Know your water enemy

Know your water enemy

The conversion of ammonia to nitrate is actually a two step process carried out by two different classes of bacteria. The first stage is the oxidation of ammonia (NH3) into nitrite (NO2-) by nitrosifying bacteria including species of Nitrosomonas, nitrosococcus, and Nitrosospira. 

The second stage is the oxidation of nitrate to nitrate (NO3-̊ , in this case by nitrifying bacteria, primarily species of Nitrospira rather than the Nitrobacter species often mentioned in older aquarium books.

These bacteria use ammonia and nitrite as a source of energy, oxidising them to release energy the bacteria use to synthesise their food. It is essentially a similar process to photosynthesis, where plants use light energy to synthesise food, except in this case the bacteria are using chemical “fuel” instead of sunlight.

New tank syndrome occurs whenever the filter is not yet fully colonised by sufficient nitrosifying and nitrifying bacteria to deal with the waste produced by the fish in the tank. It isn’t exclusively a problem with new tanks, despite the name. every time you add new fish to a tank, the tanks enter another period of new tank syndrome while the filter bacteria multiply up to deal with increased amounts of fish waste. 

Cleaning the filter media too harshly or careless use of anti-microbial medications will knock back the populations of bacteria as well, setting your aquarium up for another round of new tank syndrome.  

The symptoms

Fish react to new tank syndrome in remarkably consistent ways. Initially, they adopt stress colouration, and behave nervously without showing much interest in food. Air-breathing fish such as gouramis and cordoras make frequent trips to the surface to gulp air, while other will exhibit signs of laboured breathing, such as gasping at the surface or very rapid ventilation of the gills. Cichlids often dart about frantically, while bards tend to adopt odd swimming postures.

If conditions remain poor, the fish start to lose condition rapidly, becoming subject to opportunistic infections such as whitespot, finrot, and fungus. Eventually, the fish die from ammonia or nitrite poisoning. For inexperienced aquarists unaware of the early warning signs, it is usually the sudden death pf most of their fishes that finally sounds the alarm that something isn’t quite right…

Stage one: the ammonia spike

When brand new aquarium is set up, it passes through three distinct stages. The first of these is a rise and fall in the concentration of ammonia, known as the ammonia spike. Ammonia is extremely toxic to fish, with as little as 0.5mg/L being potentially deadly to many species. Once the nitrosifying bacteria get established, the ammonia concentration declines quite rapidly, and often this particular part of the cycling process will be finished within a couple of weeks, at which point the ammonia concentration in the aquarium should be zero.

Stage two: the nitrite spike

A few days after the ammonia concentration has started to decline you should begin to notice a rapid rise in nitrite concentration. This nitrite is of course what the nitrifying bacteria need, and so this is the part of the cycling process where they begin to get established in the filter. Nitrite is marginally less toxic to fish than ammonia, with the critical danger level being around 1.0mg/L. The nitrite spike usually reaches a peak around three to four weeks after the aquarium is set up, after which point the nitrite levels quickly drops down to zero, indicating that the nitrifying bacteria have fully colonised filter.

Stage three : rising nitrate

After about six weeks ammonia and nitrite levels should be zero, and this means that the aquarium has reached the third stage in the cycle, where the filter is fully matured and the only waste product the aquarist has worry about is nitrate isn’t particularly toxic, and levels of 50 to 100mg/L are usually safe for most standard community tropicals. 

Regular water changes are usually enough to dilute the nitrite, keeping the ambient levels low enough for most fish to thrive. However, a few freshwater species are sufficiently intolerant of nitrite that the concentration will need to be kept below 20mg/L. rift valley cichlids and discus are among the best known of these nitrate-intolerant fishes, but mollies kept in freshwater rather than brackish tanks seem to be similarly sensitive.

Quick fixes

So what do you do if your aquarium is suffering from new tank syndrome and your fish are starting to look unhappy. The first thing to do is a water change. A 50% water change will make a huge difference, and performed daily this can get you through the first dangerous weeks of fish keeping without suffering any fatalities. 

The filter bacteria will not be inconvenienced by this, and the idea that they need high levels of ammonia and nitrite to get establish is erroneous. So, along with your nitrite and ammonia test kits, buy a big bottle of dechlorinator and be ready with your bucket and hosepipe to perform large-scale water changes every day.

It is also important to only use hardy fishes while cycling an aquarium. Goldfish and danios work well in freshwater tanks, and black mollies do the job nicely in brackish water tanks. Hardy barbs, such as rosy bards, also work well. Although guppies have often been recommended for cycling tanks in the past, the rather delicate fancy guppies offered for sale are not really up to this job, though wild-caught guppies (if you can find them) may well be. Particular fishes to avoid are loaches, cichlids, and oddballs such as pufferfish.

