After a lot of searching online and in local fish shops, and one failed attempt to buy the fish from a breeder in the next big city (Potsdam) because the breeder sold them to someone else instead of waiting a day for a reply from me, I found a listing on eBay Kleinanzeigen (a classified listing website). While not as close as my usual fish shop, the fish were only an hour away by public transport, door to door, which was an improvement on 55 km that I was thinking that I would have to travel to find the not-so-local local breeder that I had found through a forum for local fish keepers.
This breeder was only at home from 19:00, so I made an appointment to see the fish and, after becoming slightly lost looking for the entrance to the apartment block, found myself walking into a small lounge with three aquaria. The breeder asked me to sit by one of them and observe the fish inside, while he told me about how he looks after the Danios. The Danios were bold, well coloured and a healthy shape, with the females being full of eggs. In short, these were by far the best D. margaritatus I had ever seen. After 10 minutes or so, the breeder showed me the foods he uses, which were newly hatched Artemia, frozen water fleas and high-protein dry foods. He explained that the fish hatched in July, and were power fed (fed small quantities of high protein foods often) so that they were now 70% of their adult size.
After I confirmed that I was very happy with the fish, and he made sure that I had the details for his frozen foods supplier, he started catching out the fish into a bucket, while I observed his other aquariums. He had a lovely nano aquarium, which was suspended from the wall, containing a beautiful pair of young Badis badis, a planted 2 metre aquarium with Pterophyllum scalare and Paracheirodon axelrodi, and a rack of breeding aquariums, one of which contained Hemiramphidae (halfbeaks).
Once the breeder had the 10 Danios in a bucket, I counted them and he proceeded to transfer them to the fish bag that I had brought along. Since the journey was short and it was 20:00 by this time (so quite cold, around 5-10 °C), the fish were packed with 90% water and 10% air. Under normal conditions, for example form an fish shop or for long journeys, the fish would be packed with 10-25% water and the rest air, as the oxygen that is in the bag is all that the fish will have for breathing for the whole journey. Once the fish were double bagged, I paid the breeder and headed home.
The trip home took slightly longer than expected as one of the trams was late, but because of the unusually high volume of water and a few layers of bags between fish and air, the water did not chill much. I arrived home at around 21:00 and proceeded to drip acclimatise the fish, which took 3 hours. Unfortunately, I forgot to test the water parameters for the record, but I expect that the breeder has roughly the same water as me given that he pointed out that he uses tap water. Once the bucket was full, I transferred the 7 males and 3 females to the aquarium, topped it up with dechlorinated tap water and headed off to sleep.