Aquaponics Journal

Nelson and Pade, Inc.® began publishing the Aquaponics Journal® in 1997 and continuously published it through the beginning of 2013. There are a total of 62 issues, all of which are available as downloadable PDF files. The Aquaponics Journal® is the original publication covering aquaponics technology, information, research and events. It has chronicled the start and growth of the aquaponics industry and has now become an online news source for anyone looking to expand their knowledge of aquaponics.

The new online version of the Aquaponics Journal® is available to everyone, to enrich their knowledge of aquaponics and to help educate and assist people in getting started and being successful in aquaponics. Check back often!

Aquaponics Journal

The Success Package saves you money on the services and training that will get you up and operating your commercial aquaponics venture successfully. The Extended Stay Learning  Program, our Dry-Fit Assembly Assistance and the Nelson and Pade Grower Program provide you with the training, technical support and guidance you need to get started and become successful in commercial aquaponic farming. The Success Package makes these services available at a discount at the time you make the system purchase.

A client recently asked us to explain the difference between nitrification and mineralization, two very important processes in aquaponics.  Nitrification is essential for fish health, because it converts ammonia to nitrite and then nitrite to nitrate.  Both ammonia and nitrite are toxic to fish at low levels, so there is a great deal of discussion about nitrification related to keeping fish healthy.  Nitrification also generates the nitrogen our plants need to grow.  Mineralization is critical in aquaponics because it is the process in which all of the other minerals are generated from the fish waste.

Nitrification and mineralization are two separate processes. Nitrification is the oxidation (conversion) of ammonia to nitrite to nitrate.  It is only done by nitrifying bacteria (nitrosomonas and nitrobacter) in aerobic conditions.  Nitrification happens throughout the system, on all surface areas and in the water column.  In our Clear Flow Aquaponic Systems®, we provide very specific habitat for the nitrifying bacteria to live and thrive.  Nitrification decreases alkalinity and pH because the process naturally produces nitric acid.  The nitrogen for plant growth comes from nitrification.

There is a converse process happening called de-nitrification, which reduces overall nitrogen levels. De-nitrification happens in anaerobic conditions. In our systems, we allow de-nitrification to happen in the mineralization tanks. As pockets of material build up, de-nitrification begins to occur, resulting in an increase of alkalinity and an off gas of nitrogen gas. The amount of de-nitrification you allow to occur will directly affect the amount of nitrogen you have in relation to all other elements.  When growing vegetative plants, you want a higher ratio of nitrogen, so you can clean the netting more frequently.  When growing fruiting plants, you want a lower ratio of nitrogen so you clean the netting less frequently.

We use de-nitrification to our advantage, as needed, to maintain the ratio of nitrogen to other elements in the range that is most appropriate for the types of crops we are growing.

Mineralization is the breakdown of organic matter into individual elements (macro nutrients like potassium, calcium, sulfate, phosphorous, magnesium and micro nutrients like iron, copper, molybdenum, zinc, etc). Mineralization is done by heterotrophic bacteria in anaerobic conditions.  In our Clear Flow Aquaponic Systems®, the netting in the mineralization tank serves as a means of collection of the fine suspended solids.   We do not aerate this tank to encourage heterotrophic bacteria to thrive and break down the solids into all of the elements the plants need. The dwell time in that tank gives the heterotrophs time to break down the solids.  What is released are the actual elements (minerals) that the plants need.

Both nitrifying and heterotrophic bacteria exist everywhere and do these same processes whether in the water or soil.

heather-in-greenhouseOne of the many benefits of aquaponics is that there is no back breaking labor and no dirt to deal with.  So, what is there to do?  An aquaponic system isn’t difficult to maintain but there are daily and periodic tasks that must be done to ensure a healthy system.

Fish Feeding
The availability of dry, species-specific fish food is quite common, a result of the rapidly growing aquaculture industry. Today’s specialized fish feeds provide precise amounts of protein, carbohydrates, fats, vitamins, amino acids and minerals. In a hobby or ornamental system it is fine to feed your fish only once a day. If food production is your goal, you’ll want to maximize your efforts and feed more frequently.  Most commercial growers will feed three times per day.  Feeding by hand gives you the opportunity to observe the fish and their feeding habits.  You can also use timed mechanical feeders or use an on-demand feeder so the fish can eat whenever they are hungry.

