Aquaponics Garden Part 12 – Turning dead fish into lettuce

A lot of the talk around aquaponics is about how sustainable it is. Locally produced food, sticking it to the man, no gmo’s, and all that crap. Well, don’t get too excited folks. Like pretty much all forms of agriculture, aquaponics requires inputs of fertilizer and energy to produce food. By fertilizer, I mean food for fish and some extra just for plants. This is not different from soil gardening, where, unless you are a diligent humanure practitioner, you also need to bring in fertilizer for the garden or you will eventually deplete the soil. So at some point in your aquaponics journey, you will need to look at your inputs and their sustainability.

My small garden with 8 small goldfish is currently being fed ordinary goldfish pellets, and a homemade gel food. The pellets are made with salmon meal and other ingredients, and the gel has tuna, clams, anchovies, carrot, peas, cilantro, garlic, red pepper, kelp meal, lentils, gelatin and vitamins. The homemade gel food is what goldfish enthusiasts feed their fish. Apparently, if a goldfish is to survive to its purported lifespan, it needs to eat veggies. You’ll notice that salmon and tuna, two high-on-the-food-chain (I know, it’s a web) species of fish with population issues form a large percentage of the diet. So I’m turning endangered carnivores into lettuce. I console myself that if I was simply keeping these fish as pets, the waste would simply be flushed, rather than turning into anything at all, but still, there must be a better way. This issue actually kept me from pursuing aquaponics earlier, but work is being done on this and I’m more confident now that there are solutions.

Fish feed, whether for aquariums or fish farms, is currently made largely from whole purpose caught fish, and byproducts from human food fish processing. The whole fish are mostly those small oily fish that people don’t prefer, like anchovies, capelin, herrings, and sardines. I’m not convinced that these are being sustainably fished, but even if they were, there are never going to be more of these fish produced than there are now, and demand is growing, so alternatives have to be found.  Carassius auratus, (that’s a fancy way of saying goldfish), is actually a filter feeder. In the wild, it swims around the bottom of ponds scooping up plankton and muck, with the occasional egg or bug for dessert. They are most certainly not eating salmon or tuna, or even anchovies. I think there’s a clue here.

William Miller [Public domain], via Wikimedia Commons

 Algae (phytoplankton) and protozoa (zooplankton) are apparently rather easy to grow, as anyone who has had an algae problem in their aquarium or swimming pool can attest. They do not require salmon fillets for nutrition. Any kind of decaying organic matter will feed them, but people also feed them synthetic npk fertilizers. Duckweed is an aquatic plant that is easy to grow and high in protein. It can be grown out from a small sample in nutrient rich water. There we go with the nutrients again. I’m tempted to suggest that a duckweed tank could be incorporated into an aquaponics garden, and it often is, but don’t fool yourself that you could replace any feed inputs that way.

Hermetiaillucens, Black Soldier Fly Larvae: yum!

Bugs are fairly easily (once the appropriate infrastructure is built) grown on food waste, and certainly help close the loop. They are also high in fats and protein and if we ourselves are too fastidious to eat them directly, feeding them to fish and other animals as a replacement for fishmeal makes a lot of sense. Even the most carnivorous of fish can live on insect protein. There are currently some companies pursuing the large scale production of soldier fly larvae from food waste for aquaculture feed, which may make purchasing ready made sustainable fish feed easier in the future. Black soldier flies are native and common to most of the US, but do not exist in the wild in most areas of Canada. I do not live in one of those rare, milder areas of Canada, so I may have to let others raise them for me.

I’ll be continuing to research alternatives to commercial fish feed. There are quite a few people doing work in this area, and it’s encouraging to see that many of the solutions are diy. Of course, commercial feeds are formulated to provide optimum nutrition in a convenient form, and it’s easy to see that diy options may have unintended consequences in terms of the health of the fish and overall system.


Aquaponics Garden Part 11 – Fun with chemistry


When I was a kid, I really, really wanted a chemistry set. One year for Christmas I got an electronics kit that I really tried to like, but it didn’t thrill me. Then I received a geology kit for my birthday. I wasn’t overly interested in the rocks it contained, but there was a serious looking hammer and some test tubes of mysterious liquids that were like a mini chemistry set and were therefore Quite Exciting. They didn’t explode or smoke or anything dramatic when mixed, but I pretended to know what I was doing, and I’m doing it still. Pretending that is. I took chemistry all through high school, and it turns out, it’s not really all that exciting. Or not exciting enough for me to actually remember any of it anyway (in common with the rest of my high school education). But all of that is entirely irrelevant to the issue at hand: high ph in my aquaponics system.

