Fishdom 3: Special Edition

To unlock this achievement, you'll need to buy enough decorations for your aquariums to get 5 of them to the largest trophy size. This will take a long time and a lot of money to do, so you should start working on this from the moment you start the game, and don't stop until you finish the fifth aquarium. You'll unlock the ability to purchase your fifth aquarium somewhere around level 25 or so, but reaching the biggest trophy will take a ton of decorations. Each successive aquarium takes more decorations to upgrade to the next level. You essentially should be spending all of the money you earn from levels on decorations. Continually upgrade your first aquarium until you get the biggest trophy, and buy decorations as soon as you can afford them. Buying them levels you up, which means more money, which means buying more decorations. Once you fully upgrade your first aquarium, save up money to buy a second aquarium. Now repeat the process, but this time it'll take longer - more accessories - to fully upgrade this aquarium. Continue with this pattern until you have five fully upgraded aquariums.

This will take a ton of time and money. Expect to be close to level 40 by the time you finally finish this. Don't waste money on fish or anything else until you have this achievement done, since it'll take the majority of your time and money to complete this.