Are we designing for biochemical processes?

[Kobus Jooste]

A number of discussions have prompted this thought pattern.  I credit the bulk of this current burst of cranial activity to a comment made by Terri Mikkola (Thanks Terri) regarding the population mix of bacteria responsible for nitrification and those responsible for the mineralisation of solids.  In UVI and Friendly style systems the multi-stage filtration system ensures that there is a separation from the zones where masses of solids accumulate.  In my current mixed system re-vamp, I have a number of media filled structures (Gravel and netting) that act as first or second stage filtration.  In gravel only systems, the addition of worms to the beds can greatly reduce the volume of solids building up on the gravel surface and therefore also make for a relatively good combination of nitrification and mineralization, but here is my current thought:  Do we provide enough?

 

We characterise ourselves variously as plant or fish orientated folk, and describe fish tank to grow bed volume, but should we not be filter orientated folk?  While it is great to be able to circumvent complex filter design in more basic units there is perhaps a reason why multi-stage filtration is so effective.  When AP matures to the point that we have years worth of data on the performance of different designs, we might get the answer I am looking for now. 

 

Until we get that information, my current philosophy in mixed design is newly influenced by my thoughts on effective use of space.  There is obvious power implications of lifting water over a slightly greater distance to create a raised bed with filtration below, but if space is a problem, then it may be worth considering.  If space is no concern, what is the operational efficiencies of a unit with minimum (not too little, but just enough) vs one with maximum filtration? By the time I'm done, my filter structures may be almost double that of my fish tank (I consider media filled beds / towers as part of filtration).  For me, this boils down to having enough space for sufficient nitrification / mineralization bacteria to find a niche and do their work.  And then some as insurance as I do not want to be in there cleaning it all every week. 

 

I attached great value to a few second or third stage tanks / barrels just filled with floating media / nets in my new mixed system, but lack data at present to verify the results.  Time will tell, but I think the question of filtration is a very important and often sidelined aspect of aquaponics.

[Kobus Jooste]

Averan, in my home system, I will plant the gravel lightly but never go to the vision of total plantless gravel.  I have a design for a large unit though that operates exactly how you picture it - concentrated solids from aquaculture and all the processing scraps from the production side going into the gravel with worms. 

[Averan]

Kobus, I know you are planning to put worms in all your media-only (no plants) filter beds, but have you thought of feeding those worms with compost veggie scraps?  This takes it up one notch from just a passive filter where the worms feed only on fish poo and makes it more of an active vermicomposting filter.

[TCLynx]

Sure and when you already have certain parts in and the extra space available happens to be under a bed, use what you got!  That is why I say each situation will dictate the best method for...

 

It is always interesting to hear the results of experiments that people run and some of the experiments that people have been running have definitely changed my viewpoints and methods over time.

[Kobus Jooste]

TCLynx: I'm not sure if any company is going to start selling rubber maid type containers here any time soon but until then, it is the blue barrel, the IBR and the custom stuff I can work with.  When I started looking into AP I saw the 30 cm bed configuration often enough to srtart with it, but now I am incorporating some deeper structures too.  The home unit is a retrofit more than a redesign, thus the shallow grow beds stay, but I agree 100% - the best way for surplus filtration on a tight footprint is deep beds.  I'm looking at going a bit further though - wanting to have gravel and net / floating media to try and mimic the multistage worm / nitrification / mineralization seperate theory I am looking at seriously now.  I't is not a unanimously accepted view, but I support the opinion of people that say that it perhaps better to cater for the different stages in different structures, particularly in smaller units.  That is what this retrofit is supposed to investigate

[TCLynx]

I've always felt that in the public relations descriptions of aquaponics, the filtration (which it me is the most important part of any bio-ponics) gets terribly short changed.  Now while I originally got into this from the hydroponic side I was very quickly converted to the idea of twice as much media volume in relation to fish tank volume method and I think I'm a bacteria oriented aquapon.  To get more filtration while saving on footprint, I like the deep grow beds.  The easily available materials for me make deep grow beds easy where it would be more costly/difficult to have a raised grow bed drain into a separate filter/sump below so I have lots of deep gravel beds.

 

Where materials are different, then different methods will be more appropriate.