From time to time in the late 1990s I would take the 20 mile drive across Toronto, to visit my good friend Jim Robinson. Jim had more tanks than I had ever seen in anybody's basement, literally hundreds of them, big and small and was a founder of the Canadian Killifish Association in the late 20th ans early 21st centuries which should give you a good idea of where his interests in fish were focused. I would spend hours there talking with him and peering through his tanks to see what was new - and there was always something new, fish came and went through Jim's basement like some sort of aquatic way station.
On average I'd go there about once every six months or so, and somewhere in the mid 1990s I was looking in a rack of small killi breeding tanks and found an empty one. "Jim this tank is empty" I said staring at water, a sponge filter and nothing more. "What does the tag say?" Jim replied. "Rivulus punctatus" I said. "Crap, they must have jumped out" he said in a somewhat disappointed tone.
Killifish jump, and of all the killies, Rivulus are the worst for this; It's what they do and people I know that have collected them in the wild have told me they've found them in so little water - literally hoofprint puddles in the soft South American jungle mud. They will jump out and flop around in the moist night air looking for food in the next puddle. So it's no great surprise Rivulus jump or that they're well adapted to this. Frans Vermeulen, Ron Harlan and Roger Brosseau have seen and reported this (pers comms), and many others no doubt, but I've only heard it first hand from Roger, Frans and Ron.
Back in Jim's basement fishroom I kept looking at this rack of tanks and came to the end of the rack and turned around to look at the rack of tanks behind me when something caught my eye - movement from down below. Now, Jim uses a continuous flow recirculation system and um, well, err, it leaks a bit. There was a puddle of water pooled up in that particular corner of his basement, a triangle of water about a foot and a half square and roughly a quarter inch or 5mm deep. But something just moved.
I found a fish. No, I found two fish. "Uh, Jim, there's fish on your floor". "Oh, what do they look like". "Rivulus". "Figgers. Ok, just leave them there". Ooooook dude, they're your fish.
Six months later I'm back looking around again. Just for a joke I go look at the puddle. I do not see the two small fish. No, I see two almost three inch long fish and maybe 40 fry. The water barely covered half the height of the adults body.
"Uh, Jim there's a bunch of fish down here". "Yeah I know. They do better there than in my tanks".
Rivulus punctatus "Jim's basement floor" became common in killifish circles in that time period in the Toronto area and for about another 18 months I'd periodically see them when I went to visit. The conditions were just right... a constant drip drip drip from tanks overheard loaded with baby brine shrimp; the odd fly would land seeking moisture and get a big surprise; a bit of algae grew there and of course the commensurate infusorians. It was about as natural an environment as you could provide these fish as it very closely duplicated their existence in the wild.
What happened to these fish? Jim moved. And now he has a dry basement.