Your stock is alive

Fish arrive as cheap fry. What happens next is on you. Feed them, keep the water clean, treat them when they get sick, and they grow into adults worth double — and start breeding stock you never paid for. Neglect a tank and you watch your inventory get sick, stop growing and stop selling.

Water chemistry that actually matters

Every tank tracks temperature, oxygen, pH, salinity and dirt. Heaters hold the temperature. Filters and live plants carry the oxygen. Driftwood pushes pH down, coral gravel pushes it back up, and reagent bottles fix it fast when you have no time. Dirt climbs on its own — faster with more fish in less water — and eventually you grab the tools and scrub. Some species also refuse to share a tank, so read the labels before you drop two predators in the same glass.

Breed for grades you cannot buy

Suppliers only ship bronze-grade fish. Silver, gold and diamond come from your own tanks — offspring grade rises the better you care for the parents. Diamond fish are rare, gorgeous, and never guaranteed. Put them on display instead of selling them and they pull more customers through the door.

You set the prices

Buy low from the supplier catalogue, then price every item yourself. Customers know the market rate and have a limit above it — push past that ceiling and they put the fish back on the shelf, pull a face and leave. The exact limit is never shown, only a range, so finding the edge is your job. Better merchandising and a more popular shop raise the ceiling for everything you sell.

Build the shop you want

Start with an empty room. Place shelves, tanks, filters and lighting from blueprints, rotate and rearrange until the layout flows, repaint the floors and walls, and buy the extension when the register can cover it. Name the shop and mount the sign above the door in whatever colour you like.

Decorate every tank by hand

Inside each aquarium you place substrate, plants, rocks, driftwood, coral, wrecks and figurines — moved, rotated and scaled freely like a 3D editor, right down to the sticker on the glass. Pick one tank as your Main Aquarium: it is never for sale, it is your showpiece, and the better it looks the more customers walk in.

Run it together

Invite friends into your store and split the shift. One works the supplier terminal and re-prices the shelves while another feeds the tanks, cleans the glass and talks a browsing customer into something bigger. Everything stays in sync — the shop keeps trading whether you are behind the counter or elbow-deep in a filter.

Five stars to earn

Sales, variety, breeding and lifetime revenue push your shop from zero to five stars. Each star unlocks rarer species, more customers and more room to grow. And when the day ends, step outside — there is a cat, a merchant selling things nobody asked for, and something wandering the street at night.