Hi Tomaz,
Welcome to the world of freshwater fungi, with several undescribed species. I don't know that one.
Your analysis is already well advanced; you have noticed that the spores of this fungus are even larger than those of Annulusmagnus triseptatus. You need to look closely at other characteristics, such as the shape and size of the apical apparatus (too small for the Annulusmagnus genus), which is generally clearly visible in Congo red, or the thickness and composition of the peridium. One of the characteristics of your fungus is that it is submerged and resembles Pseudohalonectria. You managed to see that there were two fungi, which is remarkable.
You did a great job in any case, well done!
I don't even have a genus name to suggest, but it's been a few years since I've looked closely at all the publications about freshwater fungi. Let's hope another opinion.
Alain

Hi Alain.
Thanks for taking time to have a look at my photos. I guess I was also a bit lucky with discovering that there were two species by taking a random sample and finding these ascospores. I might attempt some more microscopy in the evening to try getting some more data, like perithecia section. Interestingly I randomly looked at some photographs of Pseudohalonectria now online and stumbled uppon a species called Pseudohalonectria hampshirensis which seems to be kinda similar in a way. That would also explain why the very similar, pretty much indistinguishable, macro appearance with spore deposits being almost exactly same color as the Pseudohalonectria. I wonder if they are related…
All the best!

The species you mention (which is different from yours), and the other recently published species discovered in recent years, prove that this genus is not so simple and still poorly understood, assuming that it is a single genus...
Your discovery deserves to be sequenced. I encourage you to continue exploring the wonderful and still little-known world of freshwater fungi.
Alain

Adding some freshly taken micrographs. Sure looks like it's Pseudohalonectria related. Very interesting that 2 species shared the same stick. No wonder I couldn't tell the two apart just with hand lens. Though ostiolar neck does seem to be shorter as with the other species I found near.

Hi Tomaz,
I agree Pseudohalonectria is the suitable genus and P. hampshirenisi likely a good match.
In this genus, ascomatal morphology is often variable, especially the length of the neck which is not informative. Spore size and septation are more diagnostic but your photos show well how they swell in water on the slide. Width recorded in the first minutes is more reliable.
Cheers,Jacques

Thanks for having a look and the tips! Now I just wish I could prove this thesis.