# Stagnant Water Left in Canister Filter - Dangerous?



## razak101 (Apr 3, 2021)

Hi everyone,

I recently picked up a used fishtank of cichlids from a hobbyist. It came with a lot of great equipment and a tank full of cichlids and plecos.

When I first set it up at home I couldn't get the Fluval canister filter going. It just wouldn't kick on. So I left it sitting as there was a secondary canister filter that was still working. Finally, after about 2 weeks I got the Fluval filter working this afternoon. The water was a little smelly so I dumped it and filled it up with aquarium water. But after I turned it on it spewed a bunch of junk/poo/dirt from the filter into the aquarium. The aquarium is now all cloudy.

I am wondering, should I have done a more thorough job cleaning the canister since the water was a few weeks old and smelly? Are the fish in danger? Anything I should do to make sure I didn't just royally screw up? This is my first large tank - 34 gallons.

Any advice would be GREATLY appreciated!


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## Deeda (Oct 12, 2012)

Hi and Welcome to C-F!!

Yes you should have cleaned the filter media, canister and hoses prior to installing it on a tank that already has fish in it. A canister filter that is dirty or has been used on someone else's tank that you don't know should be cleaned before using on your tank.

At this point I don't think there is anything you can do except to monitor the ammonia, nitrite and nitrate and watch your fish for unusual behaviors or signs of illness.


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## razak101 (Apr 3, 2021)

Hi Deeda, thanks for replying!

The fish tank, fish and filter all came together. So the water in the filter and media was the original one to the tank and fish. The only thing that changed was that the filter sat unused for about 2 weeks and was sealed while it sat.

I turned it off for now so that it's not continuing to flow. Only the first filter is running for now to see how everyone adapts. Would it be smart to do a water change? I did a partial one today before I messed around with the filter.


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## Deeda (Oct 12, 2012)

A water change won't hurt anything but I don't think it is necessary. I would still rinse out all the filter media though and give it the sniff test, if it smells fishy you should be fine but if it smells nasty I would consider a more thorough cleaning.

Is this your 1st tank or do you have prior experience?


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## razak101 (Apr 3, 2021)

Sounds good. I'll do that before turning it back on.

Not my first tank, but my first one over 10G and with canister filters.


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## Deeda (Oct 12, 2012)

OK!

My personal choice for cleaning aquarium equipment that I buy used is to use regular plain unscented bleach (never use splash less bleach!) and mix up a bleach/water solution based on the bleach concentration listed on the bottle as follows: if the bleach concentration is 8.25%, use 3 Tablespoons per 10 gallons of water and if the bleach concentration is 5.25%, use 5 tablespoons per 10 gallons of water. 
1) First, remove any dirt and debris from the filter media, rinse thoroughly with tap water.
2) Make up the bleach/water solution in a clean bucket or pail. I use my fish only buckets for this procedure.
3) Place the filter media in the bleach/water solution for 10 minutes making sure items are submerged.
4) Discard the bleach/water solution.
5) Rinse the filter media in tap water in the same bucket, filling it and dumping it a couple times.
6) Add enough tap water to the bucket to cover the filter media and add your dechlorinator product as per instructions. You can even double or triple dose without problems. Let soak for at least 10 minutes.
7) Remove the filter media from the bucket and give it the sniff test. If you can still smell bleach, repeat step #6.

I've used this method to clean aquariums, filters, filter media, decorations, filter hoses, etc. with no problems. I usually air dry the cleaned items if I will not be using them right away but if I will be using them immediately, I just make sure I can no longer smell bleach by using the sniff test. Do be aware that plastic or silk aquarium plants will lighten up or degrade using bleach.

Does anyone else recommend cleaning aquarium equipment differently or see something wrong with my method?


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## Auballagh (Jan 29, 2003)

That cleaning plan looks good and very thorough to me.


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## nodima (Oct 3, 2002)

Pretty much how I prefer to approach cleaning of aquarium related stuff. I generally just omit the air dry part at end, but don't see where it would hurt.


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