Fish trapped in Biocube filter chambers
I just bought an Oceanic BioCube 8g. I put 5 young, 4-month-old microctenopoma in last night and this morning only 3 greeted me. One was trapped in the 1st filter chamber. I thought he may have gotten sucked in through the intake slats, but he's too big. Then I found the last fish in the third filter chamber. He is much, much too big to have gotten sucked in through the slats. So I'm guessing they both jumped over the barrier into their respective chambers. My smallest net isn't small enough to fit into either chamber, so I've shut off the filter and filled the tank as full as I could to allow the fish to hopefully jump back over the barrier into the main tank. (Hopefully they won't convince their siblings to move into the filter with them.)
1. If this plan doesn't work, any other ideas about how I could get them out?
2. How do I prevent this from happening in the future? I'm thinking of maybe just modifying a fluval sponge to sit above the filter chambers so that everyone will just bounce off of it if they try to go over.