Brisbane Local Food

Growing local

Finished setting up my new aquaponic pond!  Well, I say finished... but are these sorts of things ever truly finished? I’ve been tinkering a lot over the last few weeks, so who knows what my next hare-brained scheme for it will be. But, I have reached the point where the only further plans I currently have in mind for it is to add more fish as the system cycles up to be able to handle their waste and trim the dracaena to give it a bit more sun as it establishes.

I’ve been wanting an ornamental pond for some time to attract wildlife to the garden as well as grow a few moist bits and pieces like waterlily, water chestnuts, pickerel rush, watercress and azolla—and adding an aquaponic growbed as a filter only made sense. I love the concept of the closed loop system where each part of the system provides for the needs of the other with minimal input from me. With the plants taking the fish waste from the water, it also means I can stock many more fish in the pond than I would otherwise be able to maintain, as well as experiment with a cool and different way of growing things.  Most aquaponic systems raise edible fish to get another yield out of the system, but I’m not particularly fond of fish as a menu item, and I’d probably want a larger system than I was planning on at this point anyway, so for now I’ve just got a couple of goldfish and some little mosquito-eaters in there. I know, the goldfish will probably eat any frogspawn we're lucky enough to get, but as I said the primary purpose of the pond is ornamental, so I'll cross that bridge of maybe using gutterguard to fence off a frog-preferred bit of the pond when we come to it.

My five year old son is incredibly excited about the fish, and it’s his job to feed them. He particularly likes giving them their quarter of cooked zucchini in the morning (we started giving them this because otherwise they spend the day between feeds browsing on the establishing waterlily’s new baby pads, which you can barely see among the azolla for now.) They love zucchini though, and by the following morning they’ll have eaten every last scrap of it. And my son loves giving it to them because they’re so keen for it that they “kiss” his hands while he’s putting it in.

The pond is hopefully far enough above ground to deter cane toads—if it’s not I’ll have to plant some thick shrubbery around the uphill side. Maybe blue flax lily, I’ve been looking for a spot for that. In the pond, I used a surplus stepping stone to weigh down an upturned plastic pot with hole cut out to make an underwater cave, making an easy spot for animals to climb out if necessary as well as some underwater hiding places for the fish. Positioning it under the water outlet from the grow-bed makes it sound more like a gentle gurgle and less like a forgotten tap running. And the fish are hilariously excited about this setup! When the growbed’s draining, they get up in the shallow water on top of the stepping stone and swim furiously against the current, like they're on the fishy equivalent of a hamster wheel. XD I think they particularly like it because it's not available all the time: only when the bed's draining and only when there's relatively more water in the system, because they get bored after a while and stop even when they could, but then go back to it after the water level's sunk and then I've topped up the system. An upturned broken pot with some rocks inside and a laughing Buddha gifted to us by an old friend complete the setup to make a moist hidey-hole that I’m hoping will provide an inviting shelter for local frogs.

I used the bottom section of a broken old worm farm as a grow bed (I’ve never been good at worms; thank goodness I’ve discovered that soldier flies can live with me). I fitted in a standpipe out of irrigation odds and ends and fitted some gutter guard wrapped around a plastic pot to keep the grow media out of it, then used an old baby food jar to make a bell siphon, which works amazingly well to turn the constant trickle of the pump into a flood and drain system for the grow bed. I may have punched the air when it worked first time. Physics is awesome. I fitted some scavenged old bits of downpipe spruced up with a bit of leftover paint as a strawberry tower, as research suggests they prefer having water trickle past them rather than flood and drain. 

Leafy greens tend to grow the best in this kind of nitrogen-rich system, so in addition to the strawberries, I’ve packed in some iceberg lettuce, some kale, a few flowers, and in a fit of enthusiasm planted corn at the top of the tower. I planted a couple of different plants in each location to see what does best where, so I guess we’ll see! Everything is deliberately packed in there—apparently aquaponic crops don’t need to fight for below-ground resources, so the only limiting factor is sun, which can sometimes be too much of a good thing over summer! In any case, I can see what works best and thin accordingly as necessary. Fingers crossed my fruiting crops work.

