Backyard Aquaponics
A place to discuss aquaponics

Yes, I too have been “lurking”, and watching, and slowly building my system here in Knysna, South Africa. Here is a summary;

Greenhouse

6m x 3m on a concrete base with all plumbing, electrical and drainage pipes cast in.

Ponds

2 x 1.2M high, 1.7M diameter (approximately 2900L each) mesh ponds.

Sump

2500L water tank

Pump

750W Spec Porpoise. I'm told it can operate 24/7, time will tell.

Grow beds

12 x blue plastic half barrels, flood and drain, siphon loop. I am using a 13mm gravel which is all I can get locally at a reasonable price.

Fish

Tilapia. Oreochromis mossambicus I have about 400 of these in my system average mass of 105g. Not a single fish was lost in transport or after two weeks in the ponds.

Plants

So far I am testing gem squash, strawberries, tomatoes, beans, parsley, origanum, peppers and egg-plant and all seem to be doing well, especially the squash and strawberries.

Water

My current readings, which I know are far from ideal, are as follows;

Dissolved Oxygen : 7 ppm
Ammonia : 0.4 mg/L
Nitrites : 4 mg/L
Nitrates : 10 mg/L
pH : 7.25
Water Temp : 26 – 30 deg C.

Despite these shockers the fish are thriving and the plants are going mad. I am feeding very lightly to keep my Ammonia levels low until the bio-filters are established. And yes, we kick-started with urine. Because of the heat and the sunlight the water is a VERY dark green. I only really see the fish during feeding times. I have been considering UV sterilisers but I suppose this defeats the object of AP. It would be nice to see the fish though.

My first hurdle was to cut a 6m x 6m terrace in the hillside. Massive amounts of clay had to be removed, and I decided pretty early on in the build to lay a concrete slab for my greenhouse to sit on and provide a more stable base. The head from the lowest point in my sump to my fish ponds is about 3m. The ponds have central drains and the water then flows by gravity to 12 half barrels filled with 13mm gravel. Flood and drain with loop siphons to a drain and then down to the sump. I have a another 2500L water tank collecting water off of my roof and we've had plenty of rain lately so I am doing regular water changes (about 2000L at a time) to try and dilute the Nitrites and Ammonia.

I know that my ratios are way out (ie. I don't have enough grow beds but I'll add as many as I can squeeze in.

The system has now been cycling for three weeks. The daytime temperatures here at present are in the high 20's. The greenhouse cooks closer to 40 degrees and water reaches 32 degrees, so I'll be keeping the door open for most of the summer. I had to fetch the fish 400km away and used a 1000L container on a trailer.

We own a reataurant and I would like to feature Tilapia and veggies from our system. I am also considering opening a shop to sell all of the components as their is a groundswell of interest in Sustainable Solutions locally.

My main concerns at this stage;

High Nitrite levels.
Dark green water.
Not enough grow beds.

Any comments or suggestions would be greatly appreciated.

Attached are some images;

good bit of lurking there syn.
Awesome looking system and a great idea of the 'special of the day'.
A ready made market for you...we will be watching!
Good to see the photos.
Merry Christmas to you and your family!

Hi syn, seems like u are all over it, mate. Ur system would appear to be halfway there with reduced ammo and high nitrite. To save u the water change hassle, just stop feeding for a couple days, to let ur bio catch up to the fish load. I know it's hard, but if water is an issue like here in Oz, any saved is a bonus. The fish will live, I promise.
I am finding leafy greens like lettuce are ready 5 weeks from transplanting in my greenhouse. Fruiting plants like zuchs, tommies, bush pumpkin will flower 3 weeks or so after transplant. Don't forget ur iron chelate, (don't spill it on the plants,) and with the fishload things should fly along quickly.
Just keep adding growbeds. I have 400 silver perch fingerlings which don't grow as quick as tilapia and my growth is terrific. Good luck and merry christmas.

wow! what a great system! Welcome SM, great to have you out

For extra growbeds, have you thought about some towers, you could put strawberries or trailing herbs in them. A 1.5m length of 150mm pipe gives you another 25L or so of growbed and they don't take up much space.

