Is this an egg spot ?
If not, what fry could i expect if i breed him (black crowntail) to a female( red cambodian double tail) ?
5 to 10 years
Some males have false egg spots, bit they mostly appear when the fosh has just eaten/been over fed.
You won’t get any double tails and depending on the fin type (other than double tail) of the female you will likely get half suns/comb tails. Color is harder to guess at.
I would’t bother spawning them unless you’ve got a few spare tank laying around and a bunch of jars/cups for when they start maturing. Plus the fry will not eating anythong but live foods so if you don't at least have a micro worm culture or brine shrimp hachery the fry will starve. Been there, done that. Thankfully my spawn was a mere 20 (usually closer to 200) in number and I’ve been able to house the juveniles in my sorority.