Plant Seeding, Rotation and Harvesting
When growing leafy crops that quickly mature, such as lettuce and herbs, you should plant frequently so you are assured of a continual harvest.  With leafy crops, when you havest, you seed and transplant the same number of plants you harvest.  This will provide continuous harvests, 365 days per year.

Seeds for an aquaponic system are usually germinated in a small rockwool cube or in a container of loose perlite, vermiculite, a seedling mix or coco coir. Germination can be done within the aquaponic system or in a separate area designed to provide proper environmental conditions for germination. Once the seed has germinated and a seedling has developed, the small plant is transplanted into the plant growing bed.

Observation and Monitoring
Every day you should visually inspect the fish and the system. Make sure the water is flowing properly, the aeration system is working and the drains are free of debris. Watch to see that the fish eat vigorously and swim normally. Look for problems such as fungus, open soars, torn fins or discoloration and check the temperature and pH of the water. Observe the plants for pests and insects. Remove any dead plant matter.

Fish Harvesting
In a home food production system, you will most likely harvest fish as you want them, once they’ve matured. Commercial operations will harvest based on market demand and production. Farm raised fish always taste the best if they’ve been purged for several days prior to harvesting. Ideally, the fish should be removed from the main system and held without feed for several days prior to harvest.

Water Quality Testing
Anyone serious about aquaponics should invest in a water test kit, which will enable you to measure and keep track of pH, ammonia, nitrite, nitrate, dissolved oxygen, alkalinity and water hardness. Most kits sold are easy to use and are based on color changes in the sample being tested. Meters that measure dissolved oxygen, temperature and other factors are also available.

Cleaning Filters and System
The key to a healthy system is keeping it clean, removing any dead or unhealthy plants or fish. Filter tanks such as a clarifier required periodic maintenance.

Successful Operation
How successful you will be in operating an aquaponic system is directly related to how well it is designed.  Starting with a proven system design will result in consistent results and trouble-free operation.  Success in aquaponics also comes from being organized, efficient and focused on the health of the system as a whole.

Watch “A Day in the Life of an Aquaponics Grower” Video

Absolutely!  UW-Stevens Point’s Continuing Education program, Department of Biology and Northern Aquaculture Demonstration Facility have partnered with Nelson and Pade Inc. to offer a full semester course, Introduction to Aquaponics.  It is available as either a two credit or three credit course.  All lectures and discussions take place online.  The three credit option includes a 3-day lab session at Nelson and Pade, Inc.’s demonstration greenhouse in Montello, WI.

Course Content – The lectures run from late February – early May and take place online, each with a self-study session followed by a live chat with one of the three instructors. The hands-on lab sessions for the three credit course are held in May at Nelson and Pade Inc.’s demonstration greenhouse in Montello, WI. The course covers an introduction to and history of aquaponics, applications and benefits, system components, water quality dynamics, environmental control, plant crop choices and plant biology, fish selection and fish biology, integrated pest management and biosecurity, daily operation and record keeping, good agricultural practices, economics of aquaponics and marketing.

Open to All – Students from Around the World – The course is open to students at UWSP as well as students from other colleges and universities anywhere in the world, through UWSP Continuing Education. Registration is through UWSP Continuing Education Office.

Registration is open for Spring 2014 Semester!  Seats are limited.  Register here:

Feel free to visit the following web pages to learn more about aquaponics:

I recently read a reference about our systems on an aquaponics gardening forum and the author of the post inaccurately implied that we were misrepresenting how much fish we can raise in our multi-tank systems. This post demonstrated a total lack of understanding of staggered stocking and multi-tank systems. Given that the person writing the post runs the forum, and can delete posts that are in conflict with hers, I don’t have a means of replying directly to that group.  But, it made me realize that the concept of staggered stocking is a great topic for this Q and A column.

The reason all (except for our smallest hobby system) of our Clear Flow Aquaponic Systems® use multiple fish tanks is so that a grower can use staggered stocking to increase fish production and, therefore, increase the nutrient load to grown more plants.  In staggered stocking, you have multiple fish tanks and stock them sequentially.  The fish are stocked at a given size, typically 50 grams and then grow to maturity in that same tank, along with those same fish that are growing at the same rate.

