Hello all! I really enjoy keeping pet fish in my minecraft survival world, however recently I have noticed some go missing. More specifically, I have had a few pufferfish on my current survival realm in a pond and they have all went missing within a couple days. I believe I saw one of them die from suffocating, but I'm not totally sure how they keep dying. Any tips on how to keep them alive and why they are dying? Thanks!
P.S. I know that nobody on my realm has been killing them, and there is no way for mobs or anything that might kill them to get near my pond.
EDIT: Yes all of these fish have been from buckets or named
I presume you have placed the fish with buckets? Otherwise they can despawn.
I don't have much personal experience with keeping fish but based on what I know about how to stop animals from suffocating in walls I would suggest surrounding them with waterlogged fences to keep them within the volume of water.
(Including on the bottom.)
Though fences don't look very nice, blue glass panes might be slightly less noticeable.