Nitrogen Cycle

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out via both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification. The majority of Earth's atmosphere (approximately 78%) is nitrogen, making it the largest pool of nitrogen. However, atmospheric nitrogen is unavailable for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle.

In a koi pond, ammonia is broken down by naturally occurring bacteria, firstly to nitrite, which is also poisonous to Koi, and ultimately to nitrate. In the quantities we can expect it, nitrate is not directly poisonous to Koi, although it can be a cause of blanket weed. Nitrate can be removed by other means such as a vegetable filter, or a denitrifying filter that employs different bacteria to convert it to gaseous nitrogen and release it to atmosphere. This biological process is referred to as "The Nitrogen Cycle". In reality, the Nitrogen Cycle works throughout the pond, not in the filter alone. All surfaces will support the necessary nitrifying bacteria. A filter, with the provision of large amounts of medium for bacteria to grow upon, ensures that enough biological action takes place to cope with the ammonia produced by the Koi. The 'biomass' (the bacterial colony) will establish itself to the load imposed upon it therefore it is keyed to the stocking level of fish living in the system.

Nitrosomonas bacteria convert ammonia (NH3) to nitrite (NO2)
Nitrobacter bacteria convert nitrite (NO2) to nitrate (NO3)








    When you first introduce fish to a new pond, the main problem is not the solid waste produced by the fish, it is the ammonia(NH3) released into the water. This is very toxic to the fish, especially in a small pond. The first of our friendly bacteria to spring into action are the Nitrosomonas bacteria. These bacteria derive all the energy they need for growth and reproduction from converting ammonia into nitrites. They live in several places such as soil, sewage, fresh water, etc. and they thrive in places where there are high levels of nitrogen compounds. These bacteria need large amounts of energy to divide and multiply and, because of this, it takes a while for them to develop in the pond in such numbers as to be of use. It is, therefore, very important that you do not stock a new pond to capacity immediately when it is initiated.

Once your first fish are put into the system and begin to feed, they will produce toxic ammonia and carbon dioxide (CO2) from their gills and solid waste matter. Ammonia is also introduced into the aquarium by decaying matter such as solid fish waste, uneaten food and dead plant matter. Nitrosomonas bacteria present in the water will begin to convert the ammonia into nitrites (NO2) and, in doing this, will begin to multiply. As the numbers of Nitrosomonas increase and the ammonia levels correspondingly decrease, nitrite levels in the water will rapidly start to increase.

Nitrite is almost as dangerous to fish as ammonia and this is where the second batch of 'friendly' bacteria come into action - the Nitrobacter. These microscopic rod-shaped bacteria begin to colonise the filter and feed on the nitrites (NO2) produced by the Nitrosomonas bacteria. They convert them to nitrates (NO3) which are far less harmful to fish and other animals. In doing this they, too, begin to multiply their numbers until a balance is achieved.
The byproducts, then, of this cycle are the carbon dioxide exhaled by the fish and the nitrates produced by the bacteria. Both of these are used up to some degree by any aquatic plants present. The carbon dioxide is used up by the plants in the action of photosynthesis which produces oxygen back into the water and the nitrates are consumed by the plants as fertilizer to aid their growth.

That is why proper proportions of fish and plants are essential to your pond environment. To give you an idea, a general rule of thumb is that you should have one inch of fish for every square foot of surface area in your pond. 40 – 60 percent of your pond surface should be covered with a mix of marginals as well as floaters. These will not only provide nutrients but will allow your fish some cover from possible predators.

Biofilter

Biofiltration is a pollution control technique using living material to capture and biologically degrade process pollutants. Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, and microbiotic oxidation of contaminants in air.


Water Treatment

Trickling filters have been used to filter water for various end uses for almost two centuries. Biological treatment has been used in Europe to filter surface water for drinking purposes since the early 1900s and is now receiving more interest worldwide. Biological treatment methods are also common in wastewater treatment, aquaculture and greywater recycling as a way to minimize water replacement while increasing water quality.
For drinking water, biological water treatment involves the use of naturally occurring micro-organisms in the surface water to improve water quality. Under optimum conditions, including relatively low turbidity and high oxygen content, the organisms break down material in the water and thus improve water quality. Slow sand filters or carbon filters are used to provide a place on which these micro-organisms grow. These biological treatment systems effectively reduce water-borne diseases, dissolved organic carbon, turbidity and colour in surface water, improving overall water quality.


Use in aquaculture

The use of biofilters are commonly used on closed aquaculture systems, such as recirculating aquaculture systems (RAS). Many designs are used, with different benefits and drawbacks, however the function is the same: reducing water exchanges by converting ammonia to nitrate. Ammonia (NH4+ and NH3) originates from the brachial excretion from the gills of aquatic animals and from the decomposition of organic matter. As ammonia-N is highly toxic, this is converted to a less toxic form of nitrite (by Nitrosomonas sp.) and then to an even less toxic form of nitrate (by Nitrobacter sp.). This "nitrification" process requires oxygen (aerobic conditions), without which the biofilter can crash. Furthermore, as this nitrification cycle produces H+, the pH can decrease which necessitates the use of buffers such as lime.

Differences from goldfish

Goldfish were developed in China more than a thousand years ago by selectively breeding Prussian carp for color mutations. By the Song Dynasty (960 – 1279), yellow, orange, white and red-and-white colorations had been developed. Goldfish (Carassius auratus) and Prussian carp (Carassius gibelio) are now considered different species. Goldfish were introduced to Japan in the 16th century and to Europe in the 17th century. Koi on the other hand, were developed from common carp in Japan in the 1820s. Koi are domesticated common carp (Cyprinus carpio) that are culled  for color, they are not a different species and will revert to the original coloration within a few generations if allowed to breed freely.

