Over the years, koi have become a popular choice of fish for many with an interest in aquaponics. They thrive under conditions favoured by plants and have a great following in the UK and rest of the world. Not many koi keepers however, will have heard of aquaponics. This is a shame as there are real connections between aquaculture, koi keeping and horticulture. They have much in common and there is much to learn from each other but what is aquaponics? This article outlines a few areas where the application fo aquaponics could offer some interesting benefits for koi keepers.
Aquaponics is basically the combination of aquaculture and hydroponics. Aquaculture is the rearing of aquatic animals and hydroponics is the soilless production of plants. In short;
Aquaponics = Aquaculture + Hydroponics
Aquaponic advantages for koi keepers
More specifically, potential advantages of an aquaponic system gained by koi keepers include;
- Removal of nitrates
- Improved algal control
- Production of plants that can be fed back to the koi – or the family!
- Fewer water changes due to better water quality
- Lower filter maintenance as no cleaning required
- Lower capital cost of filters
Improved water quality
It is well recognised that nitrates are considerably less toxic to koi than fish ammonia. A fact that underpins the value of including a biofilter. It must, on the other hand, be better to remove nitrate than allow it to perpetually accumulate. Aquaponics represent a relatively straight foward method of reversing this accumulation. Incidentally, high nitrates may also adversely affect the colour pigmentation of certain koi varieties. It is, without question, better to keep nitrate levels relatively low.
Better water quality , and the subsequent need for less water changes, is always desirable. Less water input raises the possibility of running a koi pond at a lower level of hardness if a suitable pre-treatment system is adopted. This is more in keeping with the conditions that exist in Japanese koi ponds.
Plant production is usually the dominant concern for most people who operate aquaponic systems. Fish production is often, but not always, a secondary concern. As the drive towards commercial aquaponics continues I’m sure this situation will change. Aquaculture, in particular recirculating aquaculture systems (RAS) continue to evolve and have a greater role in the development of this rapidly expanding industry.
Plant filters are nothing new to koi keepers. They are still loved by many and offer similar advantages as is offered by aquaponics. Also, plants are generally more attractive than koi filters. ( A fact well worth stating when discussing the size of the next pond with ‘the Boss’). Water gardens can be beautiful and offer endless opportunities for creating stunning designs. Of course, you could take a leaf out of the aquaponic practitioners book and grow some wonderful fresh, organic and tasty fruit and veg for the family. More likely, you would want to grow some fresh organic veg to feed to you koi. The production of lettuce, water cress and even duckweed is ideally suited to an aquaponic system and all of these make a very welcome addition to the diet.. You really would be making the best of the nitrogen cycle.
How aquaponics works
So how does an aquaponic system work and how does it differ to a typical koi pond. The first thing to note is a grow bed, this is where the biofiltration occurs and the plants are rooted, is usually much bigger than the fish holding tank. Koi ponds tend to be the other way around. However, too big a filter is seldom a problem for koi keepers. This is not the case in aquaponics. If there are not enough fish to supply the plants with sufficient nutrients they will not thrive. The fish, the biofilter and the plants all need to be in balance with each other. In a koi pond it is just the koi and the biofilter.
There are a number of different growing systems in aquaponics but the grow bed filled with media such as expanded clay balls is the simplest and most popular. It combines both suspended solids removal and ammonia breakdown in the same container. Something perfectly possible if the filter is large enough to allow effective donation of the different bacterial groups involved. The relatively low capital costs involved means that larger is not normally a problem.
The bell syphon magic
There is a ‘secret ingredient’ that makes this happen. The item in question is the bell syphon. Something that most koi keepers have never heard of. During normal operation an aquaponic system involves the constant pumping of fish water into the grow beds. The bell syphon sits in the grow bed and triggers the water to automatically drain into a sump once the water level approaches the top. Once the water has dropped to a low level air enters and therefore stops the syphon. Thus there is a continuous raising and lowering of the water level within the grow bed. This is generally referred to as a ‘flood and drain’ system.
This allows an excellent distribution of oxygen and nutrients throughout the grow bed and is critical for success. It is therefore, easy to meet the high demands of the breakdown of fish solids. The bell syphon is a simple and cheap device that does not even require a power supply. In effect the grow bed is a cross between a submerged filter and a trickle filter.
Summary – Top 10 benefits
The following are some of the potential benefits that an aquaponic system could offer koi keepers.
- Better water quality by the effective removal of nitrates
- A reduction in nutrients reduces excessive algal growth
- Better oxygenation of the biofilter by the use of the bell syphon.
- No filter cleaning required
- The production of high quality organic plants that can enhance the diet of you koi, or that of you family
- Easier to make the biofilter an attractive addition to the garden
- Effective combined removal of solid and dissolved fish waste within the same filter.
- Fewer water changes
- Easier to pretreat incoming water as volume is less
- Filter media and grow bed container considerably cheaper than most koi filters.