Goldfish

From the theme of "Track back fellow" this week

The goldfish was kept in my home several years ago. The goldfish of various sizes had been swimming in a narrow water tank for about 20 years ago. Goldfishes in the water tank grew fast, and the number decreased afterwards, too. The last one dying several years ago became a lot of a money fish that had reduced the carp by two turns.
I think that it is a favor to raise even here to a big goldfish that cleans goldfish's roof over one's head with our (especially, dying grandfather) regular cleaning of the water tank.
The water tank doesn't exist.