While reading about Peak Oil I stumbled across a way of growing large amounts of food in small areas (enough to feed your family in the area of a small back yard). The system is called Aquaponics. The idea is that you have two tanks, a grow bed and a fish tank. The water from the fish tank is pumped over the grow bed, then returns to the fish tank via gravity.

Here is the design for small system from the Backyard Aquaponics site:

The fish are little fertiliser machines. They take food, and output nitrogen rich fertiliser. This gets pumped onto the grow bed where bacteria break down the fish waste into nitrogen compounds. The plants just love these compounds and grow like mad, cleaning the water at the same time. A very neat little system – you get rapid growth of plants and fish. It’s a protein/vegetable machine. With no artificial (i.e. derived from oil) fertilisers. I have seen claims of 50kg of fish and 200kg of vegetables from backyard systems over 6 months, which I figure is enough food to supplement (or feed entirely) a typical family.

Now I am pretty geeky and have never grown a thing in my life. I am much more comfortable with silicon and solder than dirt and water. However aquaponics interests me for a couple of reasons:

  1. If the Peak Oilers are right and transport and hence food costs increase dramatically, then knowing how to grow some of your own food could be a very useful skill to have in a few years.
  2. I am intrigued by the possibility of efficient food production for the developing world.
  3. It has the right sort of complexity to interest me, i.e. I get to mess with pumps, and dream about solar powering the whole thing. I also like the idea of the symbiotic system, lack of waste and efficient use of water.

Inputs are water, a little fish food (I understand you can grow your own worms if you want), sunlight and electricity for the pump. The electricity bit I don’t like. I would love to go solar on this, and work out exactly how much water flow I really need. In a developing world situation is it easy to imagine a hand or bike powered pump, or even in a pinch a bucket.

So I bought an aquaponics DVD and book and decided to have a go. Of course I wanted to go full-throttle on this and build a large system but wifely approval was not forthcoming so I scrounged a small, skunk-works type project for about $75:

  • small 1200 litre/hr 15W pond water pump ($40). Probably too big for what I need.
  • 10 goldfish ($20) (2 have gone to fishy heaven so I have 8 left).
  • 1 tomato and 1 chili plant seedling ($10).
  • old ornamental pond ($0).
  • empty plant pot ($0).
  • gravel from driveway ($0).
  • fish food ($5), half gone after about 10 weeks.

To complicate matters I am a notoriously fussy eater and don’t actually like fruit and vegetables much! So I planted all the stuff I do like to make a pasta sauce: tomatos, chili, and garlic! I would have also liked to plant potatoes and onions but I am not sure if those sort of vegetables work in aquaponics systems.

My goldfish are not for eating (unless you are a neighbourhood cat), just to provide nutrients for free. Here is my system:

This is about 8 weeks after starting. The large plant on the left is the tomato and was just peeking over the top of the pot when I planted it. The pot sits on some bricks in the middle of the pond. A small pump supplies water to a plastic pipe laid on top of the pot with a bunch of holes punched in it. The water trickles down the rocks in the pot to the pond.

Here is a top view:

The pump is under the water at the bottom left, you can see the electricity cable running to it. The fish get all excited when they see me, as they think it’s lunch time. They really do recognise me BTW. It’s nice to be wanted.

Just when I thought I was getting into the groove of this gardening caper I suffered a biological warfare attack. Nope, it wasn’t Saddam, or even Osama, but some caterpillars having a party on my beloved tomato plant:

There was some low level nibbling for a few weeks then in the space of just two days half my bloody leaves were gone! It took me a while to work out the problem, but I bought some spray from the local gardening shop and after a good spray I noticed a big fat green caterpillar wriggling in the water. Apparently they can’t swim. Too bad.

I also noticed some of the little yellow tomato flowers dropping into the water. This is bad news as it’s these flowers that turn into tomatos. A bit of Googling showed that this can happen when tomatos get too much nitrogen. Now it just so happened that I had started feeding the fishies twice a day, as I had thought the now-larger plants would need more nutrients. So I have now backed off to just one feed a day and the latest crop of little flowers are staying put.

Some relatives who know something about gardening have also suggested I prune the tomato plant, this focuses growth on the tomatos rather than unnecessary branches.

Some lessons learned:

  • If the pump gets blocked, you can get into big trouble quickly, e.g. my tomato plant went all droopy within hours. If you have a high stocking density of fish I understand their oxygen levels could also drop quickly which could lead to disaster.
  • The pond water is crystal clear; my experience with fish ponds is they usually go quite green. So the systems seems to be cleaning the water quite nicely.
  • A large scale system could be made really cheaply. The two tanks could be holes in the ground (one slightly above the other to provide gravity return) with cement or plastic lining. Fish breed for free. The rest is labour.

Aquaponics uses small amounts of water compared to regular agriculture. I use about 1-2 buckets a week (4-8l), not much compared to what I imagine would be regular watering of these plants if they were planted in soil. When you think about it, normal watering of crops is grossly inefficient. When you spray the water around you maximise it’s surface area, almost guaranteeing most of it evaporates before it can get to the plant.

