The Fancy Treats are a type of food you can feed your fish in the Aqua Pets game. When fish in the players tank start to flash, this means that you have fed the pets the correct fish food and can collect rewards from them. Rewards include, coins and even sometimes a pearl, although it might take up to 8 days for pearls to appear after feeding them. You can feed all fish these pellets.
"Fish that eat Fancy Treats tend to be more happy than those who've eaten Basic Food Pellets."