if you do have to take the frnt pane back off. you might try using less silicone. i know when re siliconed my daughter's terrarium the more i used, the more bubbles i got
so after my 3rd attempt its got some pretty nice seems now
oh yeah, and it looks like the two hole shsould handle the water flow quiet nicely
on a side note, the water looks so nice in that glass!!!!!!!!
Thing is when I first put the glass on, no bubbles in the seams!! So honestly no idea :-/