Let me give you an example. We will assume you are raising tilapia in our Family Plus system, which has 4 100-gallon fish tanks, along with the proper filter tanks for converting fish waste to nutrients and raft tanks for plant growth.  First, let’s look at the growth rate of tilapia.  With proper feed rates, quality feed and good water quality, it takes 24-26 weeks to raise a tilapia from 50 grams to about 600 grams (1.5 lbs.), which is the size most growers harvest at.

When starting your system, you initially stock one tank with about 38 – 50 gram fingerlings.  Then, 6 weeks later, you stock the second tank with the same number of 50 gram fingerlings.  And, every 6 weeks, you repeat this in the remaining tanks.  After 24-26 weeks from the date you stocked your first tank, and every 6 weeks after that, you will have a tank full of fish ready to harvest.  When you harvest a tank, then you restock it with 38 – 50 gram fingerlings.

This means that in each fish tank in the system, you will raise 2 full crops of fish, one every 24-26 weeks.  So, if you harvest 38 1.5 lb fish (57.5 lbs) from each tank twice a year, you will annually harvest 460 lbs. from the Family Plus system.  The real beauty of this staggered stocking is that you never have more than one tank ready for harvest and, with sequentially smaller fish in each tank, you are never over the system capacity and have a steady supply of nutrients for the plants.

The density of the fish in the tank ready for harvest is 1/2 lb of fish per gallon of water.  But, if you look at the total water volume of our systems, you are actually raising fish at a density of one twelfth lb of fish per gallon of water.  This is a much safer ratio than any other method of stocking that I know of.

And, there are other benefits which include better nutrition and less stress for the fish. With staggered stocking you can get the right feed to the fish at each stage of growth.  With a mixed size population in one fish tank, it is impossible to make sure the fish are eating the right sized pellet and getting the right nutrition for the stage of growth they are at.

When you have a tank of fish ready for harvest, you can net those fish out of that tank.  If you have a mixed size population in one tank, you stress all of the fish when you are trying to net just the big ones.

So, all in all, when you compare using 4 – 100 gallon fish tanks  to using 1 – 400 gallon fish tank, you can easily see the value of the four tank system.  When you apply this to our larger systems that use 6 fish tanks, your output is every 4 weeks.  And, if you install two of these modules, your harvest of fish is every 2 weeks.  With three modules, the harvest is every 1 week, and so on.  From both a production and marketing point of view, this method is far superior to a single fish tank aquaponic system.

All of our Clear Flow Aquaponic Systems® use the same multi-tank design and have the same volume ratios, water flow dynamics and components. We do that so someone who starts with one of our hobby system is using and learning a design that is scalable to commercial production.

You can see the concept of staggered stocking demonstrated in our commerical greenhouse, on tours or in our training programs.

Prior to adding fish to your system, it is important to go through an acclimation process. This makes it less stressful for the fish while providing you a greater level of bio-security. The goal of the acclimation process is to ensure that your fish are healthy and free of disease and to reduce the stress of the move and new water quality conditions.

Since you want to avoid fish disease and parasites in your system, be sure to start with a quality source of fish that you are confident is healthy.  Responsible fish suppliers can provide a fish health certificate and will demonstrate to you that they have strict bio-security protocol within their facility.  Even with the knowledge that you have an excellent supplier, you still need to inspect the fish upon arrival, prior to bringing them into your facility, and to acclimate them to your water quality.

Once you’ve inspected the fish and are confident that there are no obvious health issues, bring them into the facility and begin the acclimation process.  Many growers add the step of quarantining the incoming fish in a separate system prior to introducing them into the aquaponic system.  Either way, the acclimation process needs to be done.  Essentially, you want to acclimate them to your water by adding small amounts of your system water to the bag or container the incoming fish are in.  This results in a slow dilution of the water from the supplier as you add your water.  As more and more of your water is added, the fish are slowly acclimated to your pH, temperature and other water quality factors.  Once you have diluted enough so the pH in the bag matches that of your water, you can gently net the fish from the bag and place them in your tank.  Do not add the water from the bag to your system water, or you could be inadvertently be adding snails, parasites or bacteria that could be harmful.

Since you can’t use pesticides in aquaponics, you need to be vigilant in your pest scouting efforts and quick to react if you see any pest problems.  Pest control in aquaponics is really about prevention through good management practices such as writing and following a bio-security program, regularly monitoring and scouting for pest insects, keeping weeds and debris from growing around the outside periment of the greenhouses, installing proper insect screening on greenhouse openings and keeping the greenhouse clean and free of dirt and dead or dying plant material.