One way to jump-start a filter is to seed it with filter media taken from another aquarium. A mature filter (at least six month old) can stand to lose up to 50% of its filter media without major problems. Put the media taken from that filter into the new filter, and hey presto, the cycling process is almost entirely leapfrogged. Of course, this does rather depend on not killing the bacteria while moving them from one filter to the other. Treat the bacteria as you would fish: do not expose them to the air, and don’t subject them to large changes in water chemistry or temperature either.

Another way to jump start a filter os to use products such as Tetra SafeStart and Marineland BioSpira. These products contain cultures of bacteria said to colonise a new filter so quickly that fish can be safely introduced at once. While this sounds almost too good to be true, many aquarists have used them with great success. That said, it would still be wise to perform regular ammonia and nitrite tests for a few weeks after using them, and of course carry out water changes as required.

Fishless cycling

When setting up a tank, the temptation is to add too many fish at once, and this often leads to deaths as some of the fish fail to put up with the ambient levels of ammonia and nitrite. Even if you use just a few hardy species, those fish are still being subjected to some pretty nasty water conditions, and if you don’t want danios or goldfish, what do you do with them after you’ve finished cycling the tank? In recent years fishless cycling has become increasingly favoured as the more humane and flexible approach.

Traditionally, this was done by throwing in bits of meat or seafood and just letting nature take its course. As this stuff decayed, it produced ammonia, and that drove the colonisation of the filter by the bacteria. The more modern approach is to add daily doses of ammonia bought from a pharmacy or chemical supplier. Ammonia is of course highly toxic, and should be kept away from pets and children. The exact amount will need to be worked out by trial an error; add some to the aquarium, measure the concentration with an ammonia test kit, and then either add more ammonia or dilute with de-chlorinated water as required. Once you’ve worked out the amount you need to raise the concentration of ammonia in the aquarium to one to five-mg/L, make a note of this and add a similar dose every day. Each day or two, test with your ammonia and nitrite test kits. With luck, you should see the ammonia level peaking first and then the nitrite level, until eventually both settle down to zero indicating that the cycling process has reached completing. 

New tank syndrome is one of those things every aquarist has to deal with. Fortunately, it isn’t that difficult to manage properly, and by using fishless cycling or jump-starting the filter it can even be side-stepped entirely.

Please Support Us

Important of PH for koi fish

The importance of pH

As koi keepers we are more water keepers than biologists, and as water consists of H²O (as well as everything else dissolved within it) we owe it to our koi to understand a little chemistry. This will then increase our success and fulfilment, ultimately benefiting our koi.

Water is an amazing substance that makes life on earth possible. Besides making a pond ‘wet’ and providing something for our koi to swim in, water enables all the necessary chemical reactions to take place that help maintain a pond’s health and balance.

Water is the world’s best solvent. You can tell where water has been by analysing what it has dissolved in it. For this reason, the water in an upland, mountain stream is relatively low in dissolved minerals, whereas the opposite is true for a lowland river or lake. A koi pond is best modelled on the chemistry and water quality found in a lowland lake as this is the natural habitat of the wild-type ancestors of our koi.

Water and ions

A molecule of pure water (H²O) consists of two hydrogen atoms joined to one oxygen atom. In a pond, the water molecules separate (or dissociate) into ions – positively charged hydrogen ions (H+) and negatively charged hydroxyl ions (OHˍ). These ions are constantly forming and reforming and will do so with any ion of an equal and opposite charge. It is this characteristic of water that makes it such an excellent solvent.  For example, common salt – sodium chloride(NaCI) will dissolve readily in water forming sodium ions (Na⁺) and chloride ions (CI). This is true for many other elements and compounds, meaning that each aquatic environment in the world, will have its own unique chemistry.

pH

pH is a measure of the acidity or alkalinity of a substance and is an important measure for pond water. It is measured on a scale of 0 to 14, where 7 is neutral, below 7 is acidic and above 7 is alkaline. 

Pure water is neutral (neither acid or alkaline) and is the standard against which acidity and alkalinity is measured. pH actually measures the quantity of free hydrogen ions (the ‘H’ in pH) and recognises that free hydrogen ions make a substance acidic. More hydrogen ions relative to hydroxyl ions will make the pond acidic, more hydroxyl ions relative to hydrogen ions will make the pond more alkaline – so pH is a matter of balance. 

Taking lowland lakes as our pond’s model for water quality, our pond’s pH must be alkaline – being stable between 7.0 and 8.5.

why koi prefer slightly alkaline water?

