At 7.10.20 I went to the pet shop to have a chat. I came back with three snails [one red-rimmed melania (Melanoides tuberculata) and two Dusky Nerits (Neritina pulligera), four little Yamato shrimps (Caridina multidentata), a plant called spade-leaf sword (Echinodorus cordifolius), and a spherical alga called Marimo moss ball (Aegagropila linnaei). I use the opportunity to make an inventory of the visible biota of the aquarium.

I already tried different plants in the aquarium. Many of them didn’t flourish under the given conditions. Sometimes they thrived at the beginning, but later they got shabby. Are they sensitive bioindicators?

The Eurasian watermilfoil (Myriophyllum spicatum) which I fished up out of the Danube, is obviously growing well under the given conditions.

The Java fern does not look well. I’ve read that dark spots can appear on older leaves if there is a lack of potassium.