Setting up a low-current tank for gouramis
What do experts think about bottom ground consisting of pond soil, I tried this in my current tank and had generally good experiences (after appropriate activation period of the filter).
I generally do not recommend using soil including pond soil in aquariums. Some kinds of soil are very rich in nutrients (however, this rather applies to topsoil than pond soil); but above all, soil often has a rather heterogenous grain size and therefore tends to clog. Fine (approx. 2 mm grain size), round grained gravel or round grained sand, both with rather homogenous grain sizes, are ideal.
I would also like to know whether installing a water pump is necessary in an L-shaped tank. I wish to keep gouramis and fish from similar origins.
Hardly any water current is necessary/advisable in this case; water agitation by the filter is usually sufficient. However, it is advisable to install a second (weak) pump in densely planted tanks or in ones decorated with plenty of rocks/roots, as to prevent the formation of still water zones.
Is there experience with water lilies in an aquarium?
Yes, this is not too uncommon: The popular "Tiger lotus" (Nymphaea lotus) plants are, after all, nothing but a water lily species kept in aquariums. Sometimes they even grow blooms, however only in open tanks.
Dr. Bodo Schnell