Sometime you may find that paroes can spawn and develop the eggs even in waters that you have not paid particular attention to, as long as there is a certain softness. In fact I had sp.Sentang as well and they were one of the species that actually had several succesfull spawnings in water which was not all that low in either ph or softness. Though some of course, but when I had them I had not yet the experience that I have today, and I had lots of problems adjusting water qualities. Yet I had several fry with those fish. So it could happen.
One of the major differencies for me – with your tank to mine 🙂 – is the question of light I think. With very low lightning you cannot get the good growth of plants, which again means that you do not get the beneficial effect on the waterquality of many plants, –
The light you have is quite powerfull, is it not ?