Backyard Aquaponics
A place to discuss aquaponics

David's third system.

I have given brief descriptions of my previous two systems in other, unrelated threads. I figure I should use the right forum area for a description of the latest system.

I have been running this system for over a month, so time to report on progress.

Why I built the new System:
Like Aeon, I am concerned that energy will become more expensive in the coming years, as oil production declines. I want a system that uses very little energy. That means eliminating most of the pumps. To achieve this, I needed to create a gravity fed "trickle aquaponic" system.

The system trickles water to the grow beds until they are damp, then it cuts out. When all the water is consumed by the plants it trickles again. (As a secondary advantage, water consumption has been cut). The trickle amounts to about 1.5% of the total tank capacity per day on hot days - a complete water change every two months. This is not enough to ensure a healthy fish tank, so the trickle system alone is not enough.

For starters - there is no recirculation of water so the issues of ammonia build-up and dissolved oxygen need to be addressed. Solution: A small 12 volt pump circulates water through a biological filter, aerates it, then returns it back to the fish. A 12 volt pump was chosen because Dick Smith have a small, cheap solar panel that produces just enough power to keep it running 24 x 7.

In addition to the trickle-fed hydroponic system, there is a raft hydroponic system. This aids by providing further surface area for microbes (an addition to my biological filter) and the lettuce brings the nitrate load in the water down.

There is a sump at the base of the tank which I hope will help eliminate suspended solids - thus ensuring that my biological filter does not need too much cleaning (so far so good - but it is too early to really know if this works).

The fish tank is 550 litres and runs 23 Silver Perch, a variety of freshwater snails, and 5 yabbies.

As usual, I prefer not to feed the fish with commercial food (I do not want to be dependant on commercial suppliers), so I have a worm farm, an algae pond, and a duckweed pond. These are very small, but adequate. The silver perch eat duckweed, clumps of algae, baby snails, worms, small yabbies, assorted invertebrates (which breed in the algae and duckweed ponds) and any leaves from the raft that trail in the water. They seem to be voracious now that the warm weather is here.

David C.

The system. Like so many of my systems, not pretty - and subject to constant experimentation.

The duckweed pond. It doubles as a yabby holding pond - hence the mesh.

A closer view.

David, I love what you a re trying to do, and it seems to be paying off. Keep up the good work. Does your cheap solar panel charge a battery for night time use?

Yes, it charges a 12v battery - just. Some nights the battery runs completely flat - not good. I may need to go up to the $130 solar panel.

up to the $130 one? How much was the one ya got? I didn't know cheap panels like that existed.

Are you sure it's the panel that's too small. Could it be the battery?

Dick Smith sell a $70 one (or they did two months ago). It barely gives enough charge to the battery to make it through the night.

Is the battery at fault? Maybe. It was old when I started using it here (in its previous life it ran a robot). If it gives me trouble again I will replace it and see if that helps.

I see you bought the bunnings 500L rainwater tank.

I was trying to use one of these as a real rainwater header tank bought from a bunnings in country WA. The sales guy didn't know what the item inside it was for.
That is the stand that you have yours on. At the time I didn't need a stand as the one we were building was 4.5m high and really didn't need it so I had all these plans of using the stand as a grow bed, sturdy, ideal depth, probably food grade etc.

However things didn't work out for that tank as we had to put up a real one.(other people didn't like the look of it)

But this leads onto the topic of solar panels. What wattage is your panel and how many amp hours does your battery store? We installed a relatively small 20w panel to charge a deep cycle truck battery, which was to power a 12 volt pump (6l/min flow) to get water into the header tank 4.5-6m up. It also had to power 2, 12 volt lights and ignite a gas water heater. There is no power/scheme water on this block

This was all purchased from a 12 volt shop (not the cheapest ~ but not much competition if any). I can't remember exact prices but can get them if people are interested.

The pump was only to be run when required so it isn't on all the time.

Like Monya I think you're doing something worthwhile and interesting. Can youo post a picture of the algae pond too? How are you feeding these ponds - are youo trying to keep specific parameters for them separate from the fish water or is it just adding some nutrients to the ponds from time to time?

Hi Aeldric,

I like your approach, too!

The fact is that you don't need to recirculate the water at all if you can maintain appropriate ammonia/nitrite/nitrate levels in your tank.

Water replacement is the means by which you maintain water quality.

I'd suggest that if you're running 23 silver perch you'll probably need plenty of growing space and it will need to be expanded even further as your fish grow.

I'd suggest that your current operation, given the size of your tank, is high risk. You may suffer casualties through the lack of oxygen rather than toxicity.

What you are looking to do is achievable but I'd reduce the number of fish in your existing tank or get a larger tank if you want to run that number of fish.

In previous posts, I've spoken about a Brisbane scientist who did exactly what you're contemplating but she used 4,000 litre tanks which contained up to 20kg of Silver Perch. She pumped the nutrient rich water out of the tank onto her salad greens and Asian vegetables. As she used the water, she replaced it with rainwater.

I'm feeding the algae from an anaerobic digester - kitchen waste. I haven't kept records of how much/often - but it doesn't take much. I guess I feed it about once a month.

The solar panel is tiny - it had a very small rating. From memory 4w. The battery also had a pretty low spec (I don't remember what it was and I am at work, so I can't look it up). I remember thinking at the time that it was pretty marginal. I have a "green water system" so DO can get a bit low at night..... I think I may need to upgrade.

Thanks Gary. I suspect that you are right. I have already told my wife that when the fish get bigger (within months) we may need to double everything - possibly even triple the growbeds. She was not thrilled. Luckily for me, she has saint-like patience.

I am depending on "green water" to help with DO, but this is a risky strategy at night.

Thats great news about the soloar panel - i didnt know there were any cheap ones. Could anyone tell me - if I wanted more power would it make sense to buy several of these $70 solar panels or should I just get one bigger one?
Cheers
Aeon