Ph is a measure of acidity or alkalinity. A ph of 7 is considered neutral, while lower values are acidic and higher are alkaline. The scale is logarithmic, so a difference of one on the scale represents a ten-fold increase or decrease in acidity. The water in my system is about 8.3, which is very alkaline. Why this matters is that plants are limited in their ability to absorb nutrients by the ph of their environment. The chart below shows the relative amounts of different nutrients that are absorbed at different ph levels. My water is at the “medium alkaline” level and as you can see this affects phosphorous, iron, boron, copper and zinc.

gl_soil_ph_tableSo what to do? Lowering the ph is difficult and risky, because the fish are going to be negatively affected by any change of more than 0.2 in a day. The carbonates in the water that cause the ph to be high, also buffer the ph so that it remains stable. It is difficult to change the ph by a little – you keep adding acid with no apparent effect, then the ph crashes and fish die. Luckily, the natural nitrifying process actually consumes carbonates, slowly but steadily. What I have begun to do is to treat the top up water with hydrochloric acid (also known as muriatic acid) in a bucket for a day or so before I add it to the system. I drop the ph of the water in the bucket to 6, which consumes carbonates. When I add the water, slowly over the next day, it doesn’t change the ph of the system noticeably but neither does it contribute additional carbonates to the system. This means that the carbonates in the water will actually decrease through nitrification instead of being constantly replenished. It may take some months before my ph is in the perfect range, but it will have happened safely.

In the meantime, I need to be concerned with iron. Fish feed contains some iron, but the fish require it for themselves, and there is very little excess and not enough for plants which are struggling to absorb any at all because of high ph. Many of my plants were showing signs of iron deficiency (yellow leaves) so after consulting the handy internets, I purchased some garden-type chelated iron. I’ll probably need to add a half teaspoon of iron every month or so until I see no more signs of deficiency. I think some aquapons add iron throughout the life of their systems.


Aquaponics Garden Part 10 – I’m gonna eat some worms*


Red wigglers wiggling their way to the dark side.

My latest strange Kijiji adventure involved driving to some guy’s house, giving him some money and receiving a kilo of organic stuff in return. By far, most of the contents of the bag was vermicompost and worm bedding, but buried in there were a hundred or so red wigglers. Compost worms. Worms improve the overall health of the aquaponics system and require no extra feed or attention, so they are well worth the little outing to get them.

Before they can start doing their magic, they have to get from the baggie and into the grow beds, without bringing all their bedding and half-eaten food scraps with them. Thanks to the magic of YouTube, I was able to find a method that worked reasonably well. Just don’t tell the family that I used the salad spinner bowl to do it. Because worms really don’t like bright lights, they will automatically seek out dark spaces by heading down whenever they are exposed. I simply placed a handful of bedding into the strainer and let the worms find their own way into the grow beds. I did end up helping by plucking worms and placing them on the expanded clay media where they soon skedaddled farther down. I expect I won’t see them again until I pull plants out and find them among the roots. Worms can live very well in the media beds, even though they are periodically flooded, because the water is highly oxygenated and the worms breathe through their skin. They will adjust their population to match the amount of food available to them.

So what is it that they do in there? Contrary to popular belief, worms don’t actually consume decomposing vegetable matter as much as consume protozoa that live on decomposing vegetable matter. But this does have the effect of helping to break it down. What this means for an aquaponics media bed is that solid fish waste, uneaten food particles and sloughed off root material will all be broken down by the worms, which will reduce the amount of time I will have to spend cleaning the beds out. While they are doing this, they are also making worm castings – that magical stuff which gardeners wax poetic about. The worm castings are going straight into oxygenated water and being continuously circulated to the plants, which means the plants are being dosed with dilute worm tea at all times. Worm tea is reported to improve plant health by making micronutrients more available to the roots and making the plant more resistant to insects and disease. Apparently worm castings are also dosed with nitrifying bacteria, which, if you’ve been following along, you know are the bacteria that convert fish waste ammonia to nitrates that plants can use.

