AquariumCraft

AquariumCraft lets you build and customize your own aquariums in Minecraft. Place down an aquarium glass block, fill it with water, and start adding fish using
   buckets — cod, salmon, tropical fish, or pufferfish all work.                                                                                                 
                                                                                                                                                                 
  Each aquarium has a 4x4 floor grid where you can place sand, gravel, red sand, soul sand, or magma blocks. Soul sand and magma create bubble effects inside the
   tank. You can also drop in decorations like coral, sea pickles, seagrass, and kelp to make things look nice.

  Fish actually swim around with animations, and they need to be fed. Toss some Fish Flakes into the food slot (you can craft them or buy them from fisherman
  villagers) and your fish will stay happy. Leave them without food for too long and they'll get sluggish, lose color, and eventually die — dropping bone meal
  instead.

  You can place aquariums next to each other and they'll connect into one big tank. The glass borders between them disappear and fish swim freely across all
  connected blocks. If you don't want them to connect, just shift-click when placing.

Works on both Fabric and NeoForge for Minecraft 1.21.1.