While I do not have a Reef Angel it would help if you can thoroughly explain
Your system (IE: Head unit , Modules X, Y, Z, etc, Firmware version, etc)
The issue (IE; Froze up)
What steps you have taken (IE; Rebooted, Attempted Firmware reload, etc)
Hey, unplug it from the system. Unscrew the 4 black screws and remove the back plate. Remove the battery that holds the real time clock. This will clear all from memory.
*Leave unplugged for a good 30 min. You might need to plug in your pump directly into an outlet while you do this.
Once completed: Put it all back together and do an initial setup. Once done there, reload you source code and problem should be solved.
If not, more details as indicated above (primarily version) would be greatly informative.