Hydroponic System Plans

(This is a repost from my political blog. I created this one because I was dumping a lot of material better suited for this area of interest.)

Today is another continuation in a series of posts about the most important agricultural system invented since the green revolution. The so called blue revolution as it's called incorporates organic and soilless techniques mixed with changing diets and consumption patterns. Many of these changes require work for the average consumer. However it is imperative for this shift to occur. Many people are part of this "revolution" in the growing urban farming movements and the general interests in all things "green".

One such technology that you can easily incorporate into your lives is simple hydroponics. Simple hydroponics usually is comprised of passive technologies. This can be as simple as a cup filled with medium (perlite, coconut hull, gravel etc.) and another cup to mix nutrients. Or it can be as complicated as making your own nutrients with worm castings. I personally recommend, with my 2 years of mistakes, using a grow tray (rectangular trench a few inches deep, rectangular pie pan or plastic ones found in a hydroponic shop) set up. More on this later.

This was not my first system ( in fact it was recently built) so if you want to go a different route here are the ones I have tried. My first system was a hydrofarm, my second a deep water culture tub (homemade), I built another one a few months later, then I built some simple seed starters made out of clay pots and hydroton/perlite medium. I soon after built my latest system which I will describe how to build now.

Materials: 2L bottle, medium, and grow tray. Nothing more is needed. 2L bottle can be recycled when you buy juice etc., medium can be bought at a garden store, hydroponic store etc. and a grow tray can be a used pie pan or a plastic grow tray bought at a hydroponic store for $2.

1. Gather materials
2. Fill grow tray with bottom medium, make sure to spread it out first. Make sure this medium is absorbent, I used pumice found at my local supermarket. This ensured oxygen was readily available and water was kept
3. Fill 2L bottle
4. Carefully place 2L bottle inside medium at a non-invasive location so that it reaches the bottom
5. Once certain that water is no longer flowing through the bottle place hydroton (brand name--it's just clay pebbles in a firing process) on top of the of the bottom medium so that it covers it
6. If not already done place in a ideal location ( near the sun)
7. Plant, enjoy, repeat*

Remember to fill the bottle once it runs out of water and do nutrients to the requirements of the plants listed on your nutrients or by looking at the plants.

Now if you want to build a deep water culture system you need only a rubbermaid tub, an aquarium airstone (what produces the bubbles in an aquarium) and medium.

Materials, rubbermaid tub, I used a 18 gallon one; knife; net cup (yogurt cup with holes); airstone; air pump; vinyl tubing; medium.

1. Gather Materials
2. Outline the smaller side of the net cup with a sharpie
3. Use the knife to make small incisions in the plastic top
4. Slowly and carefully use the knife to go across the surface of the circle
5. Make the cut so that it's close to round
6. Insert the net cup to make sure it's done correctly (it should fit right in)
7. Hook up your airstone with your air pump with vinyl tubing
8. Put airstone in the middle of the tub
9. Fill the net cup with medium that wicks
10. Fill the tub with water
11. Place net cups in the hole
12. Plant, enjoy, repeat

*Quick update: the bottle method works fine, but the system, in general, can really only be used for herbs. Although, last year, I managed to get a few (5) soybeans from it. All in all, it is a pretty cheep form of hydroponics and it is a welcome addition to my garden.

Media in Aquaponics

Correctly choosing your medium/media (media is the plural form of medium) is perhaps the greatest challenge any aquapon* can face in the making of an aquaponic system. The medium will determine your success, among some other factors. Too much carbonate buffer, and the pH is too high, too low, and your pH will wildly fluctuate. In fact, the single largest cause for failure in an aquaponic system is the choice of a high carbonate medium. There are two, productive, things you can do, 1) stop growing plants and filter the water with a mechanical filter or 2) replace your medium. Both of these are incredibly expensive--on the order of hundreds of dollars (USD) for a recommended sized system (1000L for the fish tank and equal volume for the growbed). This will depend on other factors, but it is generally that expensive. This is a problem that can easily avoided, however.

Firstly, though, let's understand some of the water chemistry happening in an aquaponic system. The pH of a system is recommended at 6-7. This differs from the recommended pH for a hydroponic system (5.5-6) because aquaponics is a living system. In aquaponics, the pH must be a compromise between fish, plants, and bacteria. Bacteria and fish prefer slightly basic conditions, while plants prefer more acidic conditions. Nitrates, Nitrites, Ammonia/Ammonium are also present. These are measured in a unit called Parts Per Million or PPM, which is equivalent to mg/L. Nitrates are taken by plants as usable Nitrogen for proteins, so a sign of a healthy system (well-balanced) is a Nitrate level of around, but over, 0mg/L, but Nitrates can safely rise to well over 500mg/L for tilapia species.   However, ammonia, ammonium, and nitrites should never rise beyond around 5mg/L for the sake of the fish. Even then, it's a crisis in your bacteria colony. 

The pH, however, will be what is dealt with most directly in a choice of medium. A high carbonate medium, limestone and marble, will raise your system's pH to a level that "locks out" iron for plant use. The cause for this stability in pH (at a high pH) is something called a "buffer". A buffer is a conjugate acid base pair, such as H2CO3 and HCO3-. The first is Carbonic Acid--the acid responsible for ocean acidification as CO2 levels rise in the atmosphere. Carbonic Acid is in a equilibrium with the bicarbonate ion. This means the levels don't change between them, even as the reaction is happening (the rates of reaction between them are the same). Carbonic Acid is produced by fish breathing out CO2 through their gills. This CO2 gets dissolved and turns into Carbonic Acid. When you add excess CO3 or HCO3 in your medium, you are causing the reaction to deplete the reserves of hydronium ions (H3O-) which is responsible (along with OH-) for changes in pH. Therefore, it will take a lot of H+ (produced by your bacteria) to get rid of all that base. In the meantime, your pH will be nearly stable--over 7 for this substance. 

This is, in fact, the reason why most systems that end up failing fail. There's nothing you can do about it other than the options above. However, there is a way to prevent this from happening to you, and it's simple! You could pay for a high-quality, inert, medium such as clay pebbles, expanded shale, etc.; or you can do the "fizz-test". First pointed out to me by TCLynx on the Aquaponics Community , it's a way of determining whether the gravel you are buying has carbonates in it--pour a cheep, weak acid on it. Usually, acetic-acid (vinegar) is used, because it's cheep and can be found anywhere. I personally think HCl would be more fun, but to each their own. If it, well, fizzes, then DON'T buy it. If it stays inert, feel free to order it--gravel is usually cheaper than other mediums.

In my opinion, gravel and water is the best media combination. One gravel bed and a few deep water culture grow-beds. But, that truly is a point of prejudice, not scientific fact.

Happy Gardening!--Blackberries are for Picking

*meaning someone who practices aquaponics