What is filtering for?
Like any living organism, fish, as a result of their vital activity, emit various substances that pollute the water, making it poorly suitable for fish. We also use filtering for ourselves, starting from a separate bathroom in the apartment and ending with weekly cleaning of the room – we vacuum and sweep the floor (unfortunately, I saw many aquarists who had filtration in the aquarium at an unattainable height, and the filtering in the room left much to be desired ). Fish are forced to live in the literal sense of the word surrounded by their own garbage. In addition, it leads to stress in them and, as a result, growth retardation, loss of color and poor resistance to disease. I wonder how you would feel, living all your life in a pile of garbage? The problem is aggravated by the fact that in the aquarium there is usually a lot of fish and little water, while in nature it is the other way around. Obviously, a small aquarium with large fish requires more attention than a large planted aquarium with several small fish, in which, in principle, filtration can be supported by microorganisms and plants in it. An important source of garbage in an aquarium is food, which is usually much more than enough.
Unfortunately, clean-looking water is not a sufficient condition for the successful keeping of fish. Very often, the fish begin to die in the water, which is crystal clear and the novice aquarist wonders what happened in the aquarium that was bought a week ago and 10 beautiful fish were planted in it, which suddenly died. The answer is simple – the presence of ammonia in the water, which is not processed by bacteria that are not in the new aquarium, leads to the death of fish.
Ammonia and ammonium are formed during the decomposition of the protein molecule and are the most toxic of the waste products of fish that release it during breathing. They are also formed as a product of decay of organic matter in water.
Ammonia (ammonia) is dissolved in water with the formation of a pair of ions – ammonium (ammonium) NHfour and OH.
However, at elevated pH of the water (i.e. more alkaline water) and temperature, free ammonia NH is formed.3 and the molecule is water. Free ammonia is much more toxic to fish than its ion. For example, at pH8, only 5% of ammonia exists in its free form, while time at pH9 is already 20% of free ammonia. Therefore, an aquarium with African cichlids requires much more attention to the purity of the water (but this does not mean that you can ignore the filtering in an aquarium with South American fish living in acidic water, the effectiveness of bacteria that process ammonia lower in acidic water). An aquarium with a higher temperature also requires more attention, for example, when the temperature rises from 15 ° C to 25 ° C, the content of free NH increases.3 almost doubled. The toxicity of ammonia is reduced in salt water, by about 30: than in fresh water with the same parameters.
In the future, the word ammonia will be understood as two chemical compounds – ammonia (NH3) and ammonium (positively charged ion NHfour + ). Since both of them are present in the water, both are poisonous, then, from the point of view of an aquarist, there is no difference between the description of filtration processes.
The lethal level of ammonia is about 0.2 – 0.5 mg / l for various fish, the maximum allowable level is 0.01-0.02 mg / l. However, at this level, some fish are exposed to stress, which weakens their resistance to disease. Therefore, we can say that the level of ammonia in the aquarium should be zero (when testing water, the indicator color is less than the first scale division)
As a result of biological filtration, ammonia is converted to less toxic nitrites (with the letter I) and then to much less toxic nitrates (with the letter A). The level of toxicity of nitrates for delicate fish is 50-300 mg / l (for caviar and fry, they are much more toxic). More on this is written in the section on biological filtration.
Do not think that the ammonium ion is not dangerous. It is dangerous too, but to a lesser extent. Lowering the pH and temperature of the water leads to a decrease in the toxicity of ammonia, but at the same time, the effectiveness of bacteria processing ammonia decreases. The optimal conditions for them are neutral water (pH about 7) and temperature about 30C. At pH below 5, their vital activity practically stops. Therefore, do not pour acetic acid into the aquarium to reduce the toxicity of ammonia. It will decrease, but no one will recycle.
