All who write here on Cryptocoryne should read carefully what has been written in this forum and in the general information in the PP.
Very short:
– Yes, there are typical blackwater Cryptocoryne species. But apart from the fact that they are not traded in the aquarium shops (because they are extremely difficult to cultivate, see below) you cannot cultivate them in a normal Parosphromenus-blackwater tank.
– The species that are cultivated and traded are no blackwater species. They sometimes stand a Paro-tank-milieu for a certain time, but they don’t thrive there.
– What is the problem? The problem is the structure of an aquarium: a still-water tank without a constant supply of nutrients from the soil to the roots of the plants. A streaming filter does not change that. In a natural water that is factually nearly without minerals and other nutrients, plants must receive their mineral energies by their roots. Most blackwater habitats are without submerged plants, especially those which receive their nutrients by the roots. But sometimes, you nevertheless find fields of thriving blackwater species, often Cryptocoryne (as fuscus, pallidinervia, bullosa and others). Why? Because at all these places there are streaming “nutrient fountains” in the ground, slowly but constantly delivering the necessary nutrients that are missing in the blackwater. Nobody has managed to imitate this in the aquarium yet; a mild heating from below cannot fulfill the needs (only in a normal aquarium with normal Cryptocoryne).
– Therefore: The only efficient way of cultivating blackwater Cryptocoryne up to now is emerse culture within a wrotten beech leave-ground. But here, the leaves of the plant remain above water surface.
This does not mean that cultivating blackwater Cryptocoryne is impossible forever. But it is a matter of fact that despite many experiments of the best cultivateurs and specialists of that plants (Horst, de Wit, Bastmeijer etc.) the problem is unsolved up to now. One should know this; it’s not only finding the right species, but knowledge of the differences of structure between nature and the small thing called aquarium.