Aquaponics Water
STEC Systems are all about the water. Water quality is a high priority and insures the growth of healthy fish and plants. There are several factors that go together to create the perfect water environment. They include the pH, Ammonia, Nitrite, Nitrate, Bacteria levels, Temperature, Oxygen levels and Alkalinity and Source. An imbalance of any one of these factors can cause the water quality to drop to harmful conditions for the fish and/or the plants.
Water Quality Consists of these Eight Important Components:
- pH
- Ammonia
- Nitrite/Nitrate
- Bacteria
- Temperature
- Oxygen
- Alkalinity
- Source
STEC Growing Systems are all about the water. Water quality is a high priority and insures the growth of healthy fish and plants. There are several factors that go together to create the perfect water environment. They include the pH, Ammonia, Nitrite, Nitrate, Bacteria levels, Temperature, Oxygen levels and Alkalinity and Source. An imbalance of any one of these factors can cause the water quality to drop to harmful conditions for the fish and/or the plants.
Above is one of our STEC Growing Systems. It’s a FGS-20 with a Module-20 added, which makes it a  four Grow Bed System, each able to hold 11 sq. ft. of growing space. When in full operation, the water in the tanks circulates through each of the beds and then returns back to the fish tanks.
What is pH?
The “H” in pH stands for Hydrogen and the “p” stands for the power of that Hydrogen –the concentration of hydrogen ions in a solution. That Hydrogen concentration is very important for living things because Hydrogen ions are positively charged and can, therefore, alter the charge environment of other molecules in a solution by putting a force on the molecule causing it to change its normal shape. For a protein molecule this is crucial because the shape of a protein is related to its function. A low pH count corresponds to a high hydrogen ion concentration and a high pH count corresponds to a low hydrogen ion concentration. A substance that when added increases the concentration of hydrogen ions (lowers the pH) is called an acid; and a substance that decreases the concentration of hydrogen ions (raises the pH) is called a base. There are also substances that enable solutions to resist pH changes when an acid or base is added. These substances are called buffers. Buffers help organisms maintain a relatively constant pH. Pure water is considered neutral with a pH of 7. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are said to be basic or alkaline.
Tilapia and the nitrifying bacteria prefer a pH range of 7-8, which is on the alkaline side of the scale. The best place to keep you Aquaponic system pH level is between 7.0 and 7.5, which is a compromise for the fish, bacteria and the plants as the plants prefer a more acidic environment. Drastic shifts in either direction can be lethal to all the living organisms in your system. So watching pH levels is very important.
What about the Ammonia Levels?
All urine contains ammonia and tilapia urine is no exception. Some ammonia is even excreted through their gills; and ammonia also comes from the break down of their solid waste. In a lake or pond, the ammonia levels are of no concern because there is so much water compared to the number of fish; but in a fish tank, ammonia levels need to be carefully monitored because ammonia is toxic to the fish.
Bacteria? How does it relate to the Nitrite and the Nitrate?
There are actually three crops in an Aquaponic system–the fish, the plants and the very important beneficial bacteria. It’s the bacteria that convert the toxic components of the fish waste, like the ammonia, into a form of nutrients that the plants can use. There are actually several types of bacteria living in an Aquaponic system; and each one performs a specific job. Without them, Aquaponic food production would not be possible. As an Aquaponic farmer, you have absolutely nothing to do with controlling or monitoring the bacteria. It all happens just as it should–naturally as a part of the process of life itself.
Autotrophic Bacteria is a term that describes two function-specific bacteria. The first one, nitrosomonas, uses oxygen to convert toxic ammonia into Nitrite; and the second one, nitrobacter, converts the Nitrite into Nitrate. There is some debate as to the names of these two bacteria. Since both the ammonia and the Nitrite are toxic to fish, these two bacteria are crucial to the system. Nitrate being much less toxic than ammonia, can be tolerated by most cultured fish until it reaches very high levels. Once this autotrophic bacteria process is complete, the resulting Nitrate molecules are controlled by the plants themselves.
Heterotrophic Bacteria is the term that describes how specific bacteria convert solid fish waste into ammonia and other elements. These two types of bacteria occur naturally. They habitat the plant roots, the water, the tanks, the pipes and the media (See Grow Beds) in an Aquaponic system. Their growth and density depends on the water temperature, pH, surface area, flow rate and salinity (saltiness). Since the bacteria are not visible to the human eye, you can’t measure or monitor them. So, the only way you know your bacteria crop is a healthy one is through testing the levels of ammonia, Nitrite and Nitrate, which you can do.
What happens when the Fish are introduced to the system?
The first thing that happens when you place the fish in the water is they continue their natural cycle of elimination of urine and solid waste; and guess what, the ammonia level rises (for about the first 7 days). Then as the ammonia level starts to fall, the nitrite level elevates; and you know your friendly little nitrosomonas have been busily converting ammonia to nitrite. They do this for another 7 days until you see the nitrite level start to fall and the nitrate level start to rise as your nitrobacter go into action converting nitrite to nitrate. After about 14 days, your system will stabilize and the nitrification cycle will proceed naturally indefinitely. At that point, your job as the Aquaponic farmer is to regularly monitor your ammonia, nitrite and nitrate levels so you know your water quality is the best it can be for both your plants and fish.
What’s the ideal Water Temperature?
The ideal water temperature is a variable that depends entirely on what fish species and what plants you are growing. Tilapia thrive in temperatures between 70-85 degrees F, but most Aquaponic farmers keep their Tilapia tanks between 72-78 degrees F (depending on the sub-species of Tilapia), which is a compromise between the fish temperature requirements and the plant requirements. Aquaponics is a multi-faceted system in which one component affects one or more other components. Water temperature is a cross-affecting component. It affects the oxygen levels, the amount of unionized ammonia (ammonia not yet converted to nitrite ions) and the amount of salinity (salt) in the water. Warm water has less oxygen than cold water. It can also have a greater proportion of unionized ammonia and more salinity than colder water.