Types of filtering
By its mechanism, filtering can be divided into three large groups:
- Mechanical – the filter is used to delay large, not dissolved in water, debris. Since fish excrement and food residues are a source of toxic ammonia, the best way to prevent rotting is to remove them from the aquarium (besides, large garbage in the aquarium looks ugly). This is achieved by using a coarse filter or sponge, which must be rinsed regularly. Such mechanical filtration can also include regular cleaning of the bottom with a siphon, which should be done at every water change. Mechanical filtration can also be used to purify water from suspended particles, for example, using a diatomaceous filter that can even filter out algae causing "green water."
- Chemical – filter removes dissolved substances. The most popular type of chemical filtration is the use of activated carbon. Another way is to use different ion exchange resins (for example, zeolite (zeolit) to remove ammonia from water). Chemical filtration can also include flotation columns (protein skimmer), which remove organic molecules from water before they are decomposed with the release of ammonia. Ozonizers, to some extent, also perform chemical filtration by oxidizing organic matter.
- Biological – the most important type of filtration, which results in the conversion of toxic ammonia into non-toxic nitrates. This is done by bacteria. Details of this filtering are discussed below. Absorption of ammonia, nitrates, phosphates and other substances by plants and algae can be attributed to this type of filtration. This is described in more detail in the section on algae.
There is no clear boundary between these types of filtration. for example, a mechanical filter or activated carbon also serves as a site for the colonization of bacteria that decompose ammonia. Bio-filtering environment delays litter, etc. Therefore, we must talk about the totality of all types of filtering.
Nitrate cycle in an aquarium
This cycle is one of many biological cycles occurring in an aquarium. But it is he who is most important for understanding the process of filtering water from toxic ammonia.
Here the cycle is depicted in a simplified form and only the main details are shown. Ammonia and ammonium are formed during the respiration of fish, decay of plants and other organic matter. About their toxicity mentioned above. As a result of the activity of bacteria, ammonium is converted into non-toxic nitrates, which are absorbed by plants. Along with nitrates, plants absorb ammonia / ammonium and nitrites, even preferring ammonia / ammonium, because they use less energy, but rely on this process only in exceptional cases, when the aquarium is an overgrown garden, so for beginners aquarists such filtering method too complicated.
In the places of the aquarium where there is not enough oxygen, the reverse process takes place – anaerobic bacteria extract the oxygen they need from the nitrate molecule. This process is used for biological denitration – reducing the content of nitrates in water. In an aquarium, such processes develop, for example, in the ground, where there may be a lack of oxygen. It should be noted that bacteria also extract oxygen from sulphates and this produces H2S gas that has the smell of rotten eggs. It is this gas that bubbles up from the rotten soil, if it is stirred. This gas is very toxic for fish and when it appears it is necessary to do the ground thoroughly.
Magic word – bio-filtering
Probably, many have seen this word in the advertising of a filter / filler to the filter, etc. Even used such a word – biofilter. So what does it all mean? And whether you need a special branded ceramic filler in the filter for a lot of money in order to have bio-filtration in the aquarium.
The process of bio-filtration is the conversion of ammonia, which is toxic to fish, into non-toxic nitrates (with the letter "a"). This process is carried out by bacteria (hence the word bio, in contrast to the chemical filtration of ammonia). Simple enough. From this it is clear that for effective bio-filtration you need bacteria, a place for them to settle, oxygen (since bacteria need oxygen). Bacteria will start themselves in an aquarium, about a place to move in and oxygen you have to take care. For their vital activity, bacteria need a place to settle. They cannot process organic matter by swimming in water. Why? Put yourself in the place of the bacteria. You have no arms or legs, so you can grab only that piece of food that got into your mouth, there is no possibility to pick it up at a distance – you can only proceed with saliva. You swim at the same speed as food – there are no arms or legs. Clear? In general, it is best when you are sitting motionless, and the food gets into your mouth. In principle, bacteria lodge everywhere – they are on the walls of the aquarium, soil, plants, etc. But the surface area of the walls of the aquarium is small, so you need to give them more free living space. It all depends on your imagination. If you are using a bottom filter, then the place of bacteria is the soil and the board under it. For the internal filter, this place is a sponge, whose surface, due to its porosity, is very large. For a canister filter – fillers – a sponge, ceramics, pieces of Pepsi-Cola tubules (or Coca-Cola, who loves it more), etc. Porous ceramics have a very large surface area relative to volume. Also, in small pores, where there is a lack of oxygen (all oxygen is consumed by bacteria that settle at the entrance to the holes), anaerobic bacteria settle, which decompose nitrates – the denitration process. This is similar to the denitration process that occurs in a reef aquarium using live rock. Denitration is considered separately and is not so important for maintaining the aquarium in good condition.
