Backyard Aquaponics
A place to discuss aquaponics

Dear All

First I would like to introduce myself. I am based in Namibia, have mechanical engineering background, a qualified aircraft engineer and is currently a air transport pilot flying small and medium aircraft all over Africa.

I have always been interested to building projects, growing vegetables and love keeping fish. My wife though do not like fish tanks in the house, since she has to feed them when I away. I can spend many hours just watching the fish.

I have been researching hydroponics and aquaponics for a while now and have decided to take the plunge and set up a system in my backyard.

In Namibia due to the water scarcity growing vegetables in a aquaponic system is the best solution, also fresh vegetables is ridiculously expensive and a lot of times only frozen is all that is available.

The system I am planning to build will be set up in a 5x4 meter area in my backyard, we have enough sun, however I will have to put it in a grow room enclosed in net, otherwise the birds will just decimate all the produce and even the leaves, this I have learnt the hard way with my previous attempts at planting vegetables.

The proposed system will be a 1000L fish tank (CHFT) and a buried IBC sump (PIST) with 3x cut off IBC for grow beds with pea gravel media, with auto syphons. the system will be flood and drain; using a constant running pump in a buried IBC.

See the drawings below:

I have omitted all the supports, netting and roofing for clarity, (the roof will be clear glass fiber corrugated sheets to keep out dust and rain) there will also be a door. I hope to get tilapia, but will probably start with goldfish or Koi.

The black tank is the 1000L fish tank, the blue barrel is a swirl filter (this may be too big, may replace with a 150L barrel). It will also contain a vertical separator just around the outlet and will be between half to two thirds the depth of the barrel. The drained solids will be used in my soil vegetable garden.

In the sump will be a 2400 LPH (2.3 m head max) pump and an air pump with air stones in the fish tank, a solar panel and battery for the air pump as backup will be used.

The fish tank is on the West and should catch the last rays of the sun for some additional heat for the long winter nights. I may even add a solar water heater with a temperature regulator later.

The typical winter air temperatures at night goes as low as -1 deg celsius with daytime air temperatures as high as 35 in summer.

Once the system is up and running I plan to add growing towers or horizontal NFT tubes with a separate pump.

I hope to plant lettuce, spinach, cauliflower, broccoli, cucumbers, eggplant, cherry tomatoes and gherkins.

Most of the stuff I already have except for the poles, IBCs and plumbing.

I decided to go for pea gravel since obtaining anything else will be either very expensive or impossible here.

Please provide your input, be it negative or positive, I am willing to learn and since it will be a substantial investment in time and money, I would like to minimise basic mistakes as far as possible.

Thank you

Welcome to the forum CaptKarel

welcome CaptKarel, that schematic seems pretty reasonable.
Only comment would be that a broader shallower fish tank may be better than a deep, tall one.
Is that an actual tank that you have or just a knock-up for the sketch.

Dear dlf_Perth

Thank you for your kind words.

The fish tank I am planning to use a standard 1000L plastic tank (see attached picture). I already have a black plastic one, it is 1.3m tall and 1.14m dia.



I considered to use an IBC, but thought the round tank would be better for the fish or a horizontal tank, but this would significantly increase the setup cost, for some reason the horizontal tanks are fairly pricy.

I unfortunately am out of the country at this time and did not make a scale drawing of the tank since I don't have the actual measurements of the tank. The tank in the drawing is just a placeholder and the plumbing will have to be adapted slightly to line up with the actual connectors on the tank. I will probably do this once I am back home.

If the tank is too high to see in, I can add a small step at the base to see inside. I might have to add some LED lights to light up the inside, the black tank is very dark inside, I have been using the tank for a few years to catch rain to use for my soil vegetable garden. I can see inside without a step but not the bottom through the top hatch. Optionally I could also cut a hole in the sloping side which will provide better access.

A few questions:

1. If I startup with one grow bed and some goldfish or koi fingerlings, how many fish would you recommend?

2. I suppose planting a few easy growing vegetables like beans and spinach for the initial cycling would be recommend until the bacteria is established?

Thank you,

Here is a better view of the RFF and the SLO from the FT:



Inside the RFF is a bucket with an open bottom, how deep should this be, will half the depth of the drum be good enough?

