Label the picture. Write the name next to each letter.
A cutaway of an aquaponics system. A fish tank sits low on the left with two fish. A pump lifts water up a pipe to a grow bed full of gravel, higher on the right, where three plants grow. Their roots reach down between the stones. Every wet surface has a thin coating where bacteria live: around each stone of gravel, along the roots, inside the pipe walls, and on the inside of the tank walls. Dashed lines mark the top of the water in the tank and the bed.
A · gravel
B · roots
C · pipe walls
D · tank walls
The thin teal coating shows where bacteria live.
Answer in your own words.
Where does the Recycling Crew live?
What does the crew need from the water to do its work?
Why don't growers scrub every stone clean?
Draw or explain
Where else have you felt a slippery film on something wet? What might be living there?