Go into settings > applications, tap on an app and see if it gives you the option to MOVE TO SD CARD. Alternatively install an app (you may need to delete one if you dont have any space) called Apps2SD - this gives you the ability to move certain apps to the SD card. Also have a look to see where your camera is saving new photos and if required change the storage setting to SD.
As you probably know the Ace has a very low amount of internal memory which can be filled very quickly.
I work for O2 but my comments and opinions posted here are solely my own and do not reflect those of Telefonica.