In over 20 years of operating commercial hydroponic and aquaponic greenhouses and consulting in the same field, I consistently see that the growers who keep their greenhouses clean and crops healthy rarely experience any pest problems.  Plant debris and unhealthy plants attract pest insects.  Healthy plants repel pest insects.

If you do discover pest insects in the greenhouse, don’t panic. There are natural ways to control them.  First, though, you need to properly identify the pest and then determine what the biological control is.  Most often, this will be another insect that is either a predator or parasite to the pest insect.  A predator, like the lacewing shown to above, eats the pest insect.  A parasite will disrupt the life cycle of the pest insect.

At the same time you are ordering beneficial insects, physically remove the affected plants along with the pest insects as best you can. When the beneficial insects arrive, distribute as directed by the supplier and let them do their thing.  Biological pest control is a fascinating and effective means of controlling pests when you are in a well-constructed, controlled environment greenhouse.

The ROI on an aquaponic business venture depends partly on the investment made and equipment chosen, combined with good management practices and marketing skills.  The other part of the formula to success is to work with a company that has more than a couple of year’s experience in aquaponics, a company that can actually provide the follow up, support, information and assistance you will need as you learn how to operate the system. For example, just last week we got another call from a very upset Aquaponics enthusiast who was asking us for advice on how to fix a system that one of our “competitors” sold to her, yet would not support.

Just for clarification, a Return On Investment is a percentage — the annual income a system produces divided by the money invested in that system.  We provide both of these financial models and many others to our clients once we know their parameters and we are in the process of Project Planning

I know there are some start-ups in this industry that think they can produce an ROI out of thin air, but it is absolutely impossible to provide a simple formula for Return On Investment without knowing a great deal more about your startup venture in aquaponics.  Some of the variables in determining ROI include the initial costs of equipment and infrastructure, construction and installation costs, local contractors and permitting costs, climate, market and local labor costs, marketing methods (wholesale vs. retail), energy costs, crop choices, etc.

Unlike some of our contemporaries in this industry, I will not tell you anything you want to hear to get you to buy something from us. That just isn’t how our company operates.  We believe that success breeds success. So, we are honest about the potential and return and we work very hard to make sure our customers get off to a great start and become successful.

We have been in the controlled environment agriculture and the hydroponic and aquaponic business for over 20 years providing proven systems and reliable information to schools, individuals and businesses.

We look forward to the opportunity to provide you with accurate and helpful information on aquaponic growing.

I am always surprised when people don’t find the domain   Our company has been on the first page (and for most of it, #1) of all search engines when searching for “aquaponics” since 1997.  Our company has been involved in aquaponics since before the internet was invented, researching, developing systems, teaching, working with the leading research scientists and refining aquaponics.  There was a time when people seeking information would consult learned individuals, qualified authorities who wrote books, university libraries, and even attend conferences.  I am always shocked when I find people who ignore the literary content of the internet, which was initially developed to share university literature and research, yet believe blogs written by amateurs and videos shot in someone’s backyard are accurate.

I am glad you found our website and company. Since you are somewhat new to aquaponics, one way to learn more would be to study our website thoroughly. There is a great deal of information.  You should also consider attending one of our 3 day Aquaponics Master Classes to get a good understanding of how our systems work and the production capability they have.  As you may have found there is no end to the websites on the internet promoting aquaponics.  Most of them have no history to their company that goes further back than the day they “discovered” aquaponics.  Even worse many have cleverly used modern marketing techniques as a substitute for substance.  Many of them became “consultants” after attending their very first workshop on aquaponics.  If you look at our company’s history, you will see what sets us apart.

We have been in the controlled environment agriculture, hydroponic and aquaponics business for over 25 years.  We have been working with the research scientists who, over the past 20 years, developed the science of aquaponics. Our company has advanced this science to a point where it is a viable industry so that this method of food production can be profitable while contributing to the ability to grow high quality, safe, nutritious food locally.

Not only do we offer complete science based growing systems and greenhouses that meet your local environmental conditions necessary for proper plant growth but we also offer the training, follow up technical support and expertise to create a bio-secure program that assures your consumers that the produce is safe and nutritious. Rebecca Nelson has also written a great book on aquaponics food production and that is the name of it.  You will find it on the “shop” section of our website.