Of course, Fishdom 3 is only a let-down if you're familiar with the series. If you haven't yet played a Fishdom game, Fishdom 3 is a great place to start. The over-reaching idea is to populate and decorate your own fancy fish tanks, and that's done by earning money playing match-three levels. Match-three sharks will get the mechanics within seconds, but for you match-three minnows, the game goes like this: on a field full of fishy icons (shrimp, starfish, manta rays, etc), you click to swap icons and create rows of three or more. These then vanish, causing the icons above them to cascade down, often creating additional matches.
Certain types of matches make power-ups appear such as dynamite, firecrackers and depth charges, and these explode when matched or clicked, blowing everything around them to smithereens. Completing a match-three level entails clearing the playing field of gold squares by matching the icons on top of them. Once you've cleared them all, you're awarded a chunk of money to spend in the Store.
The Store is important, because although completing match-three levels is fun, it's only half the game. The other half is customizing your own fish tanks. With the money you earn playing match-three, you can shop in the Store for fish, decorations, plants and backgrounds. Different tanks hold different numbers of fish, and tanks can earn up to three awards depending on how well they're decorated. Every time you add a fish or a decoration, you earn experience points. Experience points are important too because they enable you to level up and unlock better and better fish, plants and decorations. You also earn experience points by keeping your fish happy, which means feeding them regularly and cleaning the algae off their tanks.