Notes from Windward: #67


Update on Tank 2

Adding some aquatic plants

  May 30:

     At this point in the season, nature is calling the tune as the needs of the various systems we're working with determine what projects we work on when. At last count, we've got six different 'ponics systems under construction, each of which will serve as a test platform for different aspects of the work.

     For example, Tank 1 (the 40 gallon tank system) is all about the hydraulics--the challenge of getting the water to circulate reliably from the fish tank, to the grow tanks, and back.

     Tank 2 is our mid-size tank--1,250 gallons. We'll use it to study the chemistry involved in converting fish waste into a form that can be adsorbed by the plants. Another part of the chemical puzzle involves the interaction between the fish/plant chemistry and the concrete. Because of the complexity of the issues involved, our approach is to try and isolate different functions, solve them in isolation and thereby whittle the project down to a more comprehensivle size.

     Since Tank 2 was freshly poured last summer, we've been having the over-flow from our main water system running through the tank to facilitate the curing of the concrete while maintaining a neutral pH. It's been convenient in that so long as Tank 2 was over-flowing, we knew that our main water tank was full to over-flowing as well.

     As spring progressed, we noticed that Tank 2 had become home to a notable crop of mosquito larva, something we needed to deal with before they matured and became a pest. Rather than use an insecticide, we just went ahead and picked up a couple dozen baby gold fish at PetCo, and in short order there were no more larva.

     The next step will involve evicting our six new India runner ducks from their home in Vermadise (they have an instinctual sense that there are things outside of Vermadise that like to eat ducks, and haven't shown the slightest interest in venturing outside even when the doors are left wide open.

     The plan is to create a duck palace around Tank 2 so that the ducks can enjoy the water, and graze on the plant life--thereby lessening their need for other feed--but before we can do that, we need to get a good stand of aquatic growth going. The goldfish have provided enough waste to get the bacteria converting the ammonia into nitrites, and those nitrites into the nitrates--the form that can be utilized by plants--but without a healthy stock of water plants going, the system couldn't handle the extra load that the ducks would put on the system.

     Now that the weather's warmed up some, we're starting to see aquatic growth getting underway in the ponds that border the Columbia. Since it's always best to utilize locally adapted plants, the 'terns kicked off their shoes and went a'gathering. When their harvest was introduced into Tank 2, it quickly sank to the bottom, but by noon it had undergone enough photosynthesis to generate enough oxygen to float itself to the surface.


     The goldfish were delighted with their new food source, and spent the day nibbling on the green raft from below. We'll give it a few day's head start (duckweed can double in size in a day when conditions are right) before introducing the ducks to their new play area. Given the joy with which they approach any body of water, we're expecting the ducks to quickly make themselves at home in Tank 2.

  June 7:

     Well, as often happens when you're fiddling with the interaction between various living systems, things didn't turn out the way we planned. Instead of increasing in size, the mat of floating plants disappeared, and soon afterwards goldfish started to become hard to find. A bit of investigation revealed that the peacocks were to blame.

     So, the next trip to town we replaced the goldfish, brought home some more pond plants, and threw a security panel over the tank to keep the peacocks at bay. The upshot is that the peacocks have definitely earned a place on next week's menu.


  June 16:

     Just past Windward's western boundary, there's a hidden valley with a seasonal pond. We noticed the last time through that there were some interesting aquatic plants growing in the shallow water, so as part of our research into what sorts of local plants will do well as part of our aquaponics program, the 'terns decided to fetch a sample home and see how it liked living in Tank 2.


     It's been "hanging out" in Tank 2 for a few days now and seems quite at home. It's a good rule of thumb that the more living components a systems has, the more stable that system is. So far, so good.

  June 20:

     Jacque checked out the plant that the 'terns found and brought home for Tank 2, and we're delighted to not only have added a plant to our aquaponics system that will help condition the water for the fish, but which is also a perrenial food plant eaten by ducks, fish and people. Sagittaria latifolia--more commonly known as arrowhead, duck potato or wapato--produces edible, golf-ball sized tubers. Just the thing for a meander leading from the grow tanks back into the fish tank.

     For more information on wapato, Click Here.