What about Water Oxygen?
Even water life needs oxygen. In fact, the water oxygen level, called dissolved oxygen, is one of the most important water quality components in an Aquaponic system; and it needs to be monitored often. The best levels of dissolved oxygen are close to 80% saturation, which translates as 6-7 milligrams per liter. Levels below 3 milligrams per liter are a hardship on aquatic life and levels under l milligram per liter are deadly. The water temperature affect the dissolved oxygen levels. Cold water has more oxygen than warm water. Too many fish in the tank can also deprive the fish of dissolved oxygen as well as too much food. If the water is saline, it also has less oxygen than does fresh water.
When your fish are oxygen deprived, they let you know by exhibiting the following traits: appetite loss, surface gasping, inflow pipe gathering, retarded growth, susceptibility to disease and succumbing to parasites.
There are two ways to test your oxygen levels–the cheap way and the expensive way. The cheap way involves an inexpensive Test Kit that gives you the DO (dissolved oxygen) level. It takes a little time and is not precise but gives you a ball-park number. Then there’s the DO Meter, which costs anywhere from one hundred seventy to a thousand dollars. It’s fast and precise for a price.
What does it take to be a backyard Aquaponic Farmer? Or do you want to be a Commercial Farmer?
Several years back, the Air Force ran some tests to determine which airmen would make the best paratroopers. After putting their target subjects through an entire battery of trials, exams and exercises what was determined was as simple as this: The best paratroopers were the airmen who really wanted to be paratroopers. Needless to say, to be an Aquaponic Farmer you have to want to be an Aquaponic Farmer. You don’t have to be a water scientist, an engineer, an advanced horticulturist. But you do need to be responsible for taking measurements and adding what’s required when those measurements indicate it.
Ou STEC provide the water quality measuring devices and starter Additives you’ll need so becoming a food independent Aquaponic Farmer is actually a no-brainer. All you need do is to add your choice of fish and grow some veggies.
What is Alkalinity?
There is much confusion around the terms Alkalinity and pH as they are often mistaken for each other. Why, because they are both measurements, but they measure two different things which are related but not the same. Alkalinity is a measurement of water’s ability to neutralize acids also called water’s buffering ability so it refers to the ability of water to resist change in pH. These buffering materials are called bases and primarily include bicarbonate and carbonate. If you read the pH section above, you see that pH is basically the measurement of the concentration of hydrogen ions in water, in terms of acidity or alkalinity. Water with low alkalinity is very susceptible to changes in pH. Water with high alkalinity is able to resist major shifts in pH. Alkalinity is measured by titration. An acid of known strength (the titrant) is added to a treated sample of water. The volume of acid required to bring the sample to a specific pH level reflects the alkalinity of the sample as indicated by a color change. Alkalinity is expressed in units of milligrams per liter (mg/l) of calcium carbonate. The acceptable level of alkalinity in aquaponics has a broad range between 50 and 300 mg/l. Your job as an aquaponic farmer is not to concern yourself with the science.
Source–Whence Comes Your Water?
Source may be last on this list; but it is by all means not least. When you unpack and place your Aquaponics USA food-growing system, the first thing you need to decide is where to put it. Now you may think that the second thing you need to do is fill it with water. But there’s an important interim step right here. You need to know what’s in your water before you expose either fish or plants to it. There are four possible sources for water. They include: well water, municipal water, rain water or water purified by reverse osmosis, ozone or UV. You need to have your water tested by a laboratory that specializes in water for agricultural use to make sure it’s not going to be harmful to your fish, veggies or bacteria. Ideally, it would be best to have this done while you’re waiting for your complete, compact food-growing system to arrive.
Remember our discussion about pH above? Your source water should have a neutral pH of 7 or at least be in a range of 7.0-8.0. Well water can be superior to municipal water because it often has trace elements like calcium, chloride, sodium or iron. These trace elements in small amounts can be beneficial as these elements are sometimes deficient in an aquaponic system. Municipal water often contains chlorine which is toxic to both your fish, nitrifying bacteria and your plants. If you know your water source has chlorine, you must arrange to have it removed before placing fish and/or plants in it. There are several ways to accomplish the removal of chlorine including: purchasing a water purification system for your entire home so not only your fish and plants are chlorine free but your family is also. You can also purchase a unit that attaches to the hose you use to fill your system. Chlorine can also be removed with lots of aeration. You let your system run for a couple of days with only water in it to allow the chlorine to dissipate. You need to use a chlorine test kit to signal when your water is safe for your fish, plants and bacteria. A safe level is less than 1 mg/l of chlorine. Another toxic element in municipal water is chloramine which can be removed using a catalytic water filter.
There was a time when rain water was an excellent source of water for an aquaponic farmer; but it’s no longer reliable and can often contain contaminants especially in large cities where “acid rain” is a known occurrence. We also do not recommend reverse osmosis water unless you’re supplementing it with minerals due to the fact that it is lacking in anything that may be beneficial to your plants or fish. If your water is highly alkaline, then an RO unit may be required. We have found it necessary to install one of these ourselves due to the high alkalinity of our well water. Is is advisable to mix the RO water with source water in order to add in the source water minerals. Once your system is filled with good source water, you need to circulate your system for a day or two to bleed off any gases that it may contain. This also allows you to monitor and test your system to make sure it is working properly before adding the fish and the plants.