You see I live in the state of South Australia, which is the driest state in the one of the driest countries in the world. We also have serious water supply problems, persistent droughts, and the climate change is making that much worse. So low water consumption is a very good thing.

It’s kinda cool to see the growth in action, little flowers turn into baby tomatoes and I have countless green chilis. The garlic plants spang from single cloves that I just pushed a few cm under the rocks, it was amazing to see little green shoots emerge a few days later! I also enjoy messing with the system every day, it gets me out of the home office and into the back yard. I would really like to build a larger system, with say 20 eating-fish, and a solar powered pump system. However my wife is afraid we won’t eat all the food it produces. Maybe a project for 2008.


Backyard Aquaponics


I recently had to restore this blog from a backup and unfortunately lost the two comments from the original version of this post.

Floatron for a Low Energy Pool

I recently did an energy audit of my house and discovered that my pool was a major energy hog. Due to the salt chlorination system we need to run the filter/chlorinator for between 2 and 10 hours a day to maintain high chlorine levels. We run it longer in summer as the chlorine gets removed by sunlight (even with stabiliser chemicals).

We use a salt-chlorinated system (common in Australia) where about 20A at 12V is passed through a special salt cell that causes chlorine gas to be made from the slightly-salty pool water. You dump a few 25kg bags of pool salt into the pool every year to provide the chlorine ions, the salt cell adds electrons to make dissolved chlorine. If you keep the chlorine levels high enough, it kills the algae that would other wise make your pool bright green after about a week.

I attached my power meter to the pump/chlorinator and measured 860W (200W for the chlorinator cell, 660W for the filter pump). Based on an average run-time of 6 hours/day that’s over 5 kW-hrs a day or around $300/year at my current tariffs. Added to this is a new salt-cell every 3 years (at $300 each) plus a legion of algicides, stabilisers, and other exotic potions from the pool shop. All up I would estimate around $700/year, plus maybe $150 for every “green pool event” which occurs if (well, when, actually) we are not diligent.

But it’s the 5kW-hrs a day that really bugs me. You see I want to install a PV solar array for my house that will generate perhaps 9 kW-hr/day total. No way I want to use a good chunk of that power on a pool we hardly use. That sort of energy waste is just so 20th century! To be honest I would be happy to cover the top of the pool and turn it into a 60,000 litre rainwater tank, but on a good day it does look kinda nice:

So I started looking around for alternatives to chlorine. Some Googling brought me to the Floatron. This gadget uses a completely different principle to zap algae – ionisation. Rather than using chlorine it injects small amounts of copper ions into the water, which apparently kills algae but doesn’t bother us much. The cool thing is that copper ions last for 3 weeks, regardless of how hot it is. This also means that the copper ionisation process can be solar powered, as just a minute amount of electricity is required.

The testimonials looked good, so I tracked down the Australian distributor and bought one. It wasn’t cheap, about $450 delivered. There was much “wailing a gnashing of teeth” over the price by my wife, sick of spending money on that (add choice Italian swear word) POOL, but I convinced her that if it worked it would pay for itself quickly. I was a little bit nervous about the purchase, I mean, if it’s that good why can’t I buy one in my pool shop? More on that question later.

So I threw it in the pool about 2 months ago and duly followed the instructions. As the copper levels built up I reduced the chlorine by lowering the time we ran the pool filter/chlorinator each day. So far so good, the pool is healthy and my energy use is way down. After 2 months I now feel I know how to manage the pool using the Floatrons ionisation method.

With the Floatron you still need trace amounts of chlorine (about 20% of what is normally required). As well as killing algae chlorine also acts to keep the water clear. Initially, in my rush to reduce energy consumption I reduced the filter/chlorinator run time to just 1 hour a day. However the pool water tended to be a little blue-green and cloudy (e.g. objects on the bottom of the deep end were fuzzy). Any sort of green in normally a sign of algae breeding madly, so there was a moment of panic!

However I think it was more a case of dissolved (but benign) particles in the water rather than a run-away algae event. I upped the filter/chlorinator run time to 2 hours a day and after about 3 days: clear blue water, about as good as I have ever seen our pool. The chlorine level was still very low (maybe 0.3ppm, way lower than 1.5ppm required normally), but the water was clear. Normally at this time of year (November) we would be running the filter/chlorinator 6-8 hours/day.

Now this management of the residual chlorine level gives me an added level of control. I could drop back to 1 hr/day on the pump if I wanted to. I would get cloudy water but who cares if I am not using it? No risk of an algae attack so I can rest easy. Then, if we have an imminent party or kid invasion coming up, I just up the run time to 2 hours a day to get clear water. I like having this choice – previously I was forced to keep the run time (and expense) up, waste power and effort, as if my pool ever went green it would take me 2 weeks and $150 of algicide/shock treatment to fix it.

This got me thinking about the whole salt chlorination system and business model, and the reasons why using ionisation (rather than chlorination) isn’t that common. I mean the Floatron has been around for 15 years, so why aren’t we all using it?

