thanks so much guys!! Jammers...I didnt have luck cutting the new piece. I tried cutting it with a jigsaw...but the acrylic just shattered =(. So i just pulled the original piece as high as it would go and build up the gravel on the bottom to fill in the gap. I used a drill bit that was smaller than the size of the betta but big enough that i didnt feel to put too many holes. However I will be agging more holes to allow for better water circulation. Good luck with cutting the acrylic...it was pretty tricky....let me know if u need tips.
And Betta Fish Bob...thanks so much! Dad is a hobby photographer...so it kind of rubbed off =)