Nine month update: the fish


Brutus, approximately 1 year old


The fish at approximately 6 months old.

The most notable thing about the fish since you last saw them is that they have grown 10 times their original size. They were in the 10-15g range shortly after I got them, at I’m guessing 3 months old, and they are 90 – 130g now. What seemed like a ridiculously under stocked tank a few months ago, seems well filled now. If you are considering a small aquaponics system with “just a few” goldfish, please have a look at Brutus in the top picture and imagine how he’d enjoy being crammed into a small aquarium (or worse, a bowl, but don’t get me started). My tank is 100 gallons, with roughly 150 gallons of water in the entire system. There are 11 fish in total. Goldfish will grow fairly rapidly until they are about 3 years old, but they do grow throughout their lifespan, which can be up to 20 years. Yes, you can stock an aquaponics system more densely than an ordinary aquarium, but fish still need room to grow and swim.

20140803_152857I’ve changed the diet back from the homemade gel food I blogged about earlier, to a premium pellet for a couple of reasons. The first is that I’ve been sick the last couple of months and I just haven’t had the energy to make the gel, especially since as the fish grew they were eating much more of it. The second is that I’ve found a really good Canadian fish food, Northfin, that contains relatively low-on-the-food-chain ingredients like krill, herring and sardines and no crap fillers. I picked up a small package at the fish store to try it out, and the fish seemed to enjoy it, but at $10 per 100g it was outrageously expensive. I was able to order a 2.5kg bag online for $80, which is still pretty dear, but should last a good while. These are well-fed fish, in both quality and quantity, and I’m sure that that, along with good water quality, explains their impressive growth.

The goldfish gourmet


goldfish gel food

This is what’s for dinner, if you’re a goldfish.

I made up a batch of gel food for the goldfish today. This isn’t exactly a typical goldfish diet, but it’s what some fancy goldfish breeders feed their fish. My fish have more than doubled in size in the last 3 months eating this stuff and they obviously love it. Goldfish often have problems with their swim bladders and end up unable to swim properly. The solution to that is dietary fibre and lots of folks give their goldies peas that they’ve carefully peeled. This recipe includes the peas, and no peeling required. It’s got lots of protein, fibre, vitamins, colour enhancers, and micronutrients. I include a scoop of commercial goldfish pellets just in case I’m missing something. I use gelatin, but you could use agar agar if it’s available. I use sardines and clams for the protein component because, unlike tuna say, they do not accumulate a lot of toxins in their bodies.

Here’s the recipe:

  • 1 can whole baby clams, drained
  • 1 can whole sardines, packed in water, no salt added, drained
  • 1 red pepper
  • 2 small carrots
  • 1 bunch cilantro
  • 1 cup peas
  • 2 cloves garlic
  • 3/4 cup dry lentils
  • 2 cups water
  • 1/4 cup kelp meal (I buy a huge bag from the feed store and feed it to the chickens and garden)
  • 1/2 cup sinking goldfish pellets (optional)
  • 4 packages plain gelatin

1. Put all ingredients except kelp, pellets and gelatin in a pot and bring to a boil. Cover and cook on low for 45 minutes.

2. Remove from heat and add kelp meal and goldfish pellets.

3. Blend with a hand blender until smooth.

4. Bloom the gelatin: Put gelatin in a bowl and add 1 cup boiling water. Whisk until thoroughly blended. Let sit for 5 minutes.

5. Combine gelatin mix with cooked food mixture.

6. Spread on a cookie sheet lined with plastic wrap and let sit for 15 minutes.

7. Cool in refrigerator for several hours or until set.

8. Cut in 1/2″ squares and place in freezer containers. Store in freezer.

Every morning, I take the day’s portion of gel food out of the freezer and put it in a little bowl. It takes only a short time to thaw, at which point I start feeding the gang a cube at a time several times throughout the day. I squish the cube in the water and they all grab a bit, then go chew on it for a while. Whatever’s left gets hoovered up pretty quickly and I never see any on the tank bottom after a minute or so.

This food is pretty high in protein, and so is suitable for younger fish who are still growing. If you have older fish (over 3 years) you could use a smaller amount of seafood, say, just the clams or just the sardines.

This recipe is based on one posted by the folks at East Coast Ranchu.


How I stopped worrying and learned to love the mulm

20140317_110405This lovely photo is a rare look inside my sump tank. The reason I don’t normally show it is because it isn’t pretty. The fish tank drains into the sump by means of a solids lift overflow. This is a fancy name for a pipe that sucks from the bottom. As a result, the sump has got this brown gook on the bottom that looks very much like what you’d think. It’s mulm. Mulm is solid waste material such as plant parts, fish poo and leftover food in various stages of decomposition. Some of it gets pumped into the grow beds, but mostly it just lurks on the bottom of the tank. But wait, I can hear you cry, this is an aquaponics system – aren’t the plants supposed to clean all that up? Well, yes, sort of, but, as with most things biological – it’s complicated. I’ve posted previously about the nitrogen cycle and it’s a huge part of the process of converting fish waste to plant food, but it isn’t the whole story.

