Tropical Fish shouldn't despawn if placed from a bucket

I think tropical fish, when placed from a bucket of water, shouldn't be able to despawn. I've been trying to build a pond and aquarium with tropical fish in it but, to my disappointment, after some time, they have disappeared. I put quite some effort into collecting these colourful fishes only for them to vanish without a trace for no good reason. Having to use a nametag seems expensive especially when it comes to little fishes whom you'll almost never be close enough to interact with, let alone see the names of. So I suggest that it be added that tropical fishes, and cod and salmon for that matter, do not despawn when placed from a bucket. Thank you for your consideration.