Building the core of my mixed system

[Kobus Jooste]

When I first set this unit up, it comprised bites and pieces from a first trial unit that worked very well, but had to be moved.  It covered a larger area than what I had space for at home, thus the initial birth of my “cube quest”.  The system had a 1000 litre IBC and four gravel media beds in the new configuration.  The one media bed got used for all kinds of things – a DWC bed, a guppy fry tank and then back to raft before it got turned into the sand bed.  The other three have always been media beds. 

 

The ratio was just about spot on for Dr Lennard’s calculator, and the system worked very well until I started pushing the stocking rate.  At this point, I could not maintain good water quality even though my yields were still alright.  I decided to expand the growing area, but without any sumps, the amount of flooding I could do was dictated by the fish tank size.  Adding too many plant structures would not work without additional water volume.  I started tinkering with additional sumps.  In the first sketch-up diagram all of the components forming the core of my design can be seen.  I still have not added the two barrel halves under the grow bed, but the rest is in place.

 

 

 

The blue barrel (200 litre) turned on its side came first, followed by the recycled pool sand filter body.  Both of these contain floating media, while the peripheral growing structures are fed via a pump in the pool filter body.  The idea with the halved barrel sections is to fill them with gravel, and have the raised beds drain into them, from where they will overflow into the blue barrel sump.  The tall (150 litre) blue barrel will be connected with the unfiltered water line feeding from the IBC.  Water will be fed all the way to the bottom of the barrel, allowing it to rise through gravel and overflow into peripheral growing structures as filtered water.  This sump, as well as all the others, will not be cleaned.  In all, these structures have doubled my bio-filter and nitrification capacity, while only the half barrels will be planted.

 

 

 

Thus, I now have a core of an IBC, four raised media beds and five additional structures slotted into the open spaces created by the raised beds.  I can stand in the centre of the greenhouse and reach each bed, which to me is an improvement on the expansive design I had before.  I used to run the system 24/7 when it was stocked to the max with fish, but now that I have lightened the load, both pumps are on timer.  There is no additional aeration in the IBC. Eventually, I may add another IBC to the unit, but I first want to see how well this system performs with only the original fish tank.

 

In the next addition, I will go into more detail about what have been added to the unit in order to further exploit the available spaces.

 

[Terri Mikkola]

Do you think your nitrification problem is due more to an increase in heterotrophic bacteria rather than an undersized biofilter?

[Kobus Jooste]

Thanks David - someone on the forum sent me some sketch-up plans to look at and I had to download the software about two weeks ago to be able to look at it.  I find the software very intuative for the most part abd it helps that there are a lot of models on the internet that you can download and "expload" (what happened to "ungroup?) in order to get components.  Hats off to the guys at BYAP for putting their models up for use!!!

 

Terri - on the nitrification side, my system was just going to manage a normal load of fish.  According to the scaling calculator, (and my own experience running it before with a sump filled with netting and half the fish load), I was short on bio-filter and overall water capacity if the stocking density hit 20 kg/1000 liters.  It was doing alright (always had around 1 - 2 ppm ammonia and 8 - 10 ppm nitrates) when I could use buffered municipal water, but when I switched to rain water in a drought (that lasted 2 1/2 years) and the buffereing capacity of the system was exausted, keeping the pH under control became a nightmare.  I was loosing sensitive crops all the time.

 

This experiment was worth the outcome, but inspired me to have huge amounts of unplanted bio-filter in the current re-design just in case I want to try and have 20 kg/ 1000 liters again.  Right now I'm back to Low Density and everything is just starting to perk up with spring around the corner.

 

[David Waite]

Kobus great design work. If you used google sketch up you have spent some time mastering that software. Very cool.

[Terri Mikkola]

Nice design!  

What specific water quality parameters degraded after you increased your stocking density?