  July 19:

     Passed another milestone today, and while there's a long way yet to go, Tank 2 is now cycling, sort of. We take our approach to these projects from the Japanese concept of kaisen which is a way of seeking perfection--another way to say sustainability--through an ongoing series of incremental improvements.

     But before you can do that you first have to get some part of the system up and running; in the case of Tank 2, that involves not only a series of pumps but also a timer system to control the pumps.

     This middle system will run the duck-enriched water in Tank 2 through three separate paths: the main growing beds, a secondary path that uses two 55 gallon Rubber-maid tanks to grow lettuce and duck weed, and a third path that will involve sprouting wheat to produce fodder for the milk goats--it's that secondary path that we've brought on line first.

     Under optimum conditions, duck weed has the ability to double in volume each day. The ducks love to eat it, hence the name, but if they had direct access they'd graze it down so quickly that even duckweed's prodigous growth capacity couldn't keep ahead of their appetite. By growing it in a separte part of the system, we'll be able to harvest duckweed daily by gathering up handfuls to toss into Tank 2 for the ducks to enjoy.


     Since ducks aren't the only critters who think duckweed's a tasty treat, and since we have a couple of yearling sheep who've figured out how to get out of the main pen and do a walk-around looking for tasty bits, the first thing we needed to do was to put up a perimeter fence around the new growing beds. We've found that orange safety fencing makes for a good "first fence;" if we find that the layout works for us, we'll go back and replace it with something more permanent come the rainy season. Right now our clayish ground is dry and hard; it's not a good time to be trying to drive T-posts into the ground.

     In a traditional aquaponics systems--where fish are providing the nutrients for the plants, and where you're trying to maximize the quantity of fish grown--the water is cycled every hour to keep up its oxygen content, but since we're using our breeder ducks to enrich the water, we're only cycling the water once every four hours. That's plenty enough to keep the plants moist, and consumes a quarter of the energy.


     The pic shows some of the components of our "duck-ponics" set up. At the bottom left is a blue pump which forms the prime mover for the system; the timer is laid open so that you can see the interior works.

  August 4:

     We're currently awaiting the arrival of a key valve that's needed to bring the main grow beds online, but in the meantime we're still tweaking the system. For example, you'll notice the odd staple-shaped outlets on the Rubber-maid tanks. They're a trick that we learned from the design of the barrel-ponics system--they make it very easy to adjust the level of the water in the tank. Instead of being limited by the elevation of the tank's outlet, the level of water retained is determined by the height of the top part of the staple-shaped outlet, and if you want that level to be deeper or more shallow, it just takes a moment to shift the angle of the outlet pipe to make it so.


  August 6:

     Left out one critical detail--in order for the depth adjuster to work, there needs to be a hole drilled in the top span. Without this hole, the depth adjuster turns into a siphon and proceeds to drain water out of the tank until the inlet sucks air and breaks the vacuum, thereby defeating the purpose of the adjuster .


  August 7:

     We're still awaiting the arrival of the magic valve needed to flood the duck-ponic's main grow beds, so we used the afternoon work session to modify the flood tank's lid to take two hydroponic grow flats. This will be the third path by which the duck-fertilized-water will be used--in this case to sprout wheat and grow it into green fodder for the rabbits and chickens.


     If this works out well, we're looking forward to using this technique to grow year-round fresh food for our rumemants using the waste heat from our electrical generation. That's a bit down the road, but in the meantime this set up will allow us to learn more about sprouting whole grains.

  August 8:

     I was elated to learn this morning that the magic valve had made it's arrival at the supply house in Hood River, but upon arrival it turned out that its design was such that it wasn't going to work in our application. The salesman was helpful--it was a learning experience for him too since in the ten years he'd been in the business, he'd never ordered a "NO;i.e. Normally Open" electrically activated valve before--but it was frustrating none-the-less. As Edison noted, in research you discover a lot more things that don't work than things that do work.

     So it's back to installing a variant of the flush valve that's used in toilets. The electric NO valve would have been an elegant solution, but we should be able to scale up the flush valve design to meet our needs.

Notes From Windward - Index - Vol. 67