Chillquarium is a calming and enjoyable idle game where all you do is just collect fish, grow them, and sell them for profit in-game so that you can then use the in-game currency to purchase new tanks, lighting, soil, and different species of fish and invertebrates, both freshwater and saltwater.
Each fish or invertebrate, such as snails and shrimps, starts as an offspring. Offsprings are usually worthless, costing only a couple of cents, depending on the species and rarity. So it is up to you for them to reach maturity, become more valuable, and unlock them for your collection. The fish mature by themselves, some longer than others, but feeding them pellets will speed up maturity. Once they become adults, you unlock them in your collection, and you can sell them for a considerable profit, but keeping them in your tank longer will also allow them to become more valuable. So, while you wait for your fish to reach maturity, you can just kick back and marvel at all the beautiful fish.
The gameplay is quite simple, but what is not simple are the game's graphics. The game is pixelated art, meaning the sprites and background designs are drawn in pixels, like in an old video game; however, that is the charm of this game. The background feels soothing to look at. The fish are also neatly designed and colorful.
One complaint is that freshwater and saltwater fish can apparently stay in the same tank, which is unrealistic because these two types of fish can not survive in either water salinity.
In summary, Chillquarium is a game for people who want to avoid the hassle of taking care of a real aquarium. Instead, they want to keep fish virtually while also destressing and watching beautiful fish.