In general, goldfish tend to be smaller than koi, and have a greater variety of body shapes, and fin and tail configurations. Koi varieties tend to have a common body shape, but have a greater variety of coloration and color patterns. They also have prominent barbels on the lip. Some goldfish varieties, such as the common goldfish, comet goldfish and shubunkin have body shapes and coloration that are similar to koi, and can be difficult to tell apart from koi when immature. Since goldfish and koi were developed from different species of carp, even though they can interbreed, their offspring are sterile.

Choosing Healthy Koi Fish

So you’ve decided to start raising Japanese koi fish? It’s a great adventure, as koi fish (according to us koi enthusiasts anyway!) are among the most satisfying fish to raise, in that they’re beautiful, and even have personalities, as you’ll see when you’re eventually able to hand feed them.

And koi can live for over 20 years, which means that you can experience their development over a long span of time.

The first step to your koi regime though, is to choose healthy and happy koi.

Choosing wisely when you’re buying koi will help ensure that you won’t be disappointed, and that you’ll end up with an investment that will be worth both the money, and the time and effort.

By the time you finish this article, you’ll know the vital tips on how to properly choose koi for your pond.

1. The first decision to make is to whether you want to buy from your local supplier or through the internet. If you have a local koi supplier, go and have a look at the quality of their koi as well as their facilities. Get an idea of how knowledgeable the owner is about koi in general, but more importantly, about the specific koi that he has in stock.

For example, does he know exactly where they have come from, why he chooses those sources, and how long he’s been using those sources? And does he know the lineage of the fish that he has in stock, about their color characteristics, and the health of this years stock compares to the last?

If there are no local suppliers that meet your satisfaction, then you may have to use an internet supplier or auction.

2. The time of the year to buy your koi. If you want imported Japanese koi, which are the best quality koi usually, then the harvest time in Japan in October and so will arrive in overseas countries in November or December.

A large supplier though, or a supplier who receives stock from the US, or other producers such as Singapore, will have stock at all times of the year, so you can purchase them in any season. If you don’t have a heated pond and you have very cold winters where your pond freezes over, November or December may not be the best time to buy.

3. How long has the koi been quarantined before or after they arrive in the country? Usually one month of quarantine is the minimum, though some illnesses may take longer to develop especially in colder temperatures.

Even if they’ve been quarantined and no diseases are evident, if you have existing koi in your pond, it’s best to isolate the new koi in a separate pond for a month at least before introducing them to prevent diseases from being transmitted to your entire collection.

4. How healthy are the koi? It’s important to look for signs of healthy koi fish.

These are

a) that they’re swimming smoothly and efficiently, and not with any jerking or unsmooth motions

b) that the koi is not damaged in any way, looking carefully at their gills, all their scales, their fins, and quality of their eyes. Ensure that there are no damage, ulcerations, or discoloured spots

c) that they’re not in respiratory distress and that their gills are moving evenly and rhythmically

d) that they’re interacting and socialising well. Koi that swim alone or are hiding in a corner may not be the healthiest or most robust.

If you need a closer look at a koi that you like, ask the owner to hold them up close for you to see.

5. How many koi to buy. A common mistake is to buy too many koi for the size of pond, or to put it the other way around, to have too small a pond to begin with. Especially with the Japanese koi, that have the largest growth potential, they can grow to over 2 feet (60 – 70cm) in length, and thus a sufficient volume of water and filtering system is required to keep the water clean and oxygenated.

Generally, you should have 1000L of water for each koi, especially with the Japanese variety. Plus, your pond should be ready before you go buy the koi.

If this is your first ever koi pond, and you’re looking at top of the range koi, it may be wise to not buy your entire stock of expensive koi at once.

It may be wiser to buy a few to test everything out, to make sure that the pond set up that you’ve got is producing good results.

If going for a $10 to $20 koi, then many will be able to afford the whole new family at once.

So there you have it, your first piece of the puzzle when it comes to keeping koi.

You’ve gotten some tips on choosing koi for your pond to help you to maximise your results with this enticing and very rewarding hobby.

Keep learning, especially about koi care and koi pond set ups as well.

Here’s good feng shui to you and your new koi family.

How Often Do You Feed Koi Fry?

When your koi fry hatch from the eggs, they will immediately attach themselves to any surface and continue to feed on their yolk sac until it is consumed. Then, the fry will rise to the surface to gulp some air and get their swim bladders working. After that, the fry will swim around in search for food.

Some experts do not advise giving your koi fry dry or artificial food for at least 6 to 8 weeks as it (artificial food) can damage the newly developed gills and will likely pollute the pond water. What they also want to avoid is the buildup of ammonia or nitrite that can quickly kill the fry. So how often do you feed koi fry? Experts recommend providing the fry with an ample supply of live, natural food like daphnia and infusoria to ensure their survival and fast growth. To produce daphnia and infusoria, you need to prepare your growing on pond a month before spawning by seeding it with chicken manure or use leaf mould if you are afraid that the manure might contain salmonella.

Still, there are keepers who feed the koi fry with boiled egg yolk during the first few days in order to increase the size of the stomach. You can also give koi fry newly hatched brine shrimp after a week. Then, you may start them on a mash diet – the fine powder ground from high protein koi food. Do give your fry some spirulina and pure wheat germ too. Feed the fry small amounts but often, about four to five times a day during the first three months. As the fry start to grow, you can feed them less often, about three times a day until you can introduce them to a regular diet of koi food, beginning with smaller pellets and gradually increasing the size of pellets until they can also eat what the adults eat.