The Neptune Fish requires a special combination to breed this fish in Fish with Attitude. As you may have notice a deep message was left in the description to you players of Fish with Attitude.
Fish with Attitude: Neptune Fish Breeding Guide
To breed the Neptune Fish you need to use the Diamond Fish and an Devil Fish for a chance to get the Neptune Fish in your Fish with Attitude game
Fish with Attitude: Neptune Fish Evolution Guide
Most fish in Fish with Attitude goes through a process where you must feed them once they have hatched from the egg. Once you feed them for the first time, they will begin growing and once they finish they will become an adult.
Fish with Attitude: Neptune Fish Earnings
The fish has a max earnings of three stages and you can train them three times. Each time will increase their earnings allowing you to earn more for your tank. All of these costs are different for different fishes.
Fish with Attitude: Neptune Fish Evolution