The important point is the presence of oxygen in the water. The process of bio-filtration is an oxidative process and requires oxygen. To do this, use all sorts of tricks – "bio-wheel" (bio-wheel), splashing water over the filter medium (trickle, wet-dry filters), etc. All this is discussed in the relevant sections. With a lack of oxygen, the bio-filtration process stops, bacteria can die, the reverse process begins with the formation of ammonia, etc. For example, you can not leave the external filter without the flow of water for the whole day. If you need to turn off the filter during the treatment of fish, it is best to place it in a separate container and turn on the nebulizer to saturate the water with oxygen. For the same reason, you should regularly clean the filter, preventing it from becoming overgrown with dirt. Only those bacteria are effective that are in contact with water and have access to oxygen. The bottom layers of bacteria are useless. In this sense, sand (fluidized bed) filter, in which there is a constant mixing of sand.
The process of absorption of ammonia and other organic compounds by plants and algae can also be attributed to bio-filtration. Interestingly, plants prefer ammonia to nitrates. On this principle, filters are built, in which the main element are plants or algae – algae-scrubber.
As a result, the process of bio-filtering is not something complicated and an understanding of its basic principles makes it possible to think out ways to increase its effectiveness.
Launch a new aquarium
To avoid this, you need to try to understand what is happening in the aquarium when fresh water is poured into it. If you have already read this far, you know about the ammonia / ammonium toxicity, the nitrate cycle and bio-filtration. You know that you need to run bio-filtering so that fish can live in the aquarium. Of course, this is only one of the conditions. It is possible to do without bio-filtration, for example, to use chemical filtration, absorbing activated carbon with organic matter and special compounds, for example, zeolite, ammonia. Or change the water every day, But if you have a special person to change the water all the time, replace coal, etc., then you obviously don’t need to read all this, it’s better to hire a knowledgeable person. Therefore, let’s dwell on the need for bio-filtering.
In the clean water from the tap, which you poured into the aquarium, there are millions of bacteria, including those that are needed for bio-filtration. They are also carried through the air, along with the fish, on your hands, etc. Unfortunately, they are in the form of a dispute and are not suitable for bio-filtering. If you are a more experienced aquarist, then you know that it is useful to put in a new aquarium a filler from a filter from another aquarium. In this case, we must try not to bring infection. Brought bacteria on the filler can shorten the start time of the aquarium.
So what happens. You planted a few fish (unpretentious, like danios or mollies, discus is not suitable as a starter), which began to produce ammonia. Or you could pour ammonia into the aquarium – a more complicated, but less stressful way for fish (which are not there at this time) – pouring it in such a way as to maintain a concentration of 3-5 mg / l. After a few days, the ammonia concentration jumped to a noticeable level. If you have brought live bacteria, then they slowly set to work, if not, then the bacteria that are in hibernation smelled the smell of food. But they are not in a hurry to wake up – it makes sense to wake up if you are sure that the smell of food comes from the kitchen, not from the neighbor’s window, and it smells delicious, which means fast food. Otherwise, only frustration – woke up, but there is no food in the kitchen or everyone is already eating up. So talk about bacteria. When they are “confident” that the concentration of ammonia is sufficient and lasts for a while, they will “hatch” and get down to business. Initially, these will be bacteria from the genus Nitrosomonas (the name is generally optional). They convert ammonia to nitrite. At the same time and begin to grow and other bacteria that eat organic. Countless species replace each other. A sort of miniature evolution -Jurassic park. As a result, the water becomes cloudy. Do not be nervous and run to buy water clarifiers – it will acquire transparency itself, in a few days. Do not rush to change the water. Of course, if the turbidity is due to the fact that the soil is poorly washed, then something needs to be done. In this initial period of growth of ammonia concentration (it may last a week or a half or less if there is already a culture of bacteria), watch its level, changing the water only if the level begins to become dangerous for fish. For this endurance fish are used. Then, the level of ammonia begins to fall, and very quickly, within a couple of days. This means that the bacteria started their activities and converted all the excess into nitrites, which are also poisonous for fish. Those. The first phase of bio-filtering is working. From this point on, the ammonia level should be zero.
