Advantages and Disadvantages of Aquaponics

Advantages and Disadvantages of Aquaponics

 

posted Feb 6, 2011, 10:17 AM by Matthew McCarthy   [ updated Feb 6, 2011, 2:27 PM ]

We covered this briefly during the early part of our research phase but I though it would be good to provide some additional detail and opinion now that we have researched aquaponics in greater depth and have some personel experience.  It is obvious (from looking through this site) that I have a bais in favour of aquaponics (we have invested significant time, energy and money in aquaponics) though I have attempted to set this aside and provide an unbiased assessment of some of the claimed advantages and disadvantages. The purpose of this post is is to determine if there is evidence to support the commonly made claims found on forums and wedsites (and as important some of the perceived claims) and where there isn't to provide an opinion based on our experience and/or the information available.

The emphasis of this list is a discussion relating to back yard systems rather then commercial systems.

Advantages and Disadvantages of Aquaponics

Claimed Advantages Aquaponics

1. Significant reduction in the usage of water (compared to traditional soil methods of growing plants) as all water is recycled through the system and it is not necessary to discard or change any water (under normal conditions). It has been reported on various forums and websites that water usage is around 90% lower then traditional soil gardening.  I have not seen in any of my research any detailed documentation of experiments/monitoring of both aquaponics and soil gardening side-by-side; so I would say that this a 90% reduction is probably anecdotal. With our system I have added water once since the middle of December (approximately 6 weeks ago) and I would estimate the water level had dropped by between 10% and 20% of the tank height over this period and that 70-140l of water was added to the system. This is equivalent to water usage of 2-3 litres of water a day - much less then I expect would be required in a similar soil based garden.
2. Growth of plants is significantly faster then traditional methods using soil. Again I haven't found any documentation of detailed monitoring of side-by-side gardening. I imagine any time differential between the two methods would be dependent on how well each method is carried out. In aquaponics the plant roots are watered (flooded) at least once an hour in most system and have constant access to high levels of nitrates that are in the water. Though soil gardens can be set up to provide good levels of water and the required nutrients. Perhaps specific plants will grow better in soil and others in aquaponics?
3. Aquaponics grown vegetables are bigger and healthier then when grown in soil. Certainly the pictures and videos I have seen show aquaponics systems that look remarkably prosperous with big, vibrant and healthy fruit and vegetables. There is no indication that the same could not be produced in a well managed soil garden. 
4. There is no need to use artificial fertilizer to feed the plants. In the perfect system this is probably true though some aquaponics owners add "supplements" such as iron to their system to compensate for non-ideal environments (e.g. high pH systems). Fertilizer in the traditional sense is not used and indeed using fertilizer would likely harm or kill the fish. So there is probably a real cost saving over soil gardening in this area as there is no need  to be improve soil before planting or during plant growth.
5. There is no need to dispose of fish waste or provide an artificial filtration system. In land based aquaculture systems either water needs to be replaced or some filtration needs to be provided to remove ammonia (fish waste) from the water. Filtration needs to be provided for the same reasons in aquaponics systems - though in a lot of systems the filtration serves as the medium to grow the plants and the plants remove the (less toxic to fish) nitrates from the system.
6. Significant reduction in land is required to grow the same crops as traditional soil methods. I believe this is true though again I haven't seen concrete evidence to support this claim. As water and nutrients are constantly provided it should be possible to grow plants close together with the main requirements for spacing being access to light.
7. It's easier to setup for year round use compared to traditional gardening methods as grow beds are raised of the ground and growing area is compact allowing for economical "green house" type methods to be employed. I guess this would be true in very cold climates where the ground freezes in winter though in many climates using ground temperatures can help to moderate the temperature of water/media in the system.
8. It's organic. I guess if the fish are fed organic feed and food grade plastics are used then this could be the case. Though there seems to be little good evidence (and I haven't done an extensive search) to show that non-organic crops are necessarily unsafe or less healthy then organic ones.
9. Commercial setups have been used as tourist attractors in rural communities to provide and additional revenue source. I haven't really looked into this but I know that in some areas agro-tourism is used to supplement commercial incomes. Less likely to meaningful in a back yard setting.
10. Yummy - fish for dinner every night! I don't think this is an actual claim that any backyard aquaponics owner would make but it is certainly the impression that people have when they first hear about aquaponics. In fact, somewhere in the order of 90% of the produce from an aquaponics system will be from the plants - so unless you have a very large system you will be more likely to be eating fish once a week or once a month.
11. Reduced damage from pests and disease. I don't know if this is an actual claim many or any people make but I have noticed that there is a lot less leaf damage on my plants this year (grown via aquaponics) then my soil based plants last year. I should note that we are growing different vegetables this year to last and the tomatoes are yet to fruit. Many aquaponics system owners do have problems with pests and as there are fewer options available to control pests (i.e. pesticides can not be used as they could harm or kill the fish) some plant damage is accepted.
12. No weeding or bending down on the ground required. Many backyard systems are setup so that the grow beds are at waist height (to allow gravity return of water to the fish tank) so this allows for a pleasant way to inspect and harvest the plants. This does not have to be the case as there are many different system designs. To my knowledge and from our experience weeds do not grow in aquaponics systems. Inaddition the system pretty much looks after itself - it waters itself and once established provides a great environment for both fish and plants to grow. There is occasional (once or twice a month) maintenance required in cleaning the fish tank with a broom and checking and cleaning the pumps.

