Thanks for the answer.
There is a layer of Ceratopteris in the tank. The paros I have don’t normally use shelter, even in tanks without floating plants. Also, the specimen in question didn’t show this kind of behaviour before given day. It swam around, mostly between some stones and pieces of wood, and displayed to the female when she came out of the Ceratopteris. That day he was constantly chasing her and kept flaring and dancing around her, so I was excited when the day after he stayed in his cave all the time.
I’ll keep watching them and looking for fry. I’ll pour some vinegar eels in every now and then just to be sure. The fry of one of my other bintan-forms seemed to greatly benefit from floating Ceratopteris and stay hidden in it, so I will keep looking in it.