Backyard Aquaponics
A place to discuss aquaponics

Been a while since I've been on this forum, but I'm still very much into aquaponics!

In 2007, I built a small AP system in my father's backyard (thread). It didn't perform too well on the plant side, probably due to a low amount of sunlight. Maintenance however was very low and it did produce quite some strawberries multiple times a year. I moved out of my father's place and the system is no longer running since last year.

Recently I did my BSc-thesis on modelling the nitrogen cycles and greenhouse climate of the INAPRO-aquaponic system. An article on my model was published last month. I'm now in my Master's, and for an internship, I also worked on aquaponics after another BYAP member recommended me (thanks Ichsani!). I just finished the internship at the FishGlassHouse of Rostock University (Germany). Their research system houses some 2000 African catfish and 600 m² of hydroponic cabins. I managed the RAS system, I researched the effect of intensive and extensive aquaponics water vs artificially fertilised water on potted basil and mint plants, and I did a small research on filtration by freshwater mussels.

Back home from the internship, I decided that I want an aquaponics system of my own again. I managed to convince my house mates in the student house and now I'm building an indoor system.


The fish loop will consist of a 120 liter aquarium with tilapia on top, overflowing into a 7 liter static upflow filter (SUF) with small plastic balls, then flowing down to a trickling filter with larger plastic balls and finally into a 45 liter sump before being pumped back to the fish. I hope to make the SUF self-cleaning with an airline and an actuated valve, dumping the accumulated sludge daily into a biosand filter.

The plants will be on a simple ebb & flow table. Two small pumps will pump filtered water from the sump to the plant table and back to the trickling filter a couple of times per day. Lighting will come from white and red/blue LED lamps. The plants will be in small plastic pots with unfertilised soil, after my experience in Rostock. I think we'll grow mostly herbs. Kitchen herbs, not Mary Jane.


Updates with photos will follow when I receive the filter parts

Awesome to hear of your education based on aquaponics. Please keep us in the loop.

Thanks, I will

Here are some pictures!

Nice to see a fellow Wageningen citizen/student on here haha. The filtering system sounds impressive.

Verstuurd vanaf mijn LG-D855 met Tapatalk

I didn't check if my pipe and filter dimensions would be sufficient before ordering the parts, so I'm doing that now. Warning: I'm thinking out loud and it gets a little technical.

Pipe head loss
I'm aiming for an aquarium turnover of about 6 times per hour. That means a flow rate of 750 l/h through the fish loop, with 800 mm static head for the gravity return flow. I chose 18x22 mm diameter tubing for the overflow and to connect the filters. This would result in a flow rate of 0.8 m/s in the tubing; that should be enough to keep it from clogging.
At 750 l/h flow, 18 mm ID straight plastic hose has about 55 mm head loss per meter. In this system, that's about 110 mm head loss through the overflow and 55 mm head loss from the SUF to the trickling filter. Let's make that 200 mm including a few bends and possible biofilm buildup; then the tubing alone takes up 25% of the total available head.
So I think I'll make at least the overflow from 32 mm PVC pipe and fittings instead. Then the head loss to the SUF should only be about 50 mm.

Static upflow filter (SUF) head loss and capacity
The SUF has an inner diameter of about 105mm, so with a flow rate of 750 l/h the upflow velocity is about 87 m/h. I hope that's low enough to keep the media static. Above a certain velocity the filter might become a moving bed filter. I've read that industrial upflow filters run at only 1-30 m/h so my SUF might be a bit undersized or overloaded
The head loss of the media is dificult to calculate as it depends on sludge buildup. I'll use about 5 liters of plastic biocarrier (similar to Kaldnes K1). Liao & Ødegaard (2002) found that Kaldnes K1 in an upflow filter running at 30 m/h has almost 100 mm of head loss per gram per liter accumulated sludge. Assuming the specific head loss increases linearly with flow velocity, at my flow rate the head loss would be 300 mm per gram per liter accumulated sludge. So with 5 liters of media, my SUF can only catch 5 grams of solids before head loss exceeds 300 mm. I was hoping for the filter systems to be able to handle at the very least 10 grams of feed input per day, which would correspond to roughly 5 grams of solids, so I expect about 300 mm head loss if I backwash daily. I should however keep as much reserve head as possible to prevent overflowing of the aquarium. Maybe I should control the automatic backwashing with a float switch at 300 mm head loss.
Since my SUF design still has some room at the inlet in the bottom, I might try making a small radial flow filter (RFF) "hood" to settle some more particles before flowing up through the media. This would use up some head but may slow down media clogging.

Automatic cleaning of SUF
I'll have to mount the SUF much lower than I thought due to the head loss. When the main loop is done, I'll start with the automatic backwash system for the SUF. I hope I can still manage to dump the backwash by gravity into a biosand filter but there may not be enough height under the SUF left for that.

Trickling filter
There will not be much gravity head left for the trickling filter either, so I will make it a bit thinner and wider than I had initially planned. The large bioballs that I've ordered (36 mm diameter) have little spunges inside so they should have plenty of surface area for nitrification, besides, the 5 liters of media in the SUF should already be plenty for nitrification even though it's not aerated. I'm more concerned about gas exchange, but I can always add air stones.

Head distribution overview
So the 800 mm gravity head will be roughly distributed as follows:
55 mm: head loss of aquarium overflow and tubing to SUF
300 mm: expected max. SUF head loss
190 mm: reserve for SUF
55 mm: head loss in tubing from SUF to trickling filter
200 mm: trickling filter

If I change my overflow to 32 mm PVC and if the media in the SUF stays static at this flow rate, I think everything should still work out.

I finished the no-holes-overflow (NHO) in 32 mm PVC. The static upflow filter (SUF) is almost done as well - just need the biocarrier media and some mesh to keep it in place. I've added a removable 32 mm pipe and 50 to 60 mm cap to turn the bottom part into a radial flow filter (RFF). I can reach it from the top and remove it, should that not work.

The SUF has two inputs and two outputs. The regular input and output (20 mm hose barbs) are on the 45° branch. For backwashing, the bottom houses a 10 mm hose barb for an airline and (when it arrives) a 32 mm ball valve for emptying.

As you can see in the first picture, I can't create the head room that I wanted for the SUF because then it would need to go through the floor. I can place it as low as possible but that would only give 300 mm head room including the NHO, leaving about 250 mm head room for the SUF. So it might clog up too fast even with daily cleaning when the tilapia are larger. I could of course clean it more often if that's needed. I've added a second barb on the end of the NHO to create another overflow in case the SUF head loss becomes too much. So I'm no longer worried about the head loss.
Draining the SUF automatically will be difficult though; can't use gravity any more. I'll have to think of something else

Trickling filter is ready for testing.


Still waiting for one order which includes the hoses and pumps so I can't hook anything up for testing yet

The LEDs for the plant part. Power draw is 40W. The 10 lamps in total have 25 warm white LEDs, 17 red LEDs and 8 blue LEDs. They're in standard GU10 fittings so the lamps are easy to exchange if I want different colours/ratios.