This is the 8736th most frequent Russian word.
песчаного
"Sandy."
The word 'песчаного' is an adjective derived from 'песок' (sand), describing the soil near the river as sandy.
Я видел много песчаного грунта возле реки.
I saw a lot of sandy soil near the river.
Here, 'песчаного' is used as a color descriptor, indicating that the sand in the terrarium is of a sandy hue.
У меня дома есть террариум с песчаного цвета песком.
I have a terrarium at home with sand of sandy color.
In this sentence, 'песчаного' describes the shore as having a sandy composition, providing a contextual setting.