20140118_122100I’ve been running the system for a month, not long at all, but some of the seeds I planted are starting to look like real plants now. The ph is still too high, which can cause problems, and I’ll talk about what I’m doing about that next time.

*Remember that song: “Nobody loves me, everybody hates me, I’m gonna eat some worms!”? Yeah, I have that stuck in my head now. No actual worms were harmed in the making of this blog.

Aquaponics Garden Part 9 – Growing pains

The aquaponics garden has been running for a little under four weeks now, and I thought I’d give a little update.


In which I pretend I am a mad scientist: today’s water parameter test results.

My water parameters are a bit of a mixed bag. I am very happy to have measurable nitrate (vial on the far right) levels, as this is evidence that nitrifying bacteria have taken up residence in the system, and is also the form of nitrogen that plants are happiest to use. I am also happy to see nitrite (blue) levels at zero, where they are supposed to be. My ammonia levels fluctuate between zero and something barely detectable. Today it is not zero and I suspect that the nitrifying bacteria have not yet become numerous enough to handle the ammonia load of the fish and their feed in as timely a manner as I would like. I must learn to feed less to prevent this. The big glaring issue with the water is the ph. It has been steady at 8.4 since the beginning and this is well above what is ideal for the plants. Goldfish can tolerate ph levels that high, but it intensifies any ammonia problems, so I have to keep a close eye on that. Plants absorb nutrients at different levels depending on ph, and moderately alkaline water can result in deficiencies of micronutrients. The good news on this front is that the nitrification process is naturally acidifying, so over time this should be less of a problem. I live on a huge slab of limestone rock, which contributes a great deal of hardness to our well water. This has the effect of buffering the ph, which complicates efforts to lower it.


Basil plants clearly demonstrating their displeasure.

My poor little basil plants from the grocery store, which were so feeble looking when I planted them, have beefed up quite substantially, but a few days ago, their older leaves turned yellow and black. Obviously this is some sort of deficiency, but the new leaves are reasonably green. Of course, for most of their tenure here, the water has been practically nutrient free, so it remains to see what will happen to them.


Pale seedlings

I planted a lot of seeds, which have germinated marvellously. Planting them involved nothing more than sprinkling seeds over the media and running my hand back and forth across the surface to drop them into the spaces between. Now that most of them are starting to put out their first true leaves, I’m seeing a lot of paleness in the leaves. As the nutrient level of the water improves, I’m hoping the plants will as well.


Floppy Swish Chard seedlings

I started Swiss Chard and a few other things in these little plugs called Rapid Rooters. They are commonly used in hydroponics and promise to provide ideal growing conditions. The chard was doing fine until a couple of days ago when it started falling over. I may pluck one of the plugs out to examine the root system. I fear that chard is sensitive to high ph like its cousin beet, and no doubt the general lack of nutrients has taken a toll.


Extra points for knowing what a troubling is.

The stars of the show are the eight goldfish. They have grown noticeably since arriving and appear to be thriving in their new home. As I mentioned in my last post, I hadn’t really intended to keep them as pets, but they are revealing themselves to be interesting creatures and I’ve really enjoyed watching them.

Now that the system is cycled and the plants have grown up a bit, it’s time to start thinking about the final component – worms.

Aquaponics Garden Part 8 – Won’t someone think of the goldfish?

I have a confession: I have been a goldfish torturer. A serial goldfish torturer, in fact. When my daughter was little, we thought it would be nice to have a little aquarium in her room, so we bought a 10 gallon aquarium and stocked it with 2 fancy goldfish from Walmart. Their names were Toby and Hobby. Toby or Hobby almost immediately perished and was replaced with another Toby or Hobby. I thought we were being amazingly benevolent  fishkeepers to provide a whole 10 gallons of water for two fish, and a while later we added a pleco named Sucker to clean the algae. We had three fish, which, unbeknownst to me, were each capable of growing to eight inches (or actually much, much more in the case of the pleco), in a tiny aquarium with a cheap, small filter and no supplemental air because the air pump made too much noise. Against all odds, those fish lived for seven years, no doubt helped by the negligent aquarium maintenance schedule which probably made for a very good population of nitrifying bacteria (eventually).

