#casperrrae

I read this fic a while back on AO3, and I was wondering if y'all could help me find it. Harry and Ron went to a circus, and Draco was a merman being kept there. But his tank was dirty and he was underfed, so Harry decides to take him back to his house, and nurse him back to health. He keeps Draco in the bathtub, but after Draco starts to get sick realizes he needs to be put in saltwater. At some point in the story Draco's owner comes back to get Draco, but Harry doesn't let him leave. Harry can't swim in the fic, so Draco teaches him after Harry builds him a huge tank thing in a spare bedroom. It was part of a series with four parts. Thank you in advance!