Now that the basic parts of the aquaponics system is in place and there is a cover over the entire thing, it is time to set up the grow beds. The grow beds exist so that we can take the water from the fish growing area and run it through an area where edible plant can grow that will take out waste products produced by the fish from the water and use them as nutrients for growth.
The grow beds can be set up to maintain the water level or fill with water then drain out into the fish pond area (flood and drain), either way the water is continually pumped from the fish area to the grow beds. My system is set up to be flood and drain and to achieve this drain through a bell siphon, to make one see the article in this section.
Due to their robustness, availability, cheap price, volume and general ease to work with, my grow beds are two recycled steel baths. If I were not using baths I would have to drill holes in the bottom of the grow bed wide enough to take the feed pipe from the bottom of the bell siphon. The baths come with already a drain plug assembly already in place and it only remains to unscrew the bottom plastic nut from the bottom of the bath to allow the drain plug assembly to be removed. If, as it was in my case, the nut is seized take your favourite angle grinder and make vertical cuts in the nut, allowing it to be split off and the drain plug assembly to be removed from the plug hole. You should not have an open plug hole.
After removing the drain plug assembly and before fitting the bell siphon I thoroughly cleaned the plug hole area which had a accumulation of gunge in it and to get a good seal it is critical that the area is clean and dry. I unscrewed the retaining nut and smooth washer from the threaded bottom of the part of the siphon that protrudes through the hole, I placed the siphon through the hole and made sure the ridged washer on top which comes in contact with the edge of the hole was ridge side down, so ensure a good seal. I then screwed the retaining nut home until it was finger tight and ran a bead of silicone around both sides to ensure a seal.
With the bell siphon in place, I put a layer of 20mm gravel on the bottom of the bath and around the bell siphon itself to improve the drainage. I then filled the baths up to within 50mm or so of the rim with 10mm gravel, which is cheap and easy to get. The expanded clay balls work well and look good but are very expensive, but the gravel does the job. If you can, wash out any fines from the gravel before you put it in your grow beds. The gravel works well but my lovely wife was not satisfied with how it looked so I got hold of 3 x 15kg hags of the volcanic rock scoria and put it on top; it filled up the baths to the rim totally and look really good. I had the tick of approval from the boss!
