cheapest diy aquaponics
There are two types of aquaponic growbeds:
- floating raft (plants floating with their roots in a constant stream of water)
- media-based growbeds (plants growing in some sort of rock/sand/gravel/beads)
Media-based systems are recommended for home hydroponicists because they are simpler and more reliable. Media-based systems are also referred to as flood and drain. The idea is you flood the growbed with the fish water (delivering nutrients and, um, water), then let it drain out (bathing the roots in air/oxygen).
Of the various ways to flood/drain a media-based growbed, the one that is easiest on the checkbook is a bell siphon. All a bell siphon needs are simple plumbing bits available at any hardware store. Oh, and a small pump. I loved the way the folks at ecofilms explain it:
"If the pump is the heart of an aquaponics system, then the auto-siphon are it’s lungs. A vital part of kit. Remember when you were a little kid and the teacher told you about the regular flooding of the Nile river and how fertile the Nile delta was to early farmers. Well think of the auto siphon as a kind of similar concept. It’s main purpose is to flood the grow bed drawing rich oxygen into the depths of the trough, oxygenating the plant roots and turbo charging the bacteria to do their thing."
They created a great animation of how a bell siphon works. A real-life system takes many times longer to fill than the time to drain (my system takes 10 minutes to fill and 1 minute to drain, ignoring the dribbly parts at the beginning and end of the siphon). Also, the pump never turns off. I found the growbed in my system only needs 10 gallons to fill the spaces between the rocks, so the change in the level of the water in the fish tank is only 2-3 inches, about 10%.
Though I love the idea of "constant height of pond" (CHOP), the added complexity and space to achieve CHOP didnt make sense for my 3x5 system. Let me tell you the bits I used to create the system Ive got.
First is the pump - 140 gallon Pondmaster that I got from a local hardware store for under $40. It has only one moving part and consumes just 10 watts. Its like having a night light plugged into a wall socket, as far as energy usage is concerned.
Next are the plumbing bits (I presume the kind of handyman attempting this will already have saws and drills, etc.). The plumbing bits are:
1) The outer sheath or media guard. Its the white tube poking up through the gravel in this picture.
This is 3" (ID) pipe roughly 1 long with dozens of 1/4" holes to allow water (but not rocks) to reach the siphon. I drilled down 12 lines, putting a hole every inch and precisely staggered the holes on adjacent lines because Im OCD. But the regular holes also serve as a crude measuring stick, helping me determine critical distances. Turns out a 15.5 oz can fits nicely inside this sheath, to prevent rocks from falling in from above. Plus a can adds iron to your system as it rusts - useful as most fish food lacks the kind of iron levels wed like to have in foods we eat.
Update - Turns out you can simply cut slices in the media guard - slices also work just fine for the base of the bell. FWIW, I use a crochet hook to pull the bell out of the media guard when I want to check the siphon.
2) The bulkhead. I used 3/4" electrical PVC fittings here, because the electrical fittings are dirt cheap and adequate to this low-pressure task. I was inspired by Richard Kinchs post"An Improvised PVC Bulkhead Fitting forLiquid Storage Tanks. I only used the PVC male and female electrical conduit adapters - I didnt need to modify them in any way. This part of my system drove me to 3/4" piping, because the 1" adapters have seams running up through the threads and dont seat nearly as well. As 3/4" is the size of standard bilge pump line, I figured it was large enough for my purposes.
I used a 1" bit to drill the hole through the bottom of my grow bed, and a doorknob hole cutter to drill a hole in the shelf for the drain. You can improve the seal through the grow bed with silicon or you can simply use a #18 o-ring. I used aluminum foil tape to seal the edge of the hole through the shelf just in case there were a leak, to mitigate moisture getting into the wood and turning it soft.
3) The 1" to 3/4" reducer and standpipe. I struggled long and hard on this bit, inspired by Affnans Bell Siphon video:
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