Aquaponics 101 Part 7: Improving Water Quality
This is the seventh in a series of Tutorials that are going to teach you much of what you need to know about Aquaponics. So, if you’re curious about the most amazing food growing technology on the planet today, complete this Tutorial series of educational posts on Aquaponics 101.
In Part 1, “The Bio-Chemical Process”, I wrote about what Aquaponics is and why it is important to Preppers (those preparing for what is about to come down the pike). An AP system will allow you to grow food for you and your family year- round as long as your AP system is in the proper environment. I also gave a description of the biological processes involved that make Aquaponics work.
In Parts 2 and 3, "System Design", I wrote about the components of a basic system. To quickly review, I wrote about the need for a bio-filter and that it is usually combined with the grow bed to form a single AP component called the grow bed, which is the most important part of an Aquaponics system. I told you about the grow bed media, the grow bed shape, and that you need about one gallon of grow bed/bio filter volume for every gallon of fish tank volume and the reason for this ratio. I discussed the need to flood and drain your grow beds four times an hour and how to properly size your water and air pumps.
In Parts 4 and 5, “System Startup, Operation and Maintenance" I talked about an Aquaponics system's water and all the important aspects of the water like the DO (dissolved oxygen), nitrites, nitrates, pH and alkalinity. I talked about how to measure the water using a freshwater test kit, TDS meter, a DO meter and a pH meter to determine that it’s safe for the fish and the plants. I also explained how to get an Aquaponics system started and how to “cycle” your system.
In Part 6, Ratio of Fish to Water, I talked about how many fish you can place in your system based on a specific and safe ratio; and I said that as a beginning Aquaponics farmer, I recommend you stay at or above 6 gallons of water per pound of fish. Then, I proceeded to give you all the reasons why this is my recommendation.
Now I'm going to discuss Improving Water Quality. Since everything depends on everything else in an AP system, we need to do a little more review. In the previous Aquaponics 101 tutorials, I have put forth an Aquaponics System design. This included a simple set-up of a single fish tank and one or more deep media filled grow beds. This design retains all fish waste in the system and, thereby, allows for (and requires) the mineralization of the fish waste solids in the grow beds, which also serve as bio-filters. Some of the advantages of such a design are low maintenance and operational cost, as well as a minimum number of components required to build the system.
In order for this system to function properly, it must meet certain design criteria. It must have ample bio-filter volume in order to process the delivered fish waste. It must have ample water flow in order to deliver those wastes. It must have ample water aeration in order for the bacteria to process the fish waste. It must have ample grow bed space to grow the plants needed to uptake the produced nutrients. And, it must have ample fish tank volume to hold the fish, which are the engine of the system.
For a simple backyard or school AP system, this is all that is required, as long as it is limited to low fish density, which means having about one pound of fish for every six gallons or more of bio-filter/grow bed. This number can be pushed to one pound of fish for every three gallons of bio-filter; but that borders on the edge of instability. Even if the chemistry measures in the safe range, the lowering of pH due to the nitrification process will always require constant (weekly) adjustment by adding a pH-up solution. As I've shared before, this solution can be either Potassium Hydroxide (potash) or Calcium Hydroxide (lime).
As mentioned above, the system must have ample aeration. This is necessary in order to create a Dissolved Oxygen (DO) content of 6.0 or higher. It will also help to de-gas the water. More on this below. This DO level can be difficult to achieve by just aerating the fish tank, especially if the water temperature is above 78 Fº, because the higher water temperature drives out the Oxygen. Additional aeration can be added to the grow beds; but it adds only a small amount of DO to the system water. This is because the depth of the water in the grow beds is minimal, and the air bubbles don't spend much time in the water. Also, due to the shape of the grow beds, it is difficult to fully aerate them without multiple aeration devices spread throughout their bottoms. Again, this does add some DO to the water but at an equipment and energy cost.
The above photo is of one of our Food Forever™ Growing Systems that we installed in a classroom at Manzo Elementary School in Tucson, AZ. Later, it was placed outside in this Greenhouse. From the looks of their water, we're thinking they're not using Stress Zyme, a product we recommend in Part 5.
This is an FFGS-40 System, which has 44 sq. ft. of growing area spread out among four 11 ft² Grow Beds with a 320 Gallon fish tank.
One of the Manzo Aquaponics Instructors is leaning over the Fish Tank holding a really small fish net. You can follow the progress of the Manzo and the Davis Elementary School Food Forever™ Growing Systems on their facebook page.
Adding additional system components to help improve the water quality is a common practice among commercial aquaculture and AP growers. In the picture above, you can easily tell, even though we have a lot of aeration going in this tank, that our water is quite clear because we have added what we call our WET (Water Enhancement Technology) tank to our system, which I'll explain later. The Tilapia on the left who is out of the bubbles is clearly seeable.
