How do u defend Ballonian

I have no idea how to defend it

i have centralized air lev 6 and wizard towers also my air bombs are place thoughtfully

If you are a town hall 8 trying to defend against level 6 balloons, its not going to happen.
If you are a town hall 8 facing level 5 balloons, you are doing the best you can.

This is pretty much like asking for a th8 anti-hog base... TH8 isn't ready to have a chance against successfully defending against max balloons or hogs unless you get lucky with a sloppy attack

A dragon in clan castle might help. Or perhaps swarms of minions. Other than that, not much you can do.