Small stones for a fish tank = 105 yen ($1.06 €0.81)

I bought a pack of small stones for my fish tank for 105 yen ($1.06 €0.81) at 100 yen shop.

Some of you may wonder why I bought stones. You may think  "why don't you pick up stones around the house?" You are right, but in Tokyo it is slightly hard to find a nobody's stone around my house. We do not have nature commons much.