yeh, just wonderingWhy should it mess up their genes?
You don't normally keep them together because most killifish come from soft acid water and guppies come from hard water with a pH above 7.0\
i was saying least killifishIf you are worried about them interbreeding, they can't as they are totally different species.
i have a 283g...Mine were ok with guppies, WCMM and Medaka. Only problem being their size in a largish tank 120L made em difficult to see. You’d sometimes have to sit for ten mins before catching sight of one. They’d occasionally swim through the bigger fish but most times kept towards the bottom and back amongst the plants.
I moved em into a 39L and they’re visible almost immediately.