Aquaponics Pond Filter

Legs

ADC
Book Reviewer
I'm finding that a standard 'off the shelf' filter can't keep up with my little duckpond and my three ducks. I've thought of a new system that uses gravel and sand, but allows me to grow veggies using the water in an aquaponics system. The nutrients from the water feed the veggies, and the gravel and sand layers clean the water before returning it to the pond.

As so:
Aquaponics filter.jpg



I hope this makes sense.

So... What grades of gravel and sand will I need for the two aquaponics filter beds? Do I need two filter beds? Any further advice?
 
I'm finding that a standard 'off the shelf' filter can't keep up with my little duckpond and my three ducks. I've thought of a new system that uses gravel and sand, but allows me to grow veggies using the water in an aquaponics system. The nutrients from the water feed the veggies, and the gravel and sand layers clean the water before returning it to the pond.

As so: View attachment 214715


I hope this makes sense.

So... What grades of gravel and sand will I need for the two aquaponics filter beds? Do I need two filter beds? Any further advice?
Legs, P, I wish the stuff that keeps you awake at night did the same to me :) Sounds like you're doing it right. I'd get some of those rice pancakes, some cucumber batons and some spring onion sliced along, with some hoisin sauce, perhaps move on to hydroponics and work up an appetite :)
 
The best media for growing hydroponics is clay pebbles; these are baked clay, pH neutral made specially for the job. Use washed filter and for the sand layer (get it from a swimming pool supplier online).

A minor design change; flow in at the top, out at the bottom isn't good design as it will erode the filter medium immediately below the pipe, cause uneven loading of the filter and won't protect from over flow.

Run your inlet pipes to the sand beds to the bottom of each tank and making a simple diffuser manifold from PVC pipe - just drill holes every couple of cm or so. Cover this with a layer of pea gravel to a depth of 4 cm or so. Before installing the pea gravel, wash it until the water runs clear. Once your gravel is in, fill the tank with water before adding the sand; it stops you getting air pockets in the filter. Then add your clay on top of the sand. Some people put a geo-textile between the pebbles and sand to completely eliminate the possibility of sand blocking the diffuser.

Take the outlet flow from the top of each filter tank as an overflow outlet. That way, you flow clean, process water out and your plant grow in filtered water.
 

Legs

ADC
Book Reviewer
The best media for growing hydroponics is clay pebbles; these are baked clay, pH neutral made specially for the job. Use washed filter and for the sand layer (get it from a swimming pool supplier online).

A minor design change; flow in at the top, out at the bottom isn't good design as it will erode the filter medium immediately below the pipe, cause uneven loading of the filter and won't protect from over flow.

Run your inlet pipes to the sand beds to the bottom of each tank and making a simple diffuser manifold from PVC pipe - just drill holes every couple of cm or so. Cover this with a layer of pea gravel to a depth of 4 cm or so. Before installing the pea gravel, wash it until the water runs clear. Once your gravel is in, fill the tank with water before adding the sand; it stops you getting air pockets in the filter. Then add your clay on top of the sand. Some people put a geo-textile between the pebbles and sand to completely eliminate the possibility of sand blocking the diffuser.

Take the outlet flow from the top of each filter tank as an overflow outlet. That way, you flow clean, process water out and your plant grow in filtered water.

Thanks for that. Could this cause any 'back flow' issues, ie the water flowing into the bottom of the filter bed backs up to the inlet pipe?

Does this produce clean water as I hope it will?

How big do the filter beds need to be for a pond of 102 gallons (460 Liters)?
 
A properly designed and set up sand filter is a very effective means of cleaning water; they can be used to produce drinking water.

The key to proper set up is slow flow, because you need time for the bacterial "slime" to grow on the sand and for the water to be in contact with the bacteria. The killer is muddy inlet water; you may need to filter this through coarser sand.

Most slow sand filters are cylinders; tall rather than broad. The common garden design is shaped like a 50 gallon drum; often they use a 50 gallon plastic chemical drum. The flow goes in at the bottom, out over a baffle plate or weir at the top. This is important; the filter needs a constant level of water above the medium.

Hydroponic tanks are different; you need surface area and through flow, not the almost static water in a drum sand filter. Think bathtub shape; in fact, people often use old baths to make a hydroponic filter for a pond. Again, water in at the bottom, take it off at the top with a weir baffle (a 6" tube over the plug hole set so the top is at the level you want the tank to run at works well).

So, on reflection. I think you need to revise your design. Top tank is a (relatively) shallow, broad tank filled with clay balls and used to grow your lettuce. This will do the coarse filter job. Centre tank is a sand filter only; relatively tall and narrow. The top tank will therefore act as a header tank for the sand filter, giving constant head and eliminating the back flow issue.
 

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