[Peter Finke]

Patrick, you wrote: “We cannot copy the natural systems”. That’s true and false at the same time, it’s a matter of speaking explicitely or not. We must try to copy the natural systems, but we cannot achieve that for hundred percents but much less. The Parosphromenus aquarium allows us a better relation than the standard tank, because the small fish eat less and produce less waste than the average fish in the standard. The absence of any dried food is a big help. I have 33 12-liter-tanks, each with a pair of licorice, and some with small young. The plants that I use, especially swimming Ceratopteris and javamoss and some others in accordance with few live food allow me to keep the water conditions rather stable without a water change every week. And that without any filter. The tanks develop differently; there are some germ densities extremely low in which I don’t change the water for some monthes, others (with growing young fish) must be cared for more often.
Of course, I cannot care for the needs of many plants that I don’t use in such tanks. Otherwise I would have to add Fe (the two-valued), Mn and tracer elements. In aquaria, despite all nice theories, you have often a conflict between plant’s need and fish’s needs; but it is not great a problem in the standard tanks. Fish and plants there are used to rather big leaps great differences in mineral’s concentration.
But it’s true – and we agree with each other again – that to achieve a Paro-tank without any filter developing rather stable for a time as long as possible you need assorted plants and a very thoughtful and sparse feeding. But maybe we disagree again when it comes to plant fertilization. For me in my very small breeding tanks specialized for the licorice, plant fertilization is out. And for my carefully selected plant species it is unnecessary at all.