Thusly " Spake
Unto All:

Leopards (brachydanio frankei) and Zebras (brachydanio rerio) are two
different species, so they will not breed.

AFA is known that is not true. The leopard has never, despite
considerable effort, been found in nature, and is now believed to be a
captive-bred strain of zebra danio, and /Danio frankei/ is today
considered a synonym of /Danio rerio/, with which it will also
interbreed. However, the leopard danio has reduced fertility, which
*might* indicate that it itself is a hybrid between /D. rerio/ and
some other species of /Danio/.

The genus /Brachydanio/ is today considered a synonym of /Danio/,
comprising most of the small species of danios, whereas the genus
/Devario/ comprises most of the big species (e.g. /Devario
aequipinnatus/, the common giant danio).

Also, FWIW, I do not recall ever having seen a silver or blue strain
of leopard danio or zebra danio. I have seen albinos & partial
albinos, though.