The menu button is located towards the top right of the playing area, from there you can access the following features in the game:
Next Goal:
This tells you the next thing you should aim to complete in the game, for example, complete the league you are currently in.
Decorate
Here you can add in any items that you have purchased for your pond, or alter their location. If you have any themes unlocked you can also click the 'Themes' link to change the overall theme of your Magikarp pond.
Items
The Items page allows you to use the items that you have purchased, such as Training Soda.
Achievements
As you progress through the game you complete achievements, don't forget to check this page in the game often as there may uncollected awards such as Free Diamonds or free coins waiting for you for completing achievements.
Purchase
Here is you spend real money for Diamonds and exchange tickets. If you don't plan to spend any cash in this game, don't go to this page!
From the purchase page you can also go to the Exchange Office where you can trade in exchange tickets for items or coins.
Settings
the Settings menu is also found via the menu link, here you can change the game settings and read up about the game.
Diamond Miner
This is a speciality item which is only available after you have PURCHASED at least 2500 diamonds! With the purchase of diamonds you get exchange tickets also when you have 2500 you can go to the Exchange Office and proceed to exchange 500 tickets for each of the items in the exchange office, Once you have made 5 exchanges the Diamond Miner will be available.
The Diamond Miner grants you 100 Free Diamonds every day!