my ex has found the profile and is messaging from new accounts

Trying to keep this brief and factual because I have gone round in circles about it privately.

Ex from a relationship that ended badly last year has found my profile on the app. First contact was a message from an account with no photos, referencing something only he would know. Blocked it. Nine days later, second account, same thing. Blocked. There has now been a third.

None of the messages are threatening in a way I could point at. That is almost the worst part. They are chatty. They are the sort of thing that would look completely fine if I showed it to someone out of context.

I have changed my handle and swapped one of the photos. He found the profile again anyway, which I assume means he is just going through the local feed until I appear.

Practical question: is there anything at the settings level that actually stops this, or am I going to be doing this forever? And has anyone had reporting work for repeat accounts from one person?

Block each one the moment it appears, do not reply to any of them even once, and keep a record with dates and screenshots. The record matters more than it feels like it does right now, because the pattern is the thing that is legible to anybody you might later need to show it to, and no single message ever looks like much on its own.