Nitrifying bacteria are delicate, slow growing chemoautotrophs which oxidize inorganic chemicals (ammonia and nitrite) to obtain their energy. The vast majority of bacteria species are heterotrophic and use organic compounds like proteins and sugars to fuel themselves. These guys are everywhere, as anyone who has ever found a sandwich from last year in a backpack on the first day of school knows very well (just me?). So the slightly more correct version of the aquaponic story is that fish eat food and excrete ammonia and poo, and heterotrophic bacteria break down the poo into organic and inorganic components such as ammonia, which feeds the nitrifying bacteria. Bacteria also feed on uneaten fish food, dead plant matter, dead algae, dead worms, dead protozoa and other dead bacteria. It’s a bacteria eat bacteria world in there.

Mulm builds up because larger solid particles take longer to break down than small ones. Eventually, it becomes mineralized. Mineralization is the decomposition of organic matter into its component inorganic parts. Some elements, such as copper, iron, manganese and zinc will not be available to plants until mulm is broken down, because they are only excreted in solid waste by fish. Mulm is also a generous source of calcium and phosphorous.

Another result of the decomposition of mulm is humic substances. These are somewhat mysterious molecules that give a yellowish or brownish cast to natural waters and are negatively charged. This negative charge binds with certain micronutrients and keeps them in solution and available to plants. They also prevent some metal toxicity in fish and plants.

Most of the preceding information I gleaned from an amazing book called Ecology of the Planted Aquarium, A Practical Manual and Scientific Treatise for the Home Aquarist by Diana Walstad. I’d recommend you find a copy, or google the author’s name and read her stuff online, because she has a fantastic understanding of aquatic ecosystems. In aquaponics, we are trying to create an ecosystem with terrestrial not aquatic plants, but much of her information is applicable.

Some folks filter out all solids, while others have a much more laid back approach. Systems using deep water culture, or floating raft methods need to filter. Red wiggler worms  help to minimize clogging by solids in media beds. I am of the opinion that letting bacteria do their job to extract all the nutrition from organic matter is beneficial to the plants and the whole system even if it looks a bit messy in the sump tank. No doubt if I was running a commercial system with high fish stocking rates I’d have a different position, but for me, for now, mulm happens.

Week 12 Update

Mesclun mix, cut and come again many times



Rapini seedlings


Romaine, cut and regrown a couple of times already


Swiss chard, not floppy anymore


Munchkin brocolli, though I wish it was smaller

Things are growing in the basement! Almost everything is considerably more robust since the last update not quite 4 weeks ago, including the fish. I am feeding more than twice as much as I used to, yet the nitrate levels in the system are barely above zero, if they are at all. Today Madeleine brought home a couple of Shubunkin goldfish with pretty calico colours to add to the troubling (everyone knows that a troubling is a group of goldfish, right?). Shubunkins are single-tailed hardy goldfish with fancy colours, but not the strange body shapes that most fancies have. Hopefully they will help add nutrients to the system.

We’re eating great salads several times a week and I’m reseeding regularly to keep the greens coming. I add iron to the system every three weeks, as iron deficiency is a common problem in aquaponics systems in general, and particularly in systems with high ph. My ph is still high (8.0 – 8.2), but the carbonate level is gradually coming down due to nitrification. I add 15 litres of water to the system every five days or so, to replace water lost to evaporation and transpiration. Unfortunately, when water leaves the system that way, it leaves its carbonates behind, so I make sure to treat the top up water with acid a day before I add it, which has the effect of consuming all the carbonates. This way the carbonates in the system do not increase over time. Given the good growth of my plants, and the fact that fish and nitrifying bacteria are fine with the higher ph level, I am not making any other effort to reduce the ph, and I am taking it on faith that as the system matures, the ph will drop naturally. Then I will be happy to have such hard tap water to add to the system to replenish carbonates.

I’m still very excited about my aquaponic garden, and I’m looking forward to the even greater productivity that will come in a few months once the ecosystem is fully established.

First greenhouse thoughts

Too much?

Too much?

In my climate, to run an aquaponic greenhouse is to run a heated greenhouse. I can’t do an Eliot Coleman style hoop house with row covers and simply wait out any cold spells. If I am to keep water running through the aquaponics set up, I have to keep the temperature inside at least a couple of degrees above freezing. Even if it’s in the minus crazies outside. I’m a little nervous about that, actually, because if I failed at that, and things froze up, I’d lose more than a few plants. Ice and plumbing just don’t play well together. It’s not just heating though – there are thermal mass and insulation to think about as well.

Another thing to consider is that at very low temperatures, nothing grows very well. Fish metabolism slows to almost nothing, nitrifying bacteria take a vacation, and plants just kind of stay alive, rather than grow. This means that unless I do a lot of heating, and lighting for that matter, I won’t get the same kind of crops from my outdoor aquaponics over the winter as I do in my climate controlled basement setup. So why would I want to move outside anyway?

