[Peter Finke]

Jacob, it certainly is a good thing to reflect as you do on establishing a blackwater aquarium, since that’s a pretentious type of tank. But I think there are limits to the planning of a system on the theoretical level; only in practice you will finally see if it works. I think it could, with one exception: your idea of “heavy planting”. You can manage an aquarium with less special water conditions very well by using the hygienic powers of many thriving plants, but in a blackwater system you will not be successful. There are two reasons for it: first, most plants do not stand very low pH-values and very low conductivity values. Second, they need nutrients. But their constant input and the biological activity of the plants will force those values up and down and everything becomes instable. More important than the absolute value is stability of the milieu. Well growing plants constantly influence the water conditons and it is very difficult to master that. If not impossible. In a “normal aquarium” you can manage that because the fish are not as delicate and the water values allow more swing. But in a blackwater system it becomes very difficult to integrate the interests of fish and plants. One has to accept that there are structural limits of aquaria in comparison to the natural biotopes of licorice or chocolate gouramis.
Instead of thinking of ever more complicated technical solutions you should try things out practically. It is easier than you think now to organize a rather stable blackwater aquarium. I have many small tanks (12 liter, 25 liter) with mostly only Vesicularia and Ceratopteris, an almond leaf at the back, old wood from peat bogs and some oak- or beech leaves at the bottom, and with water with pH between 3.5 and 6.5. and 20 to 80 Mikrosiemens/cm, and there are licorice gouramis thriving and propagating. There is no filter at all, but I change some water every two weeks. This is rather simple a system, and conditions are stable. For chocolates you need the tanks a little bigger, OK, and that will work. A little water flow is very good, but that’s all.