I’ve attached a solar pump to the whole thing that I bought off ebay, and it goes whenever the sun shines. It’s a no-no in aquaponics for the pump to stop, ever, but I think I’ve made it work. I punched a small hole near the bottom of the standpipe so that if the pump stops when the bed is nearly full but hasn’t yet activated the siphon, it will slowly drain down to about the level of a self-watering pot. Once the plants are fully established, at least the ones in the bed will probably get their roots right down to the bottom which always has a bit of water in it. The fired clay pebbles I’m using as a substrate in the grow bed are porous so they stay moist enough during the night & on cloudy days that I haven’t had any problems with the plants wilting for lack of moisture—and on the hot days when they need lots of water, the pump will be operating at its best.

Speaking of which, I thought I had to have a leak last week, despite having felt around the outsides to find the ground was bone dry. A bit more research suggests it’s quite common with an aquaponic system to think there must be a leak, when really it’s the plants drinking the water causing the level to go down. They drink a LOT, so I guess that makes a second input into the loop: fish food and water. Still, it’ll only lose the water the plants actually use (plus some evaporation from the surface of the pond where it’s not covered in azolla), so I consider it a win. Maybe I have a leak a well, but I'm going to observe and measure a bit longer before I freak out and drain the pond looking for it.

In any case, the solar pump does have a battery which it charges while operating in solar mode. I expected when I bought it that it would automatically switch over to the battery and run as long as it could, but apparently that was too sensible for it. I can activate that battery manually if I think things are getting a bit dry, or when I’ve put in some new plants that need some TLC. It only lasts for a couple of hours, but the solar by itself seems to be doing the trick for now, so fingers crossed it’ll be good enough. I’ve ordered a solar/battery air stone which is advertised to automatically failover from solar to battery and last through the night (like I had assumed my solar pump would do) to keep the dissolved oxygen in the water up once there’s more fish in there, as before I got the pump running the fish were starting to gasp a bit in a still pond even at my light stocking levels.

The other issue with the solar pump is that it varies in speed according to the time of day. When it's just getting started in the morning, it fills up the bed but not fast enough to activate the siphon to drain it. When it's high noon, it fills up the bed so fast that the siphon never breaks, so the bed hovers at around half full. But it seems to be good enough, and since I've got the water trickling down the strawberry towers I don't have to worry too much about drowning my aerobic bacteria if the bed stays full for a few hours--and I can always move to a more expensive (in dollars or DIY custom build labour) system down the track when I've got a bit more experience.

I’m trying to monitor my water quality for the things that should happen as the system cycles up and the bacteria get established in the growbed substrate. I should get a spike in ammonia, then one in nitrites, then in nitrates. But very little is happening with the levels; they’re all stable at zero or pretty close to it. I’m wondering if I’ve been too conservative in my initial fish stocking level, or if the system’s already been cycled up by the gradually-gradually process of tinkering bits and pieces into place as I had time, and so by the time I got around to starting testing the bacteria were already munching through the fish waste and my plants were sucking down the available nitrates. And today I tried confirming the pH—I’ve got a seachem monitor in the pond that’s reading 7, but I’m not sure I trust it. But the aquarium easy test strip reported 8.4. Aaaargh! Surely my strawberries shouldn’t be looking so lush if the ph is that high? Then I found some other ph test strips I had left over from years ago and they measured 5.3, which means my fish are already dead. (They’re not.) None of which gives me confidence in the quality of any of the tests I have, and so I have no idea which if any of the measurements I’m taking I should trust. Oh well, I'll just trust nature to balance it all out in time unless I notice something looking unhealthy.

