Wednesday, July 4, 2012

Building an Aquaponic Biofilter for $40 or less

Homemade biofilter creates aquaponic magic!
A biofilter is a key component for success with your aquaponics system. The secret to a phenomenal aquaponic system is creating a colony of helpful bacteria that help eliminate the ammonia that is harmful to fish and convert it to nitrates that create a healthy system for the plants to thrive. A biofilter helps make this happen.

Here's a few simple steps and tips to help you build your own aquaponic biofilter for less than $40.

Note: My filter uses a 1/2 inch intake (from a small pump) and a 1" output. You could easily double that by using a 1" intake and a 1 1/2"-2" output.

1A: 1" PVC to two elbows create a "swirl"

Supplies List
5 gallon bucket
1" sch. 40 PVC elbows
1" PVC T
1" bulkhead
4" of 1/2" drain hose
1/2" bulkhead
16" PVC 1"
3" PVC 1"
(note: most of my PVC pieces were scrap)
Some sort of a ball valve for the bottom drain
2 Media screens (I used bucket lids and drilled)
Media (I use a combination of bioballs and hydroton)
Aquatic tank filter material (I use Matala filter)

First, I drilled the hole for the 1/2" output drain (for sediment) and added a drain hose and ball valve, as low as I could get it on the bucket (see top photo). I drilled the larger hole for the 1" output drain close to the top of the bucket (I had a scrap bulkhead - may look funny).

I built the PVC piece pictured in figure 1A. I'll cover this with media screen (about 2" up from the bottom of the bucket) to allow an area for particles to settle. I can use the valve on the 1/2" output to drain/clean the sediment. I'll pour directly into our outdoor gardens or pour through the wormbeds, as this area is typically full of fish poop.

Media screen made from extra bucket lid.
I bought a couple extra 5 gallon bucket lids at home depot for $2 each. After cutting them to fit with a jigsaw and drilling holes, they make perfect media screens (one for below the media and one for above).

I put the lower screen in place and cut some of the matala filter material into a circle (snug fit) above the bottom media screen. Followed by adding 2 gallons of blue bioballs (a product that has a lot of surface area for bacteria to grow on) and covered with hydroton, some of which already had bacteria from my other system. The bacteria will form on it's own, but takes much longer.

Note: I'm testing out this product (bioballs). You could probably make due with hydroton or even pea gravel, etc. The important part is having lots of surface area on your media.

I'm experimenting with the idea of topping off the bucket with hydroton and putting plants in here. Just a thought. I'm sure it works great either way.

The hydroton already has bacteria growing in it.
I put the second media screen on the top and allow about 3" of space between the top of the media and drain. Just treated water flows in this area, and will make it's way out of the filter through the 1" output and to the raft tanks (hopefully, full of nitrates).

I put the lid on and added the 90 degree elbow to the 1" input tube. I had to add an adapter for the 1/2" hose that will bring water up from the tank below. The water will flow down the tube and swirl out the solids in the bottom of the bucket. Then the water (full of ammonia) will rise through the media and the helpful bacteria will convert ammonia to useable nitrates.

I may try and add another matala filter
below the media screen
The output tube can flow out into grow beds or in this case into a deep water culture table with floating rafts.

I needed to add an adapter to work with 1/2" input.


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  4. Scott;
    Thank you for this cool DIY. I hope to have one up and running soon.
    Just a couple of questions if you don't mind.
    Would it be feasible to use 1/2" PVC for the intake and a 1" discharge? The reason I ask is you mentioned (scraps laying around.)
    You don't use a air stone? Last but not least. Do you think a unit this size will take care of a 8 bucket RDWC units,aproxamently 36 gallons.
    Thank You.

  5. Sonofdust -
    We added an airstone. I also pulled the lid off and topped it off with hydroton. i stuck a few plants in there, too. I might try two of these for a 36 gallon set up. I use it to feed my NFT system, normally, although we are about to redesign for 2013. I'll blog once we get started.
    We've abandoned the aquaponic pond. I'm trying organic/hydroponics, using worm/compost teas and other organic nutrients.

  6. Looking forward to seeing your projects for 2013 Scott.
    I'm still waiting on the Bio Ball before I can get rolling.
    I built one like yours except, I used a 1/2" T on top (intake) and inserted a plug. Now if I need to add more Bennie's, kill the pump, pop the plug and add back.
    I thought I'd use clay balls until the Bio Balls get here. I reversed intake and discharge and made in a closed system just to see how fast the Bennie's multiply. Hope I'm on the right track.

  7. Exciting. Glad it's working out. I've been slow to start, this year. I do have lots of starts going. I've lost my greenhouse space (and pond). I'm relocating to my yard, but am relatively unsure what I might end up with.
    I'll blog when I get rollin.

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