Isn't a red texas a hybrid? How can it be an f1?
Default
F1 stands for Filial 1 (or first filial). Filial is a word used to describe sons and daughters, and the first generation from a genetic cross between parents. It's normally used to describe fish that are first generation from wild parents (ie. the fry have come from wild caught fish), so it's seen as an indication of genetic quality.
There's also something called an F1 hybrid, which is the direct offspring from a genetic cross between parents, say a cross between a Goldfish and a Crucian carp. Flowerhorn cichlids, and those mixed Malawi cichluds might not only be F1 hybrids, but could be from lower generations, so they could have genes from several different species.