Derek,
You can make screens that slide over the ends of your PVC to keep the fish in or out.
I make several sizes depending on the size of my fish. If you don't have the material (plastic cage material) I'd be happy to send you a few if you tell me what size your PVC and fish are.
![](http://i11.photobucket.com/albums/a169/CecilBaird1/IMG_1369_zpsf9lgvvcg.jpg)