This is the 12616th most frequent German word.
welsen
The German word "welsen" means "to catch catfish" or "to fish for catfish."
In this sentence, 'Welsen' refers to catfish as a species commonly kept in aquariums.
Ich habe die Welsen im Aquarium gefüttert.
I fed the catfish in the aquarium.
Here, 'Wels' describes an individual of the catfish species caught during angling.
Beim Angeln am Fluss habe ich einen großen Wels gefangen.
While fishing at the river, I caught a big catfish.
This usage shows the plural form 'Welsen' to collectively refer to catfish present in a natural body of water.