlorine levels even two to four times what is found in tap water have no effect on the beneficial bacteria.

Test apparatuur:

  • Tien 19,93 liter oranje Home Depot emmers
  • Luchtpomp en luchtslang
  • Vier minisponsfilters die vier maanden hadden gedraaid
  • Vier doe-het-zelf Poret Sponsfilters van 20 ppi die vier jaar hadden gedraaid
  • Eén minisponsfilter dat nieuw was
  • Aquarium grind
  • Clorox bleekmiddel
OB Aulonocara
OB Aulonocara


Op vier sponsfilters werden in totaal vier maanden lang verschillende testen uitgevoerd. Deze vier filters hadden een complete verzameling nuttige bacteriën. Een andere set van vier sponsfilters kwam uit lang bewaarde kweekbakken. Deze sponsfilters waren 20 ppi Poret sponsblokjes die al minstens vier jaar en misschien wel langer werden gebruikt.

These eight sponge filters were then cleaned in tubs of water. The tubs were filled with well water to about three inches in depth. The water in the tubs was conditioned with four levels of chlorine: 2 ppm, 1 ppm, 0.5 ppm and no chlorine.

One bucket aquarium was set up with only about one inch of aquarium gravel in the bottom of the bucket and no sponge filter. This bucket only had an air stone in it. This was the “control” and was designed to test the hypothesis that substrate acts as a biofilter. Another “control” was set up with a new min sponge filter that had not been cycled or cleaned. That gave ten buckets.

De filters werden vervolgens in hun respectievelijke emmers gedaan en er werd een tijd tot cyclus test uitgevoerd. Om de drie dagen werd acht ppm ammoniak toegevoegd. Het ammoniakgehalte werd gemeten na drie dagen draaien en daarna elke drie dagen, vlak voordat er nieuwe ammoniak werd toegevoegd.

Aquarium Fish Cynotylapia afra Chitende
Cynotylapia afra – Chitende


Dit is het resultaat van de test in ppm ammoniak:

SponsChloorgehalte3 dagen6 dagen9 dagen12 dagen15 dagen
4 maanden minispons242000
4 maanden minispons124000
4 maanden minispons0.582000
4 maanden minispons042000
Nieuwe minisponsNA>8.0>8.04>8.04
Controle Geen filterNA>8.0>8.0>8.0>8.0>8.0
Testschema van spoelfilter in chloorwater

This rather conclusively proves that chlorine does not affect beneficial bacteria. The level of chlorine found in tap water is normally 0.5 to 1 ppm. So this tested levels that were two to four times normal and there was no problem.

Further testing was done on this topic. This testing can be found at these links:

6.8. Grondige reiniging

6.8.1. Thorough Cleaning Test

Aquarium Fish Cyphotilapia Frontosa
Cyphotilapia Frontosa


From Swiss Tropicals, the supplier of Poret Foam:

Het maakt niet uit of je koud of met chloor behandeld water gebruikt! Het vaak herhaalde idee dat dit proces alle filterorganismen zou doden is onzin, omdat de residuele chloorconcentratie in drinkwater te laag is om ze allemaal te doden. De micro-organismen zijn goed beschermd in het slijm van de biofilm.

Swiss Tropicals

Prime Time Aquatics has a video where they rinsed their many sponges in chlorinated tap water for years. Not one ammonia spike.

Elsewhere we calculate one part per million in one gallon (3.785 liter) is 0.00363 grams. Lets say we wash the filter media with ten gallons (37,85 liter) of tap water containing the typical chlorine dosage, or 0.5 ppm. This is 0.0181 grams of chlorine going through the filter media.

Any decently clogged filter media will have at least 10 grams of bacteria and organic matter in it capable of reacting with the chlorine and being killed. 0.0181/10 = 0.00181 or 0.18% of the bacteria will be killed. I.e. running filter media under tap water containing chlorine will kill roughly two tenths of one percent of the bacteria in the filter IF CHLORINE KILLED INSTANTLY, which it decidedly does not do. Hardly something to get one’s knickers in a bind over.

Aquarium Fish Cyprichromis leptosoma Chituta
Cyprichromis leptosoma – Chituta

Chlorine (and all disinfectants), take time to work. The lower the concentration the more time it takes for chlorine to kill ANY bacteria. So the chlorine levels in tap water (0.25 to 1.0 ppm typical) take an hour or more to kill bacteria. So a rinse done for thirty to sixty seconds does nothing, not even two tenths of one percent.

A study was done on how long it takes chloramine to kill nitrifying bacteria. The study was: “Bacterial Nitrification in Chloraminated Water Supplies” David Cunliffe, 1991. This study showed chloramine at the concentration normally found in tap water takes an hour and a half to kill even tiny amounts of nitrifying bacteria. This is hardly the typical 15 seconds or so it takes to clean a sponge filter.

If chlorinated water killed bacteria instantly then all hospitals would have to do to sterilize surfaces would be to wipe the surface with tap water. Instead hospitals wipe surfaces with disinfectants in very high concentrations (like 70% isopropyl alcohol or 500 ppm chlorine).

The actual “problem” has to do with simply cleaning the filter media. As tests in the links above reveal, thoroughly cleaning filter media which has only been established for four months removes a significant amount of the beneficial bacteria. More than three squeezes of a sponge filter and the sponge needs to be recycled.

As a result, hobbyists are always coming on social media and saying that they killed their beneficial bacteria and caused an ammonia spike by cleaning the filter under a stream of chlorinated tap water. It wasn’t the chlorine that removed their beneficial bacteria, it was the thorough cleaning under running water.

Oreochromis mossambicus Hawaiian Gold Tilapia
Oreochromis mossambicus – Hawaiian Gold Tilapia

Also, it appears that squeezing and swishing a sponge back and forth in a bucket of water removes far less beneficial bacteria than does putting the sponge under running water and squeezing it. And sponge filters which have been operating for years are very difficult to clean of all their beneficial bacteria.

Also some individuals use their sponge filters as only mechanical filters, thoroughly cleaning them once a week under running tap water. These hobbyists rely on thing like the surfaces in the aquarium to house the vast majority of their beneficial bacteria. This is a perfectly acceptable use of sponge filtration. But I would not attempt this on a heavily stocked aquarium.