Moving outside would allow me to expand my aquaponics garden. It would allow me to take advantage of the free sunlight, especially in the spring and summer when growth is most vigorous. It would give me a place to go in the winter to escape the cold and snow. I would hope that whatever heating is required for the winter months would be offset by the reduction in lighting that is necessary 365 days a year in my basement. I think there are calculators online that could help me figure that out.

I’d love to have a large greenhouse where I could set up a huge aquaponics system to grow most of my family’s vegetables for the year. I’d need to have a large heating plant, and quite frankly, if I’m honest, it isn’t necessary. I will still have my main outdoor garden where I can grow lots of storage vegetables and I will mainly grow herbs, greens and salad plants and some extended season tomatoes in the greenhouse. If I keep the greenhouse small, I can keep the heating requirement small as well. I’m leaning towards vertical grow towers to maximize light and space.

Here are some greenhouses that I find inspiring:

Week 8 update

Indoor aquaponic garden

Indoor aquaponic garden

Eight weeks ago, I decided that everything worked and nothing leaked and it was finally time to start growing fish and veggies. I powered up the pump and it has been running ever since. Shortly after, I planted a few plants and a lot of seeds, and shortly after that I installed the goldfish. My system was cycled almost immediately, thanks to a donation of used filter floss from my daughter’s mature aquariums.

As far as the plants go, I’m happy to report that the initial spindly and anemic growth has been replaced by much more robust growth. We’ve been eating salad greens for a few weeks now, and the rapini was wonderful. I never manage to catch rapini at the right time when I grow it outdoors, but this bunch was perfect, and no flea beatle damage! I keep planting seeds to have a continuous harvest.


The “poopies” eat out of my hand.

The goldfish appear to be doing well. They are growing and their colour is nice and bright. Their water is clear, and more importantly, the ammonia and nitrite levels are consistently zero, and the nitrate levels are very low. This means that almost all of the waste is being processed by the system and used by the plants. One of the original fish died, and I replaced him with three more, giving me a total of 10 fish. I’ve been feeding them generously to make sure the plants have enough nitrogen. The fish don’t mind.

I still test my water parameters daily, which may be a bit over the top at this stage, but since the system really runs itself aside from me adding feed, I like to do something. I’ve been recording the water values and anything else I do to the system in a paper notebook, and also in a diary on a site called This is an Australian university research project on aquaponics systems that anyone can participate in. The idea is that many people will add their data and everyone has access to information from other systems. So far there aren’t that many people participating, but the diary displays data in table and graph form, so it’s an interesting way to monitor changes over time.

I’m still very excited about the aquaponics project. I haven’t had any horrible disasters and everything works much the way I anticipated it would. As a proof of concept, I’m declaring this project a success. I’m already thinking about expanding and moving into a greenhouse, but I would miss the constant water sounds from the basement. Maybe I’ll just have to build another system outside, instead of moving this one.

Weighing the options

A chubby goldfish

A chubby goldfish

After getting the aquaponics system all set up in the basement, I had no appetite for spending any more money on this project. One thing I did buy, and I’m very glad I did, is a digital scale. If you are doing aquaponics or thinking of it, I recommend you do, too. My scale was only 15 bucks, but it does everything I need: it holds up to five kilograms, it has one gram accuracy, and it has a tare function, meaning you can zero the weight of the container.

The thing that prompted me to buy the scale, was the issue of how much to feed my fish. I don’t have very many fish, and I want to maximize their ammonia outputs without over feeding them. Young fish can be fed 2 – 3% of their body weight per day, but I had no idea how much that was. So I weighed my fish. It turns out that my fish were about 12 grams each, times 8 equals 96 grams of fish. So I can feed them 2 – 3 grams of dry food per day. My next problem was that I feed a frozen gel food in addition to pellets, and I needed to find out what percentage of the gel, by weight, is food and what is water. I weighed out some gel food and microwaved it until it was hard, then weighed it again. It turns out to be about 20% dry food, so now I can figure out how much to feed. I usually feed about 8 grams of gel and 1 gram of pellets per day, about 2.5 grams of dry food equivalent.
20140113_202234In another post, I mentioned that I add iron to the water to prevent iron deficiency in the plants. The recommended rate is 2 mg of pure iron per litre of system water, every 3 weeks, which in my system comes to 14 grams of 7% chelated iron. I don’t know about you, but I’m not very good at eyeballing powdered iron, and the scale takes all the guesswork out of it.

Today's rapini harvest

Today’s rapini harvest

I’ve also been weighing my harvests. I keep a system journal with all the water parameters and everything I do or add to the system. Knowing how much is coming out of the system is just as important as knowing how much went in.

So if you are making a list of required equipment for your aquaponic project, don’t forget the digital scale!

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.

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.


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.