The plastic area on bottom is a reservoir where nutrients like "Thrive" are fed into after mixing with water. One full Box of Thrive for the set up you see every two months. Then as plants mature you don't need any more.
The boxes on top are filled with sawdust as a medium to hold plants.
An extra feed of Iron can be beneficial. (Iron Chelate) Mix one tablespoon with bucket of water and add. Only need to do once when plants 3/4 grown. Or add when and if you see some yellowing in the leaves. Potatoes in particular.
The roots of the plants go through a wire netting on bottom of boxes into the medium. Use thin layer of wood wool first to stop sawdust falling through wire netting. Half inch Bird Wire good for this bottom.
Make sure there is no light able to penetrate into the reservoir or alga will grow. Boxes tight together and right to edges of reservoir. Measure and make boxes after reservoir set up so all fits exact.
At the rear of the set up is an overflow pipe for when it rains and also at a position that keeps at least a half inch gap between water in reservoir and bottom of box so plants don't drown.
Bad salts will build up but not till everything harvested anyway.
You then need to clean out the reservoir to start again with fresh water and fresh sawdust. Wait till roots go through into reservoir prior to adding the nutrient. In the meantime feed with watering can with nutrients in as you would in normal gardening.
Just an addition; I used painters planks for the reservoir box then made the pool with plastic sheeting to hold the water/nutrient in case you are wondering how bottom reservoir made. Very important no holes and that overflow pipe put into a position keeping water at 1/2 to 1 inch below bottom of boxes.
Re potatoes; Top box has no bottom. Just used to give more height to single bottom box as potatoes grow to add more sawdust. Found two box height ample re growing cycle.
Regards
Retro
Subject: Hydroponics 
Sun Aug 12, 2012 1:42 am
