Thats an interesting question, Patrick.
Again, lets agree, that we are not discussing if one way is more correct than the other, – but its interesting to learn about the behaviour of paros.
Most fish as I see it are territorial mainly within their own species, – that is actually also true of parosphromenus.
My only ‘mixed’ aquarium with paros is a 60 liter with boraras, 8 paro males and 1 betta albimarginata, – 🙂
What I can see, which was a surprise to me, is that these Paros are quite a bit more active and lively than the ones I keep in small breeding tanks. They go eagerly around in the whole tank, they are first on the food, just like any other fishes. They compete with each other for food and are not hiding at all. They will establish a certain hieraki within their own flock, so there are males that are more dominant than others.
The ‘tricky’ part for me with a big tank like this, is that I provide a lot of plants and hiding spots for the paros, and I think thats important for them to regulate also their own agression towards each other, – but this also means that I have very little posibility to actually follow if everything is fine or not, – I can loose track of them in such a big tank.
But this of course is not the setup you are asking about. I would hesitate to have more agressive species with the paroes, – they might be able to adapt in some way, but not actually become a dominant fish then, – I would think they would have to accept the role of being subdominant to the more agressive species ?