In order to understand these added components, we must first understand what need is being addressed by adding them to the system. Water contains dissolved gasses. In addition to some oxygen in the water, it may contain excesses of Nitrogen, Hydrogen, Methane, CO₂, and Hydrogen Sulfide. Some of these gasses are from the process of fish waste being broken down by the bacteria in the system. Hydrogen, for example, is released into the water when autotrophic bacteria break apart Ammonia (NH₃) into Nitrogen and Hydrogen. They add Oxygen to the Nitrogen to produce Nitrite (NO₂) in its first iteration process and later add more Oxygen to produce Nitrate (NO₃), which is less toxic to the fish than either Ammonia or Nitrite and beneficial to the plants. The released Hydrogen is then combined with the Carbon DiOxide (CO₂) in the water to produce Carbonic Acid (H₂CO₃), which is what causes the water's pH to lower. Carbonic acid is also formed anytime Carbon DiOxide is dissolved in water (CO₂+H₂O-> H₂CO₃). The alkaline buffers that may be present in the water initially will keep the pH high, but they will eventually be overwhelmed by the shear amount of Carbonic Acid being produced as the fish density increases when the fish grow out and are fed more food.
Part of the solution to these troublesome gasses in the water is to de-gasify them in a degassing tank. This is usually a rather shallow tank, which the water flows through as air is being pumped in by way of aerators in the tank's bottom. This degassing operation also adds some aeration to the water.
We have now added two extra components to the system, a mineralizing tank and a degassing tank. And, if we plan on using a deep water culture (DWC) Raft, NFT (Nutrient Film Technique) or Aeroponics (the spraying of nutrient rich water onto the plant roots) instead of deep media grow beds to grow our veggies, then we will need to add another component to the system, the bio-filter. It is interesting to see how little attention is paid to the bio-filter in some of the commercial system designs I've looked at on the internet. The bio-filter contains media with lots of surface area so the Autotrophic bacteria have a place to live and do their thing of converting the Ammonia to Nitrates. The bio-filter is a container of some sort where the mineralized (or filtered) and degassed water passes through the media; and, if properly designed, aeration devices are added to help with the process and to de-gas the Hydrogen.
So, why go to all of this trouble and expense in adding these components? Well, if you are building a low density backyard system, then they are not necessary. But if your system is a larger higher density one, and you want to get serious about growing large amounts of food (vegetables and fish), then improving your water quality not only makes sense, its a requirement.
In a media filled grow bed, the addition of the solid fish waste can be problematic. Even though I have advocated for this being done in order to simplify a small low density home or school system, the grow bed is not the ideal place to mineralize the solid waste. It coats the grow bed media making it less usable for the autotrophic bacteria, which need the media's surface for attachment. It can also coat the vegetable roots preventing them from proper uptake of nutrients. As the amount of solid waste increases, this then becomes a problem.
The project appears to be successful. The air under pressure entering the bottom of the tower and rising degases the water. The smell from the top of the tower is an indication of this process. Distributed over forty four square feet of grow bed, the smell was not noticeable, but the smell coming from the hole in the top of the tower gives an enhanced experience.
The Dissolved Oxygen in the water coming from the overflow back to the fish tanks is at 97% saturation as measured on our trusty Milwaukee DO meter. That is a measured 8.3 ppm (mg/L) out of a possible 8.5 ppm. The DO coming from the grow bed return to the fish tank is 6.5 ppm or greater. The combined DO level as measured in the fish tank is 7.5 ppm. This is quite an improvement from our previous fish tank DO.
The water going to the grow beds is much cleaner than it was prior to incorporating this technology. The fish tanks are becoming even clearer than before.
We have stopped our weekly adding of Heterotrophic bacteria and the water continues to remain clear. This is an indication that the Heterotrophic bacteria is self sustaining. We believe this is due to the high level of dissolved oxygen and our continuous monitoring and adjustment of the pH to keep it very near 7.0.
Over two years of operation and everything still is performing great. We drained the tower in order to move it into a new room we built to separate the fish tanks, filters and tower from the plant growing area as we build out our micro-farm system. We expected a lot of sludge to come out of the bottom of the tower as we drained into the field next door. To our surprise only clean water came out of the tower bottom from the beginning to the completion of the draining process.
This was a welcome discovery and an indication that the mineralization process was working over the two plus years we incorporated the tower into our indoor growing system.
If you're interested in building a Food Forever™ Farm, just email us and we'll send you an NDA to sign. At that point we can share the other component in our cutting edge water cleaning technology in a document we call "How A Food Forever™ Farm Works".
Here it is our WET Tower. It's been in operation for about four years where it started in our growroom that originally had four 11 ft² Deep Media Grow Beds.
In February of 2014, we moved it into our Engine Room pictured on page 29. It's sitting in the near right corner of the room out of the shot.
This is one of the reasons our water is clear enough to grow in the Vertical Lettuce Growing System you saw on page 24.
The other reason is our proprietary Solids Separation BioConversion System, which we also installed into our Engine Room and which is also purposefully out of the shot.
When we moved our WET Tower from one room to the other, we discovered it had been working perfectly as there was no accumulated fish waste in it.
