My RSPCA experience:
STBXH had an enormous tank full of tropical fish. He & 9yo dd1 spent hours every week testing the water quality, tweaking the ph levels & generally faffing with it - it was a sweet, geeky dad & daughter thing they did together. I've always rather disliked the fish tbh - smelly & dull.
I kicked H out (for impeccable 'Leave the bastard!' reasons).
Among other stuff, I made it clear that he had to shift the bloody fish. 3 months later, I'm doing my inadequate best to feed & clean out the damn fish each week, & dd1 is getting increasingly distressed that they are not being cared for properly. Given size of tank, this entails being armpit deep in smelly water on a weekly basis & lugging half a dozen buckets of foul water out & fresh water in.
STBXH continues to fob me off about moving the buggers. I ring RSPCA to explain fish have been abandoned.
RSPCA ring STBXH. He tells them he left the fish in my care & doesn't see why I can't continue to look after them for him indefinitely.
RSPCA ring me back & explain that they can't do anything, unless I neglect the fish or abandon them by moving out of the property without making provision for them, in which case they'll prosecute me. Oh & can they have a fiver please, or better yet a regular direct debit?
STBXH rings me to gloat that RSPCA say I'm stuck with fish.
I tell him actually I've found a small charity which is coming round to collect entire fishtank & set the tank up in an old people's home.
STBXH appears two hours later & collects fish.
RSPCA are off my donation list.