The solids drain is designed to exit from the side, which will be better; from the side or the bottom? I have read that somebody on this forum have formed a cone inside a drum using expanding foam sealed with silicone. The RFF will be on a stand and I will have access to the bottom

You can also see the return pipe with valve just above the ST to regulate the flow into the FT.

How do I decide the correct flow? Adjust for reliable Auto Syphon function or FT volume?

If for FT volume do I have to pick a suitable size GB outflow pipe? I am planning to use 25mm dia at this time with a 50mm bell dia and 110mm dia media guard. I could go to 32mm, 40mm or even 50mm but finding 75mm pvc pipe for the bell is difficult and could only be obtained on special order from my plumbing supplier.

At a later stage I would like to add grow towers or horizontal tubes with NFT. This will be either 110mm pipe or covered upvc gutters.

Can I use another valve and T-piece to supply water from the ST for the NFT, or should I rather have a separate pump?

I am planning to install a backup pump right from the beginning with a switchover valve. I am planning to run each pump by turns every other month. Sorry this may be over engineering the system, but I can't expect the wife to change a pump if I am away on a trip.

Regarding the outflow of the water supply to the GBs; which will be better:





The idea of the spray bar is to have open ended pipe with 10-12mm holes about 50mm apart to spread the water over a larger area, better aeration, cooling, etc.

I would also like to split the upper layer of the GB media in 3-4 zones for different types of plants using offcuts of IBC plastic. This will give some guidance to the wife, she is the one with the green fingers, and also satisfy my OCD tendencies by keeping the GB "neat" The plastic barriers will only go down about half the depth into the media, with no barrier in the bottom half.

Thank you beforehand.

a full sized rainwater tank is probably a bit too large and deep for a FT.
Quite a few people here have chopped them down.

That looks like the height is around 2m or so.
You could go in half quite easily and have 2 tanks.
Most aquaculture tanks are 0.6-1.0m deep.

the circular tank would be much better than IBC etc.

The drawing is really only a place holder, did not want to draw an exact scale drawing of the real thing. The actual tank, which I already have, is 1.3m tall and 1.14 m dia.

Other options were to use an IBC tote as a fish tank or a horizontal plastic tank, which would have meant a bigger setup cost.

round tank 1.14m Dia gives 1000L at 1m deep so equivalent to an IBC in volume and much better shape.
people with round tanks have cut slots in the lids to improve access.

Hi Darren

I will probably cut out the two quarter panels next to each other while keeping some support in between. I might even remove the whole top and make a hinged cover for the top.

I have managed to find a very close 3d model of my tank in the sketchup library, I also found some other useful components. Credit to Tristrin for the nice GB models. See the updated pics.

I suppose the tank will have some temp differential from the top to the bottom but since it does get quite hot here in summer (28-35 deg C) I hope to keep the lower part ot the tank at a lower temp and with a high DO using an airpump, in winter I will expose the tank to the sun in the afternoons, the tank is on the West side and should get nice sun in the afternoon. I will also minimise the flow through the GBs from midnight to early morning to slow down heat loss, it can to freezing point here on some days, the area in my backyard is protected on 3 sides from wind.



Here is a x-ray view of the plumbing at the sump tank, you can see the second pump with the two valves to select the active pump, if I can find two check valves I will rather use that. The upper valve is for flow control and the return comes back to the sump. This should provide enough DO if the pump is running 24/7.



Here is a x-ray view of the RFF and the plumbing, not sure if the levels are right; the idea is that the SLO from the FT will enter the RFF from the side, the water will flow spirally down and slow, dump solids and then move up in the centre well to flow over the upturned elbow, this is then delivered by gravity to the GBs.



Here is a view of the grow beds, each will have a valve and bell siphon.
The ball valve at each GB will control amount of water delivered, the second GB valve will more open than the first one, etc.
The bell siphon with 25mm dia pipe will dump in a 32mm dia drain. As far as I could determine from other posts on this forum, each siphon needs to suck air from the drain end at some point to function correctly.



If any body spots any problem or possible design fault please let me know.

Thankyou beforehand.

I don't think your RFF will work as well as it could with the piping around that way. The point of having the water enter in the centre and exit from the outer edge is that every time it spreads out, it slows down; that's what makes the settleable solids drop out. It looks kind of like you're trying to build a combination swirl filter and RFF?

