A few days later another loach disappeared, no body. Just 1 pictus cat fatter than the rest...

Yeah, I get that they could get out, but I think a lot of you are overestimating the size of that hole. It's 2" wide, and directly under it is a tangle of branches. Hardly "gaping" imo but I am aware there's a risk.
View attachment 1511343
Again, I know they could get out if they really tried. Like I said it's the obvious answer. I just thought it unlikely that 3 would disappear in that way in a short window of time when they have been fine like this for months. In the past when I've had jumpers they almost always leave a mess on top of the tank....I have nothing but dust that I can draw in with my finger...
Stupid question maybe… how bout those overflow boxes? Looks fairly easy for someone to go right in there with the water level. I keep plastic mesh type lids on the one i do have. B hard to see a bala in one on the black.