So basically, the whole thing is a great big we-shall-see. In the meantime, the plants are looking healthy and growing. And the fish are looking healthy and happy. And I’m having lots of fun experimenting and solving the problems as they crop up. Everybody wins!

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Comment by Dave Riley on November 23, 2019 at 9:04

Your Azolla got my attention Lilly. So I've ordered a few scoops. There's a useful resource here -- The Azolla Foundation.

Worth a squiz to log  its versatility and speed of growth.  :

Every home should have an Azolla pond or container for the garden soil,for any livestock...maybe for their own menu. Just don't allow it to enter your local catchment as it can sometimes be problematical.

Comment by Andrew Cumberland on November 9, 2019 at 14:33

I often say an aquaponics system isn't really much work - but you do need to be attentive and check it twice a day.  It must have been the week for it Lily.  I had a pump out as well.  Unfortunately, I was away so I lost quite a few plants. Still, the fish were fine and the second grow bed was still running from a second pump so all is well.  Yours is really looking good. 

Comment by Lily on November 9, 2019 at 8:23

Thanks, Susan! I'll have to host a gathering when I'm feeling less shy. :)

It's been an interesting week for the system! On Wednesday, in the strong winds, the solar panel blew off the roof where I'd had it precariously propped up on a brick. I popped it back up on the roof and framed it with a couple more bricks to stop the wind from getting under it. On Thursday night (36 hours later) I noticed my system was looking a little... sad. The water in the pond was murky. Caterpillars had got to all my kale (not exactly a surprise given the season, but still), and the strawberry leaves were looking yellowish and dry. The corn looked worst of all--as a heavy feeder in the driest spot, it was actually a little droopy. Hmmm. Further investigation showed that the bricks I'd used to protect the solar panel were actually shading it, and thus the pump had been non-operational for a day and a half, both days being hot. (Fortunately I discovered this before Friday!!!) I bailed a bit of water from the pond through the grow bed (narrowly avoiding bailing in a couple of sleepy fish who trust me too much XD) to give the plants some instant relief, and rearranged the panel such that it should get all day sun again. Next morning, the pump started running again, the plants immediately drank enough water that the pond level dropped a full inch, and they were happy through Friday's stinker. Close one! I'm pretty pleased with the demonstration of the system's resilience, though, having made it 36 hours without the pump before showing signs of stress, and that being alleviated immediately by reactivating it. It's not a test I would have deliberately run, but it gives me some parameters on how closely I need to monitor it and how long I've got to respond if there's a problem.

In the last few days, I've been noticing my pond being regularly visited by bees, which perch on the azolla for about a minute, drinking, and then fly away again. So glad to have provided a pleasant watering stop-off for our local insect wildlife in this hot weather.  There's often two or three bees on there at a time, the next one buzzing in before the previous one has finished his drink and flown off again. <3

My duckweed seed population has arrived--this time I am breeding it in a separate bucket with some azolla in there as well so that the surface is completely covered, as well as a population in a floating plastic pot in the pond anchored to a rock on the bottom with string (which just means the fish can't get at it, but any mosquito larvae will hopefully drop out through the drainage holes and be eaten by the fish) along with a bit mixed in with the azolla on the main surface of the pond which hasn't yet disappeared. The fish seem less immediately keen on it at this point, possibly because they've got zucchini to browse on all day and aren't so hungry as they were when I first tried adding duckweed. My hope is to phase out zucchini and have them eat the duckweed instead once I've got a stable population of it.

Comment by Susan on November 3, 2019 at 6:59

Wow, this looks amazing.  I would love to see this little small scale aqua pong system in action.  

Comment by Andrew Cumberland on October 31, 2019 at 9:29

My chickens and quail can't get enough of the Azolla either. 

