How do you get 1000 coins in happy aquarium?

you get get more coins by doing
1- login to happy aquarium everyday and click on your chest and your neighbor chest, try add more neighbor as much as you can the more neighbor you had the more coins you will received daily.
2. get your fish up to adult, then sell it for some profit. you may check the profit list here
http://www.yayeasy.com/happy_aquarium/happy-aquarium-fish-details-and-profit/
they are also updates a lot of info regarding happy aquarium. hope it can help you