"Goldfish catching" is one of the traditional YATAI from the old days. You catch goldfish from the water tank with the tool called POI which shape is like a magnifying glass and has very thin paper instead of a lens.
If you wait for the timing slowly sinking a poi in the water, the paper can be torn but if you try to catch quickly, again, paper can be torn. Those who good at catching goldfish, they seem to know the trick.
Even if you can't catch any, don't worry because you'll get some in the end.