As I mentioned on a different forum
I don't conduct experiments with Dario tigris. They just happen to sit on top of the food chain in most of my tanks. I keep a minimal amount of fish (mostly Dario) per tank in order to preserve populations of crustaceans and nematodes in the same tank.
I believe the observation given by Louis could very well be applicable to Dario tigris.
I once had a scape (in a 1 meter tank) that had a very clear boundary in the middle, along with two males and one female. The males each owned one of the sides of the tank, perhaps due to the clear boundary in the middle, and disputes were very, very frequent. Spawning took place in this setup. But I hated staring at the tank because of the disputes.
So I changed the scape to an island, see picture below, and added a third male (yes, for comparison, I should not have done that). The four oftentimes group together; see picture below. I never notice any disputes ...and thus far, never noticed any breeding either.
The other remark by Louis regarding Dario dario is one that I have read before about this fish; they aggregate in groups in the wild. Perhaps the same is true for tigris. Aggregate under conditions a,b,c, settle territories under conditions, x,b,z, etc. If I'd live a thousand years, I would probably have visited Myanmar by now and observe tigris in the wild.
Most of my tanks only have a solitary male. I seriously wonder if this is the right thing to do from the fish's perspective.
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View attachment 199583
For breeding, I currently keep 1 male and 1 female in a 60cm tank.
Louis talked about a visible spot on the female. I notice the same thing on the dorsal side. Look at the white mark. It is not something permanent.
View attachment 199585