Comment by Lily on October 30, 2019 at 23:21
Thanks, Christa! I’m glad you like the look I settled on. :)

Thanks also, Dave! I’m really chuffed you like the setup. :D The azolla is definitely awesome! Now it’s bred up to cover the surface (shading out the algal bloom I was having earlier), I’ve been harvesting a big double handful of it out of the pond every day for my compost, which seems to be just the right level to keep the cover where I want it. Apparently it forms hummus within a week or two, and I certainly can’t find any of the odd bits I’ve tossed in the garden when they stuck to me. I did try keeping duckweed in there too, but the fish ate it all quicksmart before it got a chance to get established. Apparently they don’t like the azolla though—they nibble it but spit it straight back out again. I need to get a new lot of seed duckweed and protect it a bit better before letting the fish loose on it. I haven’t tried eating the azolla myself as yet—to be honest, I was a bit put off by the fact the fish didn’t like it!
Comment by Dave Riley on October 30, 2019 at 19:17

Azolla is an fascinating plant. Oftentimesseen as  a weed.

However on balance, it is worth a squiz.

When I've grown it, it makes great mulch. But I'm thinking of experimenting with it further primarily because a Azolla mat is not mossie friendly.

You can get Azolla out of most Brisbane lakes or watercourses.

Lily's setup is so inspiring!

Think about the smartness of it all --aside from the Azolla!

Please feature.


  • Azolla covering water surface reduce light penetration of soil surface, resulting in the depreciation in the germination of weeds (70% of the weed). Thus growth of azolla reduces aquatic weeds in flooded rice fields.
  • The integrated use of azolla with rice and fish farming has been developed. The integrated approach can enhance a farmer's income while reduce the use of pesticide and fertilizers and consequently environmental pollution.
  • It can fix atmospheric nitrogen, carry out photosynthesis and uptake nutrients from its surrounding environment through its root system.
  • It has wide range of use including fodder for dairy cattle, pigs, chicken, ducks and fish.
  • Azolla can be used for all type of vegetables and plantation crops.
  • In some village communities it has even increased the overall milk yield.
  • The application of azolla as biofertilizer on agriculture crops, in order to provide a natural source of crucial nutrients nitrogen, can be very beneficial for the future.
  • Due to fact that rice paddy field from an ideal environment for azolla.
  • Improve the nutritional status of the soil.
  • Azolla has been used as green manure.
  • Improve yields by 15-20 per cent.
  • Azolla can be used as an animal feed a human food, a medicine and water purifier.
  • It may also be used for the production of hydrogen fuel the production of biogas the control of mosquitoes and the reduction of ammonia volatilization which accompanies the application of chemical nitrogen fertilizer.[SOURCE]

 

Comment by Christa on October 30, 2019 at 17:13

That's a lovely little pond with the buddha sitting there amongst the azolla, it looks natural and cool.  I am not into aquaponics, but I love ponds surrounded by plants.  Hope it all go to plans Lily.

Comment by Lily on October 29, 2019 at 21:20
Thanks, Andrew! Yes, I decided to go with the solar pump in the end despite advice to the contrary because while it would be great to have the system running day and night, loaded with fish and vegetables both, I’ve been trying not to add anything to my home that can’t be powered renewably, and I couldn’t justify it for a little ornamental pond and a couple of square feet of grow-bed where I could perfectly well use the soil underneath it instead. When the pump breaks (as I understand pumps do with distressing regularity)—or if I decide it definitely won’t work with an off-the-shelf solar pump—or indeed if I decide aquaponics is so productive that I must put it in on a larger-scale—then I can consider which direction to take things from there.

Regarding dissolved oxygen, I absolutely agree. I’ve got an air pump on the way that I’m hoping will successfully operate day and night so the fish don’t suffer for the variability of the system.
Comment by Andrew Cumberland on October 29, 2019 at 19:14

It's looking good Lily.  I would have advised against the solar pump as well - however, if it's working, all good.  My advice would be not to increase the fish load too much, regardless of what the plants are doing.  It's as much about air in the water as ammonia etc. The way you have the water returning to the tank is helping break up the surface tension as well which is good.  

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