Are you running any extra aeration in the fish tanks? You could put some floating rafts in the tank, which would provide some shade and some extra plant matter. You might need to cage the roots though because the Tilapia will munch on them

"Are you running any extra aeration in the fish tanks?"

Yes, I've got a blower to each of the ponds, just in case, (see attachment) Thanks for the idea of the pipes. Might try that inside of the GH. I've been toying with the idea of orchids in pipes suspended from the GH frame.

Great Looking System! I'd love to see more pictures as this evolves!

Talk about lurking with intent..... awesome Synaptoman.....

When you said "mesh ponds" you had me intrigued..... from the photos they are obviously mesh (steel or galvanised??) with a liner insert....

The liner looks pretty thick and heavy duty.... can you tell us what sort it is and it's cost and specs?

Well done mate, bloody bewty

Oh, one thing I meant to mention.... your growbed distribution pipes seem to be a bit above the growbed media... that is if the blue pipes are your distribution grid.... or are they just framing for strength.

I'm wondering if you might be better either dropping the grids down a bit or raising the media level.

Two reasons, reduce evaporation loss due to heat and wind, but more particularly to reduce algael growth on the growbed surface from the splash....

By the way what did you use for your growbed media??

Outer galvanised mesh support, then an inner wall protector made out of UV stabilised plastic sheet, then an inner pond liner. 10-year guarantee (some have lasted 20 years). Price in South Africa about R3000 (A$ 600).



Good point. I was wondering about this. Remind me again. Why do we need to prevent algael growth on the grow media?




It's a 13mm quarried granite gravel. Not great, but all I can get, Attached an image.

Truly amazing! Great work.

The fish would do fine for a week without food while you get on top of the nitrite/ammonia issue. In fact, tilapia are very good at filtering algae from the water. So if you stopped the feed, and shaded the water, I bet a lot of issues would resolve. The algae may also be causing swings in pH through the day, so it would be good to convince the fish to resolve that for you.

Synapto... algae luvs high nutrient levels and will thrive on the top of the growbed if allowed and rob nutrients that the plants would otherwise utilise.

Secondly a film of algae will rob and/or smother the oxygen uptake of the plants lateral roots that spread horizontally from the plants root ball structure.... typically these are close to the surface... i.e just as a soil based plant takes in most of it's oxygen requirement from the lateral roots close to the surface

Keep us posted with your pH levels Synapto.... looks like you're using a "limestone" granite which would tend to pull your pH toward 8.0 +......

The AP system itself will tend to pull pH the other way, so it will be interesting to see how things balance out over time.

salt will detoxify the effect of nitrite. i need to bloody well sticky the ratio somewhere, i've looked it up twice now! anyone remember?

Nice system Synapto... I wouldn't worry too much with about the green water it will clear up as the system matures, plus your Tilapia should be consuming some of it and converting it into flesh..

I took the advise and shaded the one pond and stopped feeding for 5 days. The Tilapia started showing much more interest in the algal scum around the top of the water and I assume they are also feeding lower down but the water is still VERY dark green. The pond with 400 Tilapia is definitely a lighter shade of green than the pond with 50 in. We had heavy rains a few days back and my water tanks were full to overflowing so I decided to do a 2000L water exchange and tested the new water for pH and Nitrites just for interest sake. The readings were;

Nitrites : 0.1
pH :7.00

Why would there be a Nitrite reading in fresh rain water???

My pond readings are now;

Ammonia : 0.4
Nitrite : 4
Nitrate : 25

Ammonia and Nitrites haven't moved even after the shading, no food and a 2000L water change. Strange? My Nitrates are up from 10 to 25. Does this mean that the second stage of my bio-filtration is starting to kick in?

What is iron chelate for and should I be using it and how?

My gem squash flowered within 2-3 weeks of planting. Beans are growing well as are the strawberries. Tomatoes took a long time to sprout from seed but now they seem to be going (I sowed directly into the gravel beds). I have kept them under shade cloth because the sun is fierce and temps around 30 deg. Parsley is also sprouting from seed just as I was about to give up and plant something else. I am watching the mint, celery and rosemary, but all seems well so far.

Attached photos of my tomatoes peeping out, my strawberries that fruited from the day they were transplanted into the gravel, and my squash rain forest.

Thank you all for the help so far.