cross breeding?

[mizu-chan]

I have Mollies and Sword tails in the same tank. I've some problems with one of the females when she gives birth. They all come out still born. :/
Do you think it could be because of cross breeding?

TIA. (:

[islander]

Re: cross breeding?

Howdy

I would say that it would be impossible for a molly to cross with a swordtail because they are not in the same genus.  But mollies, guppies & endlers are in the same genus and it is rare for a molly to cross with a guppy and they are usually sterile but common for a guppy & endler to cross and they are fertile

Swordtail & platty are in the same genus and when encourged they will cross; some times the hybrid vigor works in your favor and you get cool fish that are fertile, other times they are sterile or there is fertility problems.  It usually depends on what species are crossed.

One possibility of why the mollies or swordtails are producing still born fry is that one or both parents carry a lethal gene that causes this.  Or there might be environmental factors that would cause this.  later, ken