If you are growing lettuce or other leafy greens that can be grown in a DWC raft system. Growing them in media, such as expanded clay, takes more time to both transplant and harvest. In a commercial operation, this added time cuts deep into what little profit margin there may be. By using a raft or other deep water culture (DWC) system, the transplanting and harvesting time is greatly reduced.
In order to use what is called a NFT (Nutrient Film Technique) System or a Raft growing system, the water must be relatively clean, which means free of solid fish waste that might interfere with the plants' uptake by coating their roots. This coating would retard their growth requiring more time and thereby adding cost to the yield. Clean water is especially necessary in Aeroponics, as the sprayers can otherwise become clogged with solid fish waste.
So, how do we accomplish this water quality improvement without adding a lot of system complexity and cost? One way is to combine as many of these operations into as few components as possible. Think vertical. By using a relatively tall tank (which we refer to as a water tower), say six feet or taller, we can take all of the water from the fish tank pump (it must have enough head and flow to reach six feet or more) and pump it into the bottom of this vertical water tower and remove it near it's top. By adding aeration devices in the bottom of the tower, the air takes time to cover the distance to the tower's top, which is vented. On our test tower pictured below, there is an eight inch cap on its very top with a vent hole. We cut a larger hole in this cap and inserted a bulkhead so we could extend the height to prevent water overflow as well as provide a high vent and a place to insert the airline running to the aerators in the bottom of the tower.
About eighteen inches from the tower's top, we added a bulkhead outlet (as far as we could reach into the tower from the top with the cap removed) where the water is allowed to flow from it into the grow beds. This outlet is well above the height of the grow beds and good flow has been achieved. Each grow bed has its own control valve to adjust the flow into it. About one foot above the grow bed outlet and about six to ten inches from the tower's top is another outlet (this, along with the bottom inlet, were built into the original tank) where the excess water being pumped in and not flowing into the grow beds is allowed to overflow back into the fish tank(s).
The slow upward movement of the water allows the heavier than water fish waste solids to precipitate. The air from the air stones placed in the tower's bottom keep the solids suspended. We found that there needs to be a balance in the amount of air that is pushed through the stones; for if there is too much air coming in, then the water becomes less dense and doesn't flow properly from the outlets near the tank's top causing an overflow condition, as well as raising the suspended solids too high. As it turns out, we needed a smaller air pump than we are currently using in the main fish tank.
We sized the tower to contain the same amount of water that is contained in all of the media filled grow beds combined when full. This should be enough volume to mineralize most of the solid fish waste that would otherwise be going into the grow beds.
"This is the last Part of this 7 Part Tutorial on Aquaponics 101, Improving Water Quality.
Get ready to purchase or build one of the most advanced ways to grow food on the planet today using an AP System. Have fun becoming an AP Farmer; and thank you for
participating. Don't forget to Download your Completion Certificate! OLIVER
Many of the Aquaponis growing techniques have been borrowed from Hydroponics, which has been around for a long time.
The picture on the left is a trough growing system, simular to both DWC and NFT. It is a Shallow Water Trough (SWT) system. We have a simular system in our Growroom we call Horizontal Duffy Ducts.
A Really Big Congratulations! You've just completed the final Tutorial of Aquaponics 101, Part 7.
Now it's time to test your knowledge. Take the Part 7 Quiz here:
1. The ______ is the engine of an AP System.
2. The higher water temperature the more it drives out the
______ from your AP System?
3. What are the common dissolved gases contained in water?
4. Which of these gases is released into the water when
autotrophic bacteria break apart Ammonia (NH3)?
5. The released ________ is combined with Carbon DiOxide (CO2)
in the water to produce Carbonic Acid (H2CO3), which causes
the water's ______ to lower.
6. What is one of the solutions to dealing with gasses in the water?
7. When is improving water quality beyond adding Heterotrophic
bacteria a requirement in an AP System?
8. How many extra components did we add to our AP System when
we built our Micro Food Forever™ Farm?
9. What is the name of the Tower we designed?
10. What did we add to the bottom of the Tower that makes it work?
11. The Dissolved Oxygen in the water coming from the overflow of
our Tower back to the fish tanks is at ______% saturation as
measured on our trusty Milwaukee DO meter.
12. The DO coming from our grow bed return to the fish tank is
_____ ppm or greater.
13. What is allowing us to grow vertical walls of lettuce in our
Micro Farm Greenhouse?
You Did It! Your Aquaponics 101 Tutorial is complete. Now you can Download your Completion Certificate and again, Congratulations!
It's been great having you in my Class, Oliver
This is what we call our Engine Room because the fish are the engine of an AP System.
As I explained before, this is not a typical backyard or school system. Our system is demonstrating our commercial sized Food Forever™ Farm Systems in miniature. We do have one 11 sq. ft. Deep Media Grow Bed in the back of this room in this photo.
Our Aquaponics USA website is all about small backyard home and school systems while our Aquaponics World.net website is all about building large-scale systems for commercial growing and for sustainable development in under developed countries.
Notice again how clear the water is because we have added our WET Tower (to be explained below) and our Solids Separation BioConversion System, which is proprietary.