Think about a salt chlorinated pool. If something goes wrong, e.g. the salt cell gets blocked or you flick a switch the wrong way and you don’t notice for a few days you get a green pool quickly, as the chlorine level drops immediately, especially in hot weather.

The warmer it gets, the more quickly the the chlorine breaks down, so the more you need to run your pump/filter/chlorinator. We varied between between 3 and 10 hours/day over the year, more in summer if the chlorine levels were low, or if the salt cell was nearing the end of its life. Plus you have the expense of a $300 salt cell every few years (we have gone through 2 in 7 years). Being chemically-challenged and slightly lazy we always end up with 1 or 2 “green pool” events a year. This means a trip down to the pool shop, $150 worth of shock treatments, algicides, and much stress and head scratching while we work out what we did wrong this time.

There are other benefits apart from reduced energy costs. Running the filter and chlorinator for a only a few hours a day reduces lots of wear and tear on expensive equipment, perhaps as much as 80%. Using ionisation to kill bugs means less risk of the pool quickly spinning out of control and going green as the copper ions last 3 weeks compared to chlorine in summer that lasts just a few hours. Now all we really need to buy is a few litres of acid a month to keep the PH between 7.2 and 7.8.

So the Floatron is a great thing for a pool owner but a very bad thing for a Pool Shop owner. Just about every dollar we spend at the pool shop is related to chlorine in some way, for example pool salt, algicide, new salt-cell, stabiliser. It even saves on filter sand and kreepy-krawly (automatic pool vacuum) replacement parts as they wear in proportion to filter use. This works against the Floatron – what pool shop would stock a “product of death” to their other lines?

I have two minor criticisms of the Floatron. Despite paying for itself quickly I think at AUD$450 here in Australia it is too expensive. I would suggest something closer to the US price of US$270. Having said that I would happily buy another one tomorrow at AUD$450, just my gut feels says it should be a little cheaper. The printed manual is well written and tells you everything you need to know but is written entirely in UPPER CASE. THIS MAKES IT HARD TO READ GUYS :-) (note however the on-line manual from the Floatron web site makes good use of lower case).

So in conclusion I think the Floatron is a great product, and ionisation is a fantastic way of maintaining a pool compared to chlorination. I figure with energy prices rising the energy costs of luxuries like pools need more attention. Ionisation is low on energy, low on chemicals, less chance of algae, less irritants, and less visits to the Pool Shop!


Low Energy Pool – How I used an old salt cell and the Floatron to reduce my pool energy consumption by 75%!

Peak Oil

Yesterday I helped two other grown men push a small van up a slight hill. Together, the three of us moved it maybe 30cm before giving up. Have you ever considered how much energy is contained in a single drop of oil?

For the past few months I have been reading all I can about Peak Oil. The basic idea is that the global oil supply will soon (around 2010) be less than oil demand. As oil is so fundamental to our lives (all transport, manufacturing, fertilisers for agriculture) this will cause big problems. Some people think modern society will end (literally), others predict a global depression, and some the death of the suburbs as the world reconfigures itself for a low energy lifestyle.

Here are some common predictions that I rate as plausible:

  • Oil prices will sky rocket, like over $150/barrel, causing the price of everything to increase, i.e. high inflation.
  • Stock markets tumble as every stock is based on the assumption of continuing economic growth sustained by cheap energy.
  • Widespread unemployment as whole industries collapse, i.e. “demand destruction”. Starvation in less developed countries (no fertilisers)
  • People with very high debt levels (the norm in Australia) will be in deep trouble. Overpriced housing markets collapse. The “perfect storm” for a modern economy.
  • As the taxation base decreases the government will be less help. For example they won’t be able to fund a switch to renewables, pay unemployment benefits, fix blackouts.

After a few months of research I am convinced Peak Oil is for real. While I am not in the survivalist camp (I think modern society will pull through) my best guess is that there will be very tough times for the world economy.

A powerful DVD on the subject which I recommend is A Crude Awakening. A really good book is Half Gone by Jeremy Legget, which nicely explains both Peak Oil and Global Warming. Or just Google on Peak Oil.

Governments (except Sweden) are ignoring the problem. This means that if Peak Oil hits, we will be largely unprepared, as we will have squandered the time required to prepare for transitioning from fossil fuels. So it’s probably up to individuals and communities to do what they can to cushion the blow.

You know what scares me about the Peak Oil problem? As an engineer I am used to solving problems. Software doesn’t work, you fix it. Hardware bug? Start debugging. You know that there is always a fix, somewhere. Peak Oil scares me because I just can’t see the fix. Anywhere.

So I am thinking about what I can do to “kick the carbon habit” and prepare for Peak Oil. Tactics like reducing debt, an electric vehicle (EV) conversion, improving my household energy budget, re-arranging my stock portfolio, and getting a grid-connect Photovoltaic (PV) array for my household electricity. All good stuff, even if Peak Oil isn’t for real. More on this later.

I am also interested in the possibilities of using Free Telephony to help a post Peak Oil world. I figure if people are moving around less and have less money, then low cost, low power telephony based on open hardware and software may be very useful for connecting the world.
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