Games like Nanoquarium
Games like Nanoquarium include Chillquarium, Spirit City: Lofi Sessions, Slime Rancher 2, Tiny Pasture, and Cast n Chill. We matched them by the tags players give Nanoquarium on Steam (Simulation, Cozy, Relaxing, Casual, and Creature Collector): closest matches first, and among equally close ones the better-known games.

Chillquarium
Shared: Creature Collector · Idler · Cozy

Spirit City: Lofi Sessions
Shared: Cozy · Relaxing · Creature Collector

Slime Rancher 2
Shared: Relaxing · Cute · Simulation

Tiny Pasture
Shared: Idler · Casual · Cute

Cast n Chill
Shared: Relaxing · Cozy · Idler

Sticky Business
Shared: Simulation · Relaxing · Casual

Kabuto Park
Shared: Cozy · Casual · Creature Collector

Luma Island
Shared: Cozy · Simulation · Casual

Placid Plastic Duck Simulator
Shared: Relaxing · Casual · Cute

Is This Seat Taken?
Shared: Relaxing · Casual · Cozy

Stardew Valley
Shared: Simulation · Relaxing · Farming Sim

Tiny Glade
Shared: Relaxing · Cozy · Casual

Minami Lane
Shared: Casual · Relaxing · Simulation

Tiny Bookshop
Shared: Cozy · Relaxing · Simulation

Leafy Corner
Shared: Cozy · Simulation · Casual

MyVoiceZoo
Shared: Simulation · Casual · Creature Collector

Hello Kitty Island Adventure
Shared: Cozy · Simulation · Casual

Joyquarium
Shared: Simulation · Creature Collector · Relaxing

Spilled!
Shared: Relaxing · Casual · Cozy

Creature Kitchen
Shared: Cozy · Creature Collector · Relaxing

Garden Life: A Cozy Simulator
Shared: Simulation · Relaxing · Cozy

Rusty's Retirement
Shared: Simulation · Idler · Relaxing

Unpacking
Shared: Relaxing · Casual · Cute

Cozy Grove
Shared: Relaxing · Cozy · Cute