Since you didn't state what device you are playing the game on, I'm going to assume that you are playing on an Android phone. The below will assist you:
Many crashes occur because of low memory conditions on a device, rather than a problem with our game. When too much memory is taken up by running applications, the operating system will terminate the currently running app. When that happens, it will look exactly like a game crash, since there is no message from the operating system to tell you what happened.
In order to minimize this type of crash, make sure that you close any apps that you aren't actually using before playing Fish Tycoon. Merely tapping the home function will not close an app, since Android OS is a multi-tasking operating system and the apps will continue to run in the background. Use the application management function in your device's Settings panel to close any apps you don't need running. This will make more memory available to run Fish Tycoon.
For more information on this, please see the below, while keeping in mind that application memory is not the same as device memory:
Current smartphone operating systems are multitasking operating systems that are capable of running many tasks at once. When using a device that supports multitasking, such as most current smartphones and tablets, using the Home function does not close the app that was running at the time. Instead, the app is put into the background, where it often continues to run some of its processes. These processes vary from app to app, as does the amount of memory required to run them. The operating system manages all of the running tasks, but it doesn't always leave enough free memory to launch additional applications or processes, since most mobile devices have significantly less application memory than a typical laptop or desktop computer.
This situation will, unfortunately, require the user to manually clean up memory. The easiest method is to completely power off the device and power it back on, but applications can be individually closed to free up memory. There are a number of ways to determine what apps are running in the background and individually close them. Those methods vary, depending upon the operating system that your device is running.
There are many useful references for managing applications on various Android devices, including the owner's manual or user's guide that came with the phone or tablet. You can also use procedures that can be found on the Web, such as
this one at eHow, to help you close applications and free up memory. Keep in mind that various manufacturers and carriers often customize the Android OS, and the procedures for your device may vary from what's described on the Web.
Please note that older devices with minimum memory may require more frequent closing of other apps.