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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