fish struggling after new filter installation

[cowboy]

Hi,
I'm new here, so hopefully I've posted this in the right spot. I've had a betta for a few months now, and everything's been fine, but after replacing the filter cartridge this morning - I've got a tetra whisper internal cartridge filter - he's been acting really strange. He just goes to the top of the tank and stays there, not moving, which isn't like him at all. I'd really appreciate any advice on what I should do about it.

Thanks for any help

[kingrise]

Can you post a picture of the filter? What's the specific type of betta you have?

[FinFan]

It's possible that the cartridge change caused a decline in good bacteria in your tank. This could be the reason your betta's behavior has changed.
To check the water parameters, do you have a test kit available? If not, consider taking a water sample to your nearest pet store for testing. They should be able to provide you with the necessary information.
If the parameters are off, I would recommend doing a partial water change. However, avoid vacuuming the gravel as this can further reduce the bacteria in your tank.
A good practice when changing cartridges is to place the old one behind the new one for a few days. This allows the new cartridge to develop the necessary bacteria, minimizing potential issues.

[finnisher]

This thread is redundant, already discussed elsewhere.

[SeaBidder]

It's possible that the cartridge change caused a decline in good bacteria in your tank. This could be the reason your betta's behavior has changed.
To check the water parameters, do you have a test kit available? If not, consider taking a water sample to your nearest pet store for testing. They should be able to provide you with the necessary information.
If the parameters are off, I would recommend doing a partial water change. However, avoid vacuuming the gravel as this can further reduce the bacteria in your tank.
A good practice when changing cartridges is to place the old one behind the new one for a few days. This allows the new cartridge to develop the necessary bacteria, minimizing potential issues.

I'm glad FinFan provided such helpful advice - it's really reassuring to see people looking out for each other on this forum. I especially appreciate the tip about leaving the old cartridge behind the new one for a few days, it makes total sense to allow the bacteria to grow and prevent any issues. Has anyone else had a similar experience with their betta after changing the filter cartridge?

[finnisher]

I agree with FinFan's post, very informative advice. Good job.