Fluval 205 filter leaking!

I did a filter clean, set up as usual only to come home after popping out to find it leaking! Took it all apart and reset it back up only to find it started leaking again.
I have googled and am now wondering am I missing a seal completely? I have never had one and haven’t had any issues. I have had it for over 4 years. I bought it second hand and it has worked no issues in that time.
I have added photos so you can see if it is missing a seal. Thanks in advance.
Also, how long can my fish survive without a filter? Shops not open here for another 17 hours!

There should be a rubber o-ring that sits between the motor and the case. It's actually a square shape but it' still an o-ring.

A worn/ stretched o-ring won't seat properly and will leak.

Smeer some Vaseline on the o-ring to help it seat better.

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Fish can go for a few days with filtration, however you should stop feeding them during that time.

If the filter is only leaking a bit, put it in a big bucket, esky, storage container and let the water drip into the container while the filter runs. This way the tank will still be filtered and the excess water will collect in the bucket. You can scoop out the excess water and tip it on the garden and top up the tank with dechlorinated water.

If the filter is leaking a lot, clean the media/ materials and put them in the tank. Wash the filter case and motor and put them to the side. Leave the media in the tank until you get the filter fixed.

I had a leak once and it was the internals not fitted properly so not allowing the lid to seal. Funny it was after cleaning and it's been ok before. I'd remove n refit the filter bits and unless you lost a seal it will be ok.