Expandable Hydroponics System from Junk - Flood and Drain

Step 5 Removable Planter Bag - Optional but handy

Poke many holes in an empty milk bag large enough for good drainage, but too small for growing medium to escape. A drywall screw worked for me.

Fill with medium and place in finished unit.

Handy for transplanting or system maintenance. It is also MUCH easier to see the water level due to the air space around the bag.