Hello! Ganesha gains experience little differently compared to other towers. Ganesha has 1-1 attack. This means that it does not attack. Due to Ganeshas ability, that makes it level up when other tower in range of 3 levels up, it won't gather any experience (except those from keys of wisdom)after hitting level 99. Thanks for asking!
After my ganesha reached lv 99, i replace him with dark forge. He gaves me good stuff in early game. :)