Good this comes up. I just spotted some P. bintan “Sentang” fry of about 1cm in my meter tank with Apistogramma and Dicrossus. I’m sure there are a lot more hiding in the big Ceratopteris since they spawn regularly.
I actually think paro’s do fine in bigger tanks if you allow them and their young to hide, although the adults rarely will do so. They are way more active and beautiful in bigger tanks. Also they seem to do a lot better when other species are around.
In most tanks I have a small filter for making sure oxygen is provided, for both fish and tank floor(which is covered with leaves) to prevent anaerobic reduction of waste. In most tanks with only labyrinths(I also keep wild Betta) there’s no filter at all, since they breathe air. In two of my tanks the filter a lot of filter material compared to pump capacity. In this way there isn’t too much water movement in both filter and tank, but most organic waste will be broken down by bacteria. In these two tanks conductivity stays very low. In fact, it doesn’t rise at all, even without any water changing.