Breeding

• Breed fishes of the same species type. Mating fishes of the same species will give their offspring a longer lifespan and greater success at surviving childhood. It is also possible to group a pregnant fish with normal fish and get them pregnant for breeding.
  
  

Sick Fishes

• Sell your sick fishes right away. Rather than spending money on medicines to cure them, you can use the sale profits to buy new and healthy fishes. Do this by dragging sick fishes into the Sale Tank. Keeping a sick fish too long in your tank will lower its condition and kill off your other fishes quicker than normal, especially those that are 6 years of age or younger.
  
  

Magical Fishes

• Keep your magical fishes alive as long as possible and put a high sale price on them. These fishes are identified by sparkles around their bodies. These are the most sought out fishes by customers and will always sell at the highest price. These can be found by crossbreeding high-end species hatched from the most expensive fish eggs you can buy.
  
  

Tank Population

• Have each tank population to no more than nine fishes. You want to keep a balance of fishes because while each tank can hold 20 total, it will quickly become dirty and make your fishes sick, leading to a shorter lifespan and quicker death.
  
  

Good Sales

• Place ornaments for your sales tank and purchase Advertisement Research in level three. Having these for your sales tank will result in a higher than normal sale price for your regular fishes and even higher prices for your magical fishes.
  
  

Feeding

• Feed your fish at the start of the game, before entering the Store screen, and right before you shut down the game. This will ensure the greatest survivability of your fishes as well as reduce the chances of them becoming sick. The key is to keep your fishes as healthy as possible to fetch the best sale price.