Hi Mel

Thank you, it may be that I called it by the wrong name, if suppose it could be called a swirl filter.

Regarding the design I read a lot and looked at what other people have tried and went for what seems to work, did not pay much attention to the names though.

Is there a benefit to run one instead of the other, will it make a big difference, which one is more efficient for removing solids? I don't really want a filter that needs cleaning; like removable foam, mesh, etc.

Just a question: Should the inlet be above, same or below the outlet level?

I also considered popping a few bio-balls inside, if the inlet is above it should aerate some, other wise I could put an airstone in there somewhere. This I plan to do once the system is fully cycled. I will need the system to be able to run with minimum maintenance for long periods, that is apart from feeding fish and topping up with water.

Please feel free to pull it apart, I really need the advice and recommendations.

Thanks mate,

Well, first I should note that I'm not an expert and have never built a swirl filter myself, so I'm going off my memory of what I've read here and elsewhere on the internet! The structure you've got drawn there I'd call an RFF, since they've got the inner baffle; swirl filters don't, and all the ones I've seen have been made with cone-bottom tanks though I don't know if that's absolutely necessary.

This paper: http://www.w-m-t.com/library/pdf/Radial ... epaper.pdf (which has been posted here a couple of times previously) found that RFFs are more effective at removing settleable solids than swirl filters. It's a big part of why I decided to build an RFF for my system, and mine definitely works well! I'm going to add a static upflow filter in line after it, to take out the smaller and lighter solid particles; going by what other posters here have said about theirs, they're nice and easy to clean if you build them right too.

In an RFF the inlet should be at least a little below the outlet. If the inlet is above the outlet it'll add turbulence as the water comes up and immediately falls/fountains down, and that will stir things up and make the solids take longer to settle out. Turbulence will aerate your water, yes, but you want that to happen somewhere that isn't inside your RFF, because the gentler the water movement is, the better it works; you make the water movement gentler partly by how you build it (gentle curves in the pipes, for example two 45 degree elbows next to each other are better than one 90 degree elbow, and a longer straight section between the last elbow and the end of the inlet pipe will help the water flow smooth out), partly by increasing dwell time (how long the water spends in the RFF before exiting - this is decided by how fast your water is pumped and how big your filter drum is).

If you want to use bioballs, put them somewhere else. Bioballs work in static upflow filters or moving bed bioreactors etc; Scotty posted about his combination SUF/MBBR here: viewtopic.php?f=8&t=25598&hilit=MBBF+design&start=0#p514569

yep. that is pretty much what people who have used tanks before have done. The 'struts' left help keep the tank sides supported and minimise warping.
(at least those that didn't cut them in half - which often happens with larger tanks)


+1 to what Mel said above re: your drum filters. Scotty and a few others discuss the various types though it does get confusing.....

So what size of solids is the smallest that you want to go to your BF or GB??

Taking into consideration, that the diameter of a Human hair is 80-100 microns?

A 40 micron speck of solids is hard for the human eye to see.

Or the coffee or tea grounds you brew is filtered thru a paper filter down to 10-20 microns.

Thank you for all the comments, I really appreciate the advice and am looking forward to putting it in practice.

Firstly I think I will stick with the current design of the RFF/SF, however I will make sure that the inlet is just below the water level. I will try to keep the flow as smooth as possible by using as few as possible 90 deg elbows and straigt pipes before the filter.

I will plan to add a SUF after the RFF/SF to catch the finer solids. The cleanout of both filters will be used in my soil garden, lawn, etc.

I just want to keep the big solids ending up in the GBs and blocking it up in a few months, I am planning to use pea gravel (sieved river pebbles) as media, anything else, like hydroton, scoria etc. is just not available. I will also try to colonise the GBs with worms.

There is one chap here locally that used charcoal as media in the grow beds. It seems to work but turns the water black for a long time. Not sure if he had any problems with pH, high sulfur, etc. I suppose as long as the plants grow and I can see the fish in my FT and the water quality is good, all is well.

I have read through the attached article on the filters, a very good reference, however it will be a bit tricky to DIY and it sounds like it is designed to be used as a filter system for a fish tank/pond system without the grow beds.

Thank you all again for you advice.