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Water Flow At Basin View Integrated Garden

Releasing the water flows to the Basin View Integrated Garden,  I wanted to example you do not need to be entrenched in the current beliefs of how to set up an aquaponic integrated garden.  In the backyard the possibilities are huge and the more I look into it, possibly endless.  It is my hope you can see there are many other opportunities to explore with integrated gardens, many well and truly break some “rules”. The point being, when rules are bent in organic systems, compromises will have to be made.  Like in the case of no pre-filtration to media beds, the amount of fish you grow will have to be reduced. In this integrated garden the water flows from the fish tank to the floating raft which has already thrown a spanner in the works because the risk to the plants on the floating raft eg: solids building up on the roots… but as many know I care more for the fish than I do the plants for good reason.  Which you will see in the following long winded explanation. [heading] Water Flow in this Integrated Garden [/heading] The water flows in this integrated garden have been set out like you would passive filtration for an aquaculture (low density) system.  We utilize each of the growing systems to preform a step in solids and bio filtration instead of having dedicated filters.  Permit me to break it down a little: Aquaculture tanks The aquaculture tanks are well aerated and the exchange on the tanks is relative to the oxygen requirements of the density of the fish grown.   That oxygen is expected to be 4mg/l on the outlet to the tank which is well below saturation and the key to the entire system is oxygen so I want to put oxygen saturated water into the media beds.  This is where the floating rafts kick in and contribute to both settling of solids and additional oxygen. Floating rafts The floating rafts primary function is to act as the settling chamber for heavier solids (fish poo and wasted feed) to drop out of the water.   This is the first stage of passive filtration in fish systems, excluding those using rotating drum filters. The water enters in the center and has to travel passively over 5 meters each way to then enter the clay beds. During that time majority of the solids will be captured by the floating raft.   Indeed you may get some build-up of solids on the roots of the plants but that is a minimal risk to take as it does not threaten the systems health.   I have increased the depth of the rafts to 500mm to help reduce this risk. If we get a reduced growth in the leafy greens on the floating rafts, it is an acceptable compromise. A point to note about the floating rafts is the crayfish.  While others like to grow an assortment of bacteria, fungus and worms or other non-edible creatures in their systems, I like to grow food and do so in the most efficient way. So the only compromise is the minimal risk to the plants of solids building on the roots but that also provides the system with several other benefits as the water progresses through the aquaponic system. The floating raft tanks are heavily aerated from one end to the other using an aquaculture air tube (like the garden leaky hose) and the crayfish will make short work of any solids settling out. Don’t make the mistake freshwater crayfish do not contribute solid and dissolved wastes to the system, they do relatively the same as fish.  So any additional load of crayfish needs to be accounted for.[pullquote style=”right”]Crayfish Eat Wasted Feed and Poop By the way the waste is perfect food for the crayfish. That is the point, the 30% wasted feed from the fish, automatically feed the crayfish in the floating rafts which is utilized for growth and produces ammonia.[/pullquote] Generally people will do this in reverse and clog up media beds with anaerobic organic wastes; in this case we prevent the need for cleaning the media beds.  I mean really, there is 90 ton of gravel and 6 cubic meters of expanded clay. I am not certain the folks at the retirement village would be too keen on digging it out and cleaning it…. The floating raft can be drained and hosed out if need be though I think highly unlikely.  The inorganic sludge that is generally left over can be removed if needed. The Media Beds Next in the loop is the clay media beds, which look like clay beds but really only have 100mm of it top dressed because it is soft on the hands (it is really nice on the hands but so is soil).   I have to say the expanded clay is enormously expensive and the energy costs to make it would put it bordering on unsustainable. For example 6 cubic meters of it at a hugely discounted rate (50% off retail), cost around 50% of 90 ton of gravel, topsoil, sand and garden mix put together! I digress… The media beds, like I said have 100mm of clay dressed on top of 300mm of gravel.  This provides a massive surface area for filtration and nitrification.  With 1 cubic meter of clay and 5.4 tonne (or 3.6m3) in the six media beds making a total of 6m3 expanded clay and 22m3 of gravel,  I expect the filtration to be exceptional which it has proven to be.  The media bed is not the end of the filtration, there is another 40m3 of gravel to go through. So the media beds act as part of the bio-filtration in the system and because they have not been loaded up with organic solids, they will be very efficient in comparison to putting media beds in front of floating rafts.  