I had difficulty searching for specific ideas for preventing my bubble eye from becoming stuck to the Rio-brand internal filter I have (aka jet filter?). Koko also has the following recommendation btw: http://www.kokosgoldfish.com/forum/index.php?showtopic=17635
My other idea is to have large enough holes covering the filter intake (many thanks to my husband who helped me with this idea
1. A plastic grating easily available from the lsf (cut to size later)

2. Some plastic cable strings

Note how item 1 folds into a curve? I decided to use this original semi-cylinder shape to cover around the filter, leaving about 1cm space around the intake area. After cutting to shape with a plier, I tied several item 2s (3 in my case) on the opposite ends to keep the semi-cilinder shape intact.
I also cut a hole at the front to allow the filter output to protrude (this also keeps the grating in place).
Since the edges can be quite sharp, I put the formation at the corner of the tank, and secured it into place with some rocks+gravel at the ground. It stands on its own anyway (you can easily improve this by adding suction caps somewhere perhaps).

See how she's trying to get injured again - no more burst bubbles this time, Patchie