Hello Martin and welcome to this forum and homepage. I hope you will find much more information here in english which will help you, – that is what we hope to do, to help people as you with an interest in the parosphromenus species. Because it is not so much information that you can find about them.
I am happy to read that you are already making some of your own experiences with the fish, – in the beginning it is difficult, but once you learn by experience and from others it becomes easier. And the fact that you have already had the fish spawn is a very good sign. So keep up the good work 🙂
Your observation about the Copella is certainly helpful, – I think you are right, – if you would like the paros to spawn they should not be kept with other fish. Parosphromenus are not very assertive or fast as f.example Copellas and they will not be able to get to the food quick enough, as well as the fry will be eaten.
P.sumatranus is as far as I know not an easy species to get to spawn, so that is very good, – now the big question is how to do it again 🙂 … now it probably becomes difficult.
Food is a difficult matter often, but artemia is a very good food, and most other kinds of small live food, – I am not sure about glass worms, normally I would think they are in the too big range for the fish, and its not so good to use them as main food, – but small amounts (and small sizes) is good. Dafnia are also good.
The tank can be more or less helpfull as well, – its very good as you do with leaves to provide som hiding spaces, etc for the fish, it could be even much more than what I see on the photo. But often it is also very helpfull to keep only the male and female together in a much smaller tank, -such as 12 liter, and give them the opportunity to find a cave.
The water quality also plays a part, – what kind of water do you use, do you know what the ph is and how hard / soft the water is ?
It sounds really interesting that you are getting even more parosphromenus, – however, we are always a bit sceptical when the fish are sold as deissneri in the shop. It is very rarely, or in fact never, the ‘true’ deissneri. But it is always some other interesting species, – so when you get them, it would be interesting to see photoes of them, and then we might help you to find out if it is the true deissneri, or if not, which species is it then.
But please feel free to ask any kind of questions, we are happy to help what we can..