Hello. I am currently cycling a 240l tank with 8 neon tetras (this tank + filter: ) Just now, my sister told me a fish was being sucked in by the filter and couldn't move. So I closed the filter and the fish swam away. I feel uncomfortable with filter because before, it sucked in one of my 9 neon tetras and killed it and I don't want it to happen again. What can I do to block up this type of filter? (I think its holes are big enough to suck the fish into it) Please help ASAP. Thank you.