For one thing they keep the water clean. Also they make the tank look much prettier.

一则它们可以使水保持清洁，再则它们可以使水箱看起来更漂亮。

youdao

For one thing they keep the water clean. Also they make the tank look much prettier.

一则它们可以使水保持清洁，再则它们可以使水箱看起来更漂亮。

youdao