damian :pixelcatsuper: (not the omen) :blobross: on Nostr: nprofile1q…5zkp9 there are a few options I think - if it is the original cartridge ...

nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpqh5fzur5m38hk0z9839ppf68app8ec5ej5dvdukcg7k3e8vwjvfasn5zkp9 (nprofile…zkp9) there are a few options I think - if it is the original cartridge (just the plastic tube) you kind of have to remove it, I don’t think any other way is possible. You can use an eye dropper or little syringe or something like that which makes it a bit easier to fill the cartridge.
The other way is to use what is called a converter - they look like the plastic tube, but have a screw type mechanism most commonly on the end with a plunger. (There are other types, but this is a common one) when you use these, you can still use the previous method, but you can now also leave it attached to the pen, and dunk the writing nib end into the bottle with the screw plunger thing extended all the way to the end of the converter tube and then twist it back up to basically drink in/vacuum up the ink to the cartridge. I usually have to go up and down a few times with the plunger to get it to fill, but this works fairly well (minus getting the nib end of your pen a bit inky, but that is easy clean up.

I’m not sure which type you are using, but hope that helps a bit. I can send some photos too if that helps.