In order to keep tadpoles I bought a fish tank for 525 yen ($5.53 €4.20). Its size is 30 cm * 20 cm * 20 cm.
It is made by plastic. You can feed small fish or insects in this tank.
Frog is a common creature in Japan. I captured tadpoles from a small water spring near my house last week.
If you want to know something, ask me please.