The last item we will need is a grow media. We will need a good amount too. Very roughly 15 cubic feet (112 gallons, 425 liters). Yeah.. So thats a
thing. One of the best is expanded clay, like Hydroton.
However, if we add that up.. We are
increasing our cost dramatically. The best method I have come across is a layered approach. We put larger river rocks at the bottom (3/4"-1"), pea
gravel to fill in the rest of the bulk, and then a final layer of expanded clay. The actual ratios are not hugely important, but try to make most of
it the pea gravel and expanded clay. I would suggest 100 liters of the Hydroton, and then go from there. We can purchase the pea gravel and river
rocks online, but sourcing them locally will be extraordinarily cheaper (shipping costs!). The only thing to watch out for, and this is important, is
that they have very, very limited amounts of limestone. Ideally none at all. Limestone will mess with our pH, and thats a pain. We can test this by
using vinegar; if it bubbles, weve got limestone. Generally, we can pick this up locally for about $1 per gallon. This is likely to be the single most
expensive item in the system.
A notable mention here is something like a swirl filter. In a smaller system like this, we dont really need to worry about it, but they are pretty
easy to put together ourselves. We can also purchase them, and they can be made as decorative parts of the system, like waterfalls. Its a function
over form type deal, but why not have both if we can swing it?
Now onto livestock & crops:
The general rule of thumb is 3-8 gallons per pound of fish. Thats a big range, but its dependent more on the bacteria colonies and the growbed being
able to handle the nitrification process. We can technically raise any fish we want, but since the goal of *this* system is year round production for
supplementing a family, we will be looking at Tilapia and freshwater Shrimp/Prawns. They both like the same temp regions, the same pH regions, tend to
get along well (enough), and can grow to the harvest point quite quickly. For fish, we usually look at the 1 pound mark and for Tilapia, that takes a
bit over 6 months and for shrimps/prawns it takes 4-6 months. Do note that we arent looking at a whole lot of prawns, less than half a dozen. It might
even be better to look at them as tank cleaners more than an actual food source. Breeding can happen, but for higher chances of success, something
like a prawn hatchery can be built.
The temp range for Tilapia is going to be 82F-86F (28C-30C) and they like a pH range of 6.5-9. General freshwater shrimp & prawns will thrive in
~60F-84F (~15C-29C) and a pH range of 6.5-8. Pulling out our calculators here, we can see that we want to keep our system at 82F-84F and 6.5-8 pH. We
can actually go outside these ranges, by more than one might imagine.. but not for too long. To keep this in check, as well as keep our eyes on things
like nitrites and nitrates, its best to get a testing kit like the industry standard API Master Test
Its also not a bad idea to get pH Up & Down.
As opposed to normal aquariums, or normal
hydroponics, the system should take care of itself beyond that!
Crops are a massive topic all their own. Im hesitant to go too deeply into it, actually. Generally speaking, things like corn will not do great.
Likewise, anything that grows a lot of roots very quickly can be difficult to deal with. Crops like taters arent a good choice either, but they can be
grown in a Tater Box.
Other than that, there really arent too many
limits other than creativity and how much time you want to put into it. Something like strawberries can do great, but they can require a lot of plants
to actually have meaningful yields. With that in mind, I would personally recommend some nice leafy greens like a Kale, and trying to fit some
medicinal plants like artemesia annua in there too. Having something like a germination chamber can help a lot as well.
Now we get to the actual construction. Ill only give some general guidelines here. There are no steadfast rules. 1" PVC is your friend, and is a
wonderful construction material in general. You want to avoid too much metal, as it can mess with the pH, but a little here and there isnt a big deal.
To create a tank and a growbed from the IBC Tote, we have to cut it. Its easiest to separate the inner plastic from the outer metal cage for this
process. To create the growbed, we are going to measure down 14" from the top of the plastic tank and cut all the way around. We will do the same for
the outer cage so that both the growbed and tank have the support. Dont worry too much about precision, unless your OCD will bother you later on..
We want to set it up so that the water cycles from the livestock tank to the growbed and back again. The simplest way to do this is to place the
growbed directly on top of the tank. This can be done anyway you want, but make absolutely certain that whatever you build can support the growbed
with media, plants. and water! It can also be a good idea to make a cutout on the front top of the tank so we can access the fish & prawns easily.
The bell siphon is easiest to install right in the middle of the growbed. This will just drain directly into the fishtank. Then, to get the water back
up, we need to run tubing from the submersible pump in the tank so that it will pour out into the growbed. This can be done with PVC quite easily, and
the easiest would just be a single pipe running from the water pump vertically to a 90 degree fitting that pours it into the growbed.
Our air pump goes into the livestock tank, and will pretty much work anywhere we put it. However, if we are going to make life a bit easier on the
fish through things like structures and objects (which can also help the prawns/shrimp hide, the younger fish run around, etc), we need to make sure
that wherever it goes isnt obstructed.
Our heater can technically go anywhere, but to produce as even temps as possible, we should place it somewhere that will circulate the most, but also
in a spot where the fish do not have easy access. Because we are dealing with a (roughly) square tank, this presents a bit of a challenge. However, we
can divert some water from the water pump, or air from the air pump, to move the water however we wish.
Now we just place the media in the growbed in whatever fashion we desire, filling it up about 12" The idea isnt to completely submerge things though,
so keep that in mind. We want an inch or two of media that stays dry to prevent the growth of algae, etc. There are other ways to achieve this too,
but the most straightforward is to leave the top bit dry. Now, before we really get going, it is a good idea to try to run the system to rinse the
media. We can even build a little PVC pipe system that runs where the bell siphon would be, rinse it with a hose in the grow bed before we even
construct the system, use sieves, etc. The idea is to wash away as much debris as possible.
edit on 6-6-2020 by Serdgiam because: (no reason