My next goldfish mistreatment was when I created a tiny pond in a largish planter outdoors. That arrangement didn’t have any filtration at all, but there were a few plants. The goldfish didn’t survive very long, due to a raccoon massacre which also took out a couple of frogs that had taken up residence.

So this is the thing I didn’t know: goldfish get big and live a long time. Given good conditions, a single-tailed goldfish can grow to 12 inches and live 20 years. They’ll reach most of their full size in three years, but they grow as long as they live. I’m sure everyone has seen large goldfish in outdoor ponds, as I have, but I had also heard that they will only grow to fit the space available. Well, I was stupid and thinking wishfully to believe that. If they are in a small space, they will be stunted, both in growth and lifespan. Their internal organs become crowded and they die.

I read all kinds of advice on stocking rates from an aquaponics perspective, the most conservative of which was one pound of fish per 8 – 10 gallons of water. My system has a 100 gallon fish tank and a 50 gallon sump, but I use 120 gallons as a rough figure for total water since the water does not reach the top of either tank.  I still haven’t figured out how much a full grown goldfish weighs, but I’m guessing it’s a pound more or less. According to these guidelines, my system would have 12-15 fish, though they wouldn’t “fill” the system until they were full grown in 3 years or so. My fish tank doesn’t hold all the system water, as I have a sump tank, so just to make sure everyone had enough space, I was leaning towards 12 (and I have mentioned 12 as the target population). One very popular aquaponics book has a chart showing the ultimate size of various fish varieties. It claims that goldfish reach four inches in three years, which would suggest that many more goldfish than 12 could successfully be kept.

I was curious about the weight and while I was googling on the subject, came across several sites dedicated to goldfish care. Other than mention of record setting goldfish, there was no mention about the ultimate weight of a goldfish there either, but there were recommendations for stocking them. The most conservative figure I came across was one goldfish per 55 gallons of water, in which case I could hold 2 adult fish in my setup. Other advice was to allow 40 gallons for the first fish and 12 for each additional one. Using those guidelines, I have water to hold almost 7 adult fish. My tank is four feet long,  which is the minimum recommended for swimming room. I think where my system is better than most aquariums is in the huge amount of filtration in the form of the grow beds. They provide a massive amount of mechanical and biological filtration, better than even the largest aquarium models. I believe there is also a lot of oxygen in the water, due to the continuous water movement and airstones.

I’m comfortable with the eight youngsters I have in the tank now, and I think they will be fine to grow  to their maximum size. Of course, I will be monitoring the water conditions, and if I am unable to keep the water in excellent condition, I am prepared to rehome some. Although I had thought that 12 would work, I’m now thinking that eight will do. It will take some time before the nutrient level of the water is optimum for plant growth, but these fish should grow reasonably rapidly over the next several months.

I do want the goldfish in my care to have good lives. There seems to be a tendency for aquapons to regard goldfish as throwaways because they are cheap.  I see many examples of aquaponic people keeping five or six goldfish in a ten gallon aquarium. I expect an aquaponics system can hold slightly more than a typical aquarium, but I’m sure that keeping goldfish in conditions under which they struggle to stay alive does not make for a healthy system.  Surely, it’s better to have the nutrients from a few, healthy mature individuals, rather than a bunch of sickly or stunted ones. I’m coming to see them as something more like chickens, those other creatures that no one gives any thought to, but who once you observe and interact with them, you see they are all individuals. I wasn’t really thinking when I started this project that I would be taking on eight more pets, and they mostly don’t have names, but I’m starting to be very protective of my little troubling (that’s the name for a group of goldfish).

Source: The Goldfish Garden

Don’t do this!!!

Some people are starting to sell these mini aquaponics kits, that use goldfish bowls or three gallon betta tanks. Please do not buy one. There is no way for a goldfish to live a good life in a bowl like that. There may be filtration, but the surface area of the water is completely inadequate for oxygen, and there is no room for a fish to swim or grow. It will live a miserable stunted life and then die. It may take a few months, but a fancy goldfish should live for years. The betta tanks are little better, if minimally adequate for a betta fish, which can take oxygen from the air. The main problem with them is the lack of a heater, which condemns the poor betta to a chillier life than is optimum, given their tropical origins. Ideally, they would have at least five gallons of heated water to live in.