As descendants of carp, our koi are a lowland, still water fish. By the time fresh, clean and relatively pure mountain water has reached their natural habitats, it would have picked up an array of salts and minerals, making the lowland water alkaline and hard. 

As their physiology has become adapted to this water chemistry, a complete filter system must be provided with a similar pH and water quality in ponds or they will become stressed. 

The target pH is between 7.0 and 8.5.

Processes in a pond that can affect its pH

As pond keepers, we should aim for two things when managing our pond chemistry.

·         A water quality that is within our koi’s natural limits (i.e. what their physiology is adapted to and able to tolerate)

·         Having achieved a suitable water quality, that it remains stable and within our fishes’ natural limits to avoid stress and disease.

This especially applies to pH. There is a constant tug-of-war occurring in koi pond where various natural factors conspire to alter the pH with a tendency to cause fish problems. Essentially there are 3 problems that you may need to address in your pond.

·         The pH is consistently too low.

·         The pH is consistently too high

·         The pH is very unstable and prone to wild fluctuations.

What if pH is less than 7.0 and becomes acidic?

In effect, speaking chemically, this means that there is an abundance of free H⁺ ions. A number of natural biological processes will put pressure on the pH of a koi pond to become acidic.

a.       Biological filtration. When koi release ammonia (NH³) they are releasing nitrogen and hydrogen ions. When that ammonia is broken down by bacteria into nitrite (NO²) the three free hydrogen ions are released into the water, causing a drop in pH. As ammonia excretion and biofiltration proceed unabated in every pond, there is a relentless downward pressure on pH in every pond. If the pH is allowed to drop below 7, then the addition of further free hydrogen ions accelerates the drop in pH, leading to a pH crash, causing your fish and other aquatic life real stress.

b.      Respiration. Plants (including blanketweed), fish and bacteria respire constantly taking in oxygen and releasing carbon dioxide. This process can also cause the pH to drop as the carbon dioxide combines  with water to form carbonic acid. Excessive plant growth can cause the pH to drop to extremes at night, rising again out of the danger zone in the day as plants utilise the carbon dioxide in photosynthesis.

A drop in pH in a pond to below 7 will lead to dramatic changes in koi health, particularly if they are long term. 

Colours in koi are likely to fade through the deposition of excess mucus while in extreme cases, koi may even be seen to gasp at the surface. Acidic pond water is also likely to be corrosive to exposed plastic and metal surfaces, causing the pond water to become a toxic cocktail of contaminants.

What if the pH exceeds 9.0?

From experience, an excessively high pH is less extreme on our koi than a low pH, but should still be avoided. While a drop in pH is caused quite naturally, excessively alkaline water is likely to have been caused by a pollutant, with cement or builder’s lime the No.1 suspect. 

The symptoms of an excessively alkaline pond will cause fish to secrete excess mucus and also lead to gasping at the surface, very similar in fact to those when fish experience acidic conditions.

A buffer is a chemical that when added to a pond, will help to stabilise a suitable pH. The natural tendency is for a pond’s pH to become acidic. A buffer reacts with any excess hydrogen ions (if and when an excess arises) and will release them back again into the pond water should the pH rise too high. 

The most widely used buffer in and around ponds is calcium carbonate (CaCO³). This can be in the form of crushed shells, limestone gravel or similar material.

How a buffer works in your pond

Let’s say, through extreme levels of respiration, carbon dioxide is released into the water. This combines with water, to form carbonic acid, which dissociates into two different ions.

Example: H²O + CO² H²CO³ H+ + H+ + CO³²-

The free hydrogen ions have a potential to make the water acidic.

Adding a buffer – such as calcium carbonate (CaCO³) to ‘soak up’ those free hydrogen ions, prevents the pH from dropping.

By adding limestone gravel to your filter, the following will occur.

CaCO3 + H2CO3  Ca(HC03)2  Ca++ + HC03- + HC03-

Limestone + carbonic acid equals Calcium bicarbonate, which dissociates into Calcium and bicarbonate ions (The hydrogen ions are no longer ‘free’ so do not contribute to the pond’s acidity).

This buffer will also work in reverse, releasing hydrogen ions back into the water should the water become excessively alkaline. For example, when the pH rises towards pH9, the calcium bicarbonate (which is now dissolved in the water) will release its hydrogen ions, causing the pH to drop slightly (but still remain alkaline), leading to a deposition of insoluble calcium carbonate onto submerged surfaces – including some plants.

Note

Water is an excellent solvent. Any substance that become dissolved in a solvent is called a solute. So salt (the solute) is dissolved in water (the solvent) to make a salt solution. A solution, if sampled at any number of points will be made up of precisely the same proportions of solute and solvent.

Please Support Us