The first sub-experiment was formally terminated without the aquarium having been cleaned. First 20. September 2021, it was decided that a normal cleaning of the aquarium could be carried out. The reason for this was that the growth of algae had increased below the surface in the bottom and on the plants in the aquarium. There were some salt deposits that had to be removed from parts of the glass walls, but otherwise the water was still completely clean and the fish seemed to thrive. The veil tails – three in number – had to a considerable extent put on weight but still seemed healthy and active.
The picture (Figure 2) below is taken 23. September 2021 The aquarium had then been left without being cleaned since 28. May 2021 ie. for almost 15 weeks. After the cleaning, the aquarium has not been allowed to deposit salts on the walls, the visibility in the water is excellent as shown in Figure 2 and the general condition of the fish is impeccable. In the next few weeks, a determination of bacteria in the water will be made as a consequence of the fish leaving feces behind. Apparently, there is an ecological balance in the water so that the small amounts of E. coli and coliform bacteria based on the faeces do not have a negative effect on the conditions in the water and at least not on the health and well-being of the fish.