Claimed Disadvantages Aquaponics

1. Can be expensive to setup as the system requires pumps, tubing, and tanks/beds. This is certainly true though it doesn't necessarily need to be. A small backyard system purchased complete from an aquaponics retailer can cost over $2,000 installed and the larger backyard systems capable of feeding a family between $5,000 and $10,000. Though if you are willing to devote some (or a lot) of your own time and energy then I think similar systems could be built for 25-50% of these costs (this is my guestimate). Grow beds and fish tanks can often be obtained for free (in western countries) and gravel obtained from the local river, though components such as pumps and backup power supplies will still need to be purchased. System purchase sosts have obtained from this source: http://www.backyardaquaponics.com/Travis/CostBenefitAnalysisofAquaponicSystems.pdf
2. You need a green house to really have a good aquaponics system. I guess this depends on what type of climate you live in. A green house can be advantageous to provide heat in cold winters, protect the system from heavy rains and keep out pests. This is also true for soil based gardening.
3. Setup requires technical knowledge of aquaponics systems and hence is possible to make mistakes. True - there are stories around of people who loose fish and give up on their aquaponics system early on and there is some knowledge required to establish the necessary bacteria within the system. In a lot of cases these failures are because systems have fish stocking rates that are to high. We have yet to stock our system with fish so I can not provide a lot of information from our personal experiences though the initial establishing of bacteria (known as cycling the system) was very simple and took a lot less time then the average system cycling time.
4. Water needs to be constantly monitored to make sure the water quality is OK for fish. This is certainly the case during the first couple of months. After the system has matured water testing is usually carried out only once a week unless there are problems. 
5. Seems very complicated for the amount of fish I will get. Yes keeping a healthy environment for the fish is where most of the complexity lies within the system. Water needs to be free of toxins (especially ammonia and nitrite) and also have enough oxygen for the fish you are keeping. This can involve adding extra aeration sources and making partial water changes to improve water quality.  Stocking fish at a lower density will in most cases reduce the pressures on a system and make it more tolerant to changing conditions and less likely to suffer from the above problems - though this means you will have less fish to eat.
6. Aquaponics requires electric energy input to maintain and recycle water within the system. In most cases you will need to provide electricity to run a water pump and possibly aeration pumps as well. We run our 80w water pump for 5 minutes every hour to flood and drain our three grow bed buckets. As we currently run the pump day and night this amounts to 2 hours of usage a day - so similar to having a light in your house (with an old style bulb) on for the same length of time. We plan to add another three grow beds to the system so this will increase our electricity usage further. At this stage we have not made any attempt to optimize the flood/drain cycle so there may be opportunities to reduce the number of times the system is flooded each hour or to not run the system at night with little impact to plant growth. 
7. If one or more components fail this could lead to the loss of fish and or plants. In this regard you are dependent on using reliable technology (and back up systems) to ensure that your fish, which require oxygen in the water, remain alive an healthy. Your plants are likely to be unaffected in the short term, as the growing medium will likely retain more then enough moisture, though if the fish are not provided enough oxygen, they can suffer and die. This is the same situation for aquaculture systems.
8. You can't grow root crops. You can grow pretty much anything in an aquaponics system from fruit trees to root crops, though depending on the type of growing medium potatoes and carrots may grow into some weird shapes. Most people focus on growing leafy vegetables.
9. Ok so you don't have to add fertilizer or nutrients but you do have to provide fish food. Yes you do, the fish eat the food and their waste is used to produce nutrients for the plants. Of course you also have to feed fish in an aquaculture system and in an aquaculture system fish waste is not used in such a productive way. Fish are some of the best animals at converting food into body mass (different fish species vary) and so are an efficient way of producing meat and protein. Most people buy commercially available fish food for their fish although many people supplement this feed by growing worms, duckweed and other plants and animals. 

Conclusions

It seems that a lot of claims are made based on personal experiences which is not surprising as it appears that very little research has been carried out in this area or in the field of the best aquaponics practices. Most claims (in regards to both advantages and disadvantages) have some truth to them, though in many cases these seem to be littered with over generalizations and are largely based on what has or hasn't worked for an individual.

So is aquaponics the best way to garden? It does produce very good results but are they better then soil based gardening? Well that probably depends to a large extent on where you live and the type of climate you have. If you live in drought effected areas (as much of Australia has experienced over the last decade) then I believe there could be some significant benefits using aquaponics to reduce water usage. Also if you have a limited space to grow vegetables then it is possible that aquaponics could allow you to grow more produce and make the best use of your vertical space. These I think are the distinct advantages to aquaponics; after these the advantages become a little more cloudy and, compared to soil based gardening, the disadvantages start to balance the advantages that aquaponics has to offer.

So why haven't I talked up the fish element of aquaponics. Well for starters we don't have any fish at the moment in our system and have been using aged human urine as our ammonia source (though we do intend to get some fish soon). In aquaponics and small aquaponics systems in particular it seems like the fish should be considered as a nice by-product rather then a primary produce. In a system such as ours (i.e. small with less then 20 fish) the fish are primarily there to provide an ammonia source rather then for the quantity of fish that will be eaten. In addition keeping fish is the riskiest and most complicated part of the system, so if looked at from that very narrow perspective, keeping fish provides a relatively high risk for little gain (in terms of produce). In larger systems it is possible that the fish produced would be considered an distinct advantage but in most systems they seem to simply be the "cream" on top of the fruit and vegetables produced. 

Our system is still young; for me the biggest advantages have been working as part of our small team to design and build a system that appears to be strange and that most people are amazed when they see it and understand how it works. Also being able to sit back and watch the plants grow (and recently explode) has been particularly satisfying. We had our first green salad from the garden last night, which was great, but for me success (or at least proof of concept) will be when we get to eat some of the beans and tomatoes that are currently growing.

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