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Solids Management in Aquaponics

It is crazy to think the solids you are removing from your fish system might be going to waste, when in reality they are not with management of solids in aquaponics.  You could be using them elsewhere in your flourishing garden and fruit trees or you might give some thought to doing something a little trickier. The aquaculture engineer in me says solids must be REMOVED from Aquaculture systems.  You will hear me say this over and over, because it is true, there are mountains of science that agrees with me.   In aquaponics it is not about removal but management and this is why… Why Solids Management in Aquaponics? …and why not solids removal.  Let me share this proven and remarkable gem with you. The common talk is removing solids from aquaponics system, when in fact it is solids management in aquaponics that makes it work at its best.  With the combination of aquaculture and hydroponics, defining aquaponics, nothing more and nothing magic and special, we have to think of them as two when managing the system. We know solids have to be removed from aquaculture… and we know media beds in hydroponics do not manage the solids from the aquaculture very well.  I will tell you more about that in a minute. You need to think outside the box a bit and think of it like two or three boxes. So smash the box apart and look at the smaller pieces: aquaculture -> solids removal and  management -> hydroponics -> aquaculture Simple isn’t it! Let’s break it down. You will remember the Evolution of Aquaponics – Macro Sapian where we added an additional mineralization tank and that tank fed the dissolved nutrient from the solids removed from the fish system as need to the hydroponic system.  This makes a remarkable difference to the growth in your aquaponic plants. That growth difference is hugely visible.  It is doable by anyone and it is easy.  I have done it and on a huge scale.  The results were so surprising it caught my production team off guard.   To give you an idea, it increased our projected yearly production by 60%.   Check out this growth from seed in 3 weeks! Why Solids Management in Aquaponics? You have seen one of the primary reasons and the proof, it helps your system grow… do we need any other reasons? Yes we do. Media beds make for great bio filters but they make very poor solids filters.  The simple reason for this is they do load up with organic solids from the fish system.  I have seen this over and over.  I have seen it in pre-filtered beds as well.  Even using 50 mm gravel in aquaculture, they can only manage very light loads, like those seen in aquariums.  But we don’t have aquariums do we… You don’t need to do any of this and your aquaponic system will work just fine… for a while. It could be 6 months or 5 years but at some point the media bed with either show poor growth or you will have poor growth in your fish because you will have to reduce the feed.  Both of these issues are related to the accumulation of organics in the media bed which will begin to feedback ammonia into the system along with some other things living things do to not cope with. Solids management in aquaponics gives a level of control of the macro and micro nutrients in the system that you can not get with media beds alone.  I constantly read, my nitrate is too high, I have deficiencies in my plants and an armada of other nutrient related issues in aquaponics and the worst of all, why are my fish dying. Now I might cop a bit of flak for this, as I have in the past, even as recent as yesterday…  but I don’t write for those people,I write for you and everyone that wants to get crazy with their aquaponics and push the envelope of innovation and share that success with others. Plants do not grow with organic wastes and they are not fond of excess ammonia.  Every gardener knows, put fresh manure on a garden too much and it just burns the plants.  Compost it and your plants thrive. Two Approaches to Solids Management in Aquaponics Aerobic or Aerated.  Sounds a bit like exercise really.  In fact that is just what it is.  We use oxygen to burn or metabolize fats, sugar and energy.  In an aerated mineralization tank/drum you can effectively break down or dissolve quickly.  This process of bacteria (primarily heterotrophs) eating those tasty solids happens in about 35 days at temps of 35c.  So you could heat the drum, which may be needed in colder climates or leave it at normal air temperatures and it will take much longer. In an aerated digester it is no different to the permaculture gardener brewing up organic compost or worm tea.  The permaculture guys really know what they are doing.  One option that really tickles my fancy is the Vortex Compost Brewer… but it can just be a drum with an air stone in it.  The beautiful thing is you can use the brew for foliar spray should you want to fix issues in the plants quickly and add any other supplements in as needed without risk. Anaerobic non Aerated. This option is less power hungry but is much slower and will also produce gasses that are not ideal for living things when released.  So a stir up with something will help degas it before use.  Not a preferable method, but is energy is an issue this may be right for you.  Keep in mind it is going to get smelly…. Nitrite will be persistent in media beds that are full of organics which indicates a clean out is required The great thing about this no air process is it can be used with the aerated option if your nitrogen gets out of control.  When there is no air, the digester will degas nitrogen to the air reducing the nitrate in your system without risking your fish with nitrite.  Nitrite will be persistent in media beds that are full of organics which indicates a cleanout is required.  This is because of the denitrification process which sometimes gets stuck in the media bed. Either way the management of solids in aquaponics is a preferred way to be sure you are using every ounce of nutrient you are putting into the system and not losing it to backwash or gas to atmosphere. To wrap it up, solids management is: We remove the solids from the aquaculture system as quickly as possible We put these in either in a radial flow filter or from a radial flow filter into a 200 liter drum Then manage the solids drum aerated if you like or you can simply let the solids settle in the bottom Use that water, not the solids, to top up the nutrients in your aquaponics….

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