This is a very important stage in the filtration because we are looking to convert the ammonia from the fish, crayfish and the mineralization of solids to nitrate which the plants will take up more readily. Something to think about: If ammonia makes up more than 20% of the total nitrogen in the system, it will be, poisonous to plants (phytotoxic), and no doubt the fish and crayfish may struggle too. On a side note, we did the very same thing in the Coombabah Aquaponic system where the floating raft acts as the settling chamber and it is filtered on the media beds.  They managed to grow plenty of crayfish which are on their second generation and all variety of greens, including beetroot, which is very odd to say the least as generally you don’t grow root type veggies in floating rafts. The media beds act also as a polishing filter to remove some of the finer solids before the water enters the Earthan Beds.  It is important to remove as much of the solids as you can before entering the Earthan Beds because they will be low in oxygen under all that media (soil and gravel) and adding more organics could block the flow or at least force a channel flow through the media reducing their efficiency. The Earthan Beds These are a unique grow bed designed by me to be an inexpensive alternate to other growing mediums.   As the growing medium is soil which can be seen as a problem for those used to other growing mediums but it is not that foreign to those growing in soil all their lives, like the residents which will be using this garden. Below the 10m3 of garden soil, where the water runs 24/7, is 7m3 or 10.5 ton of gravel in the 6 Earthan Beds.  The total of the media in these 6 grow beds is a whopping 60m3 of soil and 40m3 of gravel (60 ton). The soil in these beds primary function is to grow food.  No seriously, the soil provides a complete range of macro and micro nutrients for plant growth. Where aquaponic system using inert (neutral) media like expanded clay they lack potassium, calcium and iron along with a few micro nutrients for healthy plants. This is not to say aquaponics systems using these grow mediums do not grow well; it does however take up to a year to really start to perform. During  start-up time nutrient are generally added in the form of Seasol and other organic fertilizers.   This can be because when you start an aquaponic system you have very small fish in it and they produce very little waste or nutrient for the plants.  It is also because the medium has nothing in which encourages plant growth except water. These Earthan Beds are already performing with 10 gold fish in 50,000 liters of water because the carbon and nitrogen and other nutrients stored in the soil are released slowly.  There is a minimal risk that during heavy rain the nutrients will be washed out, however, the gravel under the beds will store majority of it and the system is designed to overflow. Opposite to inert media, the soil will contribute to the overall nutrient profile in the gardens when it does rain, which I can testify to the rain on the south coast NSW.  In media systems that have a build up of anaerobic solids built up in them, if they are out in the rain the chances of disturbing and redistributing those nasties through the system is high. The dumping of solids back into the system is very much the same thing that happens during summer storms where the excess run off into aquaculture ponds can introduce new organics and stir up the bottom (benthos) of the ponds and create a very oxygen poor environment and fish quickly die. Getting a little off topic… The Earthan Beds are an extra source of a broad range of nutrient and permit the gardener to safely add nutrient sources in the form of mulches (to keep moisture) and other organic sources.  Basically, the Earthan beds can be considered as a self-watering, nutrient storage for the entire system. Further Filtration From the Earthan Beds the water is finely polished passively and enters the two water storage tanks by gravity.  In the first of the two tanks there is more kaldnes bio-media to deal with any ammonia produced by the Earthan Beds and act as a redundant bio filter should the garden beds, any of them, be bypassed. There is a bypass on each tank system. A tank system consists of one aquaculture tank, one outer ring with one floating raft and two media beds and two Earthan Beds.  These can be bypassed in bulk in each set or the entire garden.  While it would be rare to bypass the garden complete or even partly, at some point the fish may need treatment for parasites or other issues and Murphy’s’ law says if it might happen it will happen. The two water storage tanks are heavily aerated to charge up the oxygen for the next trip around the system and prevent too many solids settling out in them. From there the water is pumped back to the fish tanks in the center of the garden and it travels on its gravity journey through the garden again. There is a few other “tweaks” in the system but that is the gist of it.  If you are thinking about using soil as a medium at home in your backyard aquaponics, plugging in a wicking bed will do much the same thing. Happy Harvesting. Paul…

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