Ok thank you so much for that advice, My background and the sides fit tight there is no way a blade of grass could get behind it let alone a betta. The bottom is under the gravel level the top is level with the tank.Alasse said:I'm sure water gets between them, hasnt caused any issues though so far.
I silicone it the best i can, mainly to prevent fish from getting behind rather than water
Once again thanks for the help and sorry for kind of hijacking your thread, Your advice will also come in handy to others who want a 3d background.