If you measure nitrites, you will notice that their level is growing very rapidly, since all the ammonia is processed into nitrites. At the same time, Nitrobacter bacteria, which are responsible for the second phase of bio-filtration, the conversion of nitrites to non-toxic nitrates, are beginning to wake up slowly. After a week and a half, the nitrite level will drop to zero and the nitrate level will slowly rise. This means that the biofilter is working. In general, this period can last two to three to four weeks, depending on the initial conditions, temperature (bacteria prefer a temperature of about 30 degrees), acidity (bacteria like neutral water with a pH of about 7)
Now you can begin to change the water on a regular basis and plant new fish. Do it slowly. The bio-filter has stabilized at such a level that it can process a certain amount of ammonia. Each new fish means an additional amount of ammonia and the bio-filter needs to adapt to new conditions, which takes time.
There is nothing difficult in launching an aquarium. It is important to understand the processes occurring in it and patience. Schematically, the process is depicted in the graph.
The best type of filtration is water change.
Probably all of you have heard stories about aquarists who do not change the water for years, but only add fresh ones to replace evaporated ones. And all the fish live in such aquariums perfectly, sometimes there are only problems with some fish, for example with apistograms. Well, they do not live and all. And why – it is not clear. It’s not meant to be. And since the water is beautiful – clean and does not smell. Such an opinion was common in old books. Even aquarists were changing with old water from aquariums. Many fish can live well in a similar aquarium. And other fish can not live – they give fresh water.
If you are an inveterate supporter of non-replaceable water, then I can not convince you. For others, I can suggest an experiment – start changing the water for a few days to fresh, 15-20% by volume of water and compare the behavior and color of the fish. Abundant change of water at a slightly lower temperature stimulates spawning in many fish. Why? As always, put yourself in the place of fish – the season of drought. the water dries up, from the river, where you frolicked so much, there were small pools, the concentration of salts, nitrates, etc. increased to such an extent that the scales stand on end. temperature is close to soup. And here comes a heavy cold rain, a few days, a week. What does it mean? The rainy season has begun – everything comes to life, there will be plenty of food for your fry, plenty of water – clean water (children need to walk in the fresh air), plenty of shelters. What should be done? That’s right, that’s it.
As a result of the nitrate cycle, nitrates accumulate in water, which, although not poisonous in reasonable concentrations, does not adorn life. The water accumulates phosphates from feed, which promote the growth of algae. It is also full of any other rubbish (as much as your wife told you – do not smoke in the room), including those unknown to modern science. In short, all this can be expressed as:
Change over time
Optimal spacing for most fish
Activated carbon for and against
Activated carbon is one of the most common filler for filters and is used for chemical filtration (like any filler, it is also a medium for colonization of bacteria performing bio-filtering, but the efficiency of coal as a chemical filter decreases, because that the pores are clogged). Activated carbon has a large number of microscopic pores and, due to this, absorbs (absorbs and adsorbs) organic molecules from water. It is especially effective for filtering organic matter, which gives the water a yellowish color, odor, etc. It is also effective for the removal of heavy metals from water, chlorine from water during osmotic filtration. Activated carbon does not remove ammonia / ammonium, nitrates and phosphates from water — other fillers (for example, zeolite) are needed for this. The ability to remove certain substances depends on the type of coal, pore size, etc.
Activated carbon is made from ordinary coal, wood and other materials, including exotic materials like bamboo and coconut peel. Initially, it is heated to a high temperature in the absence of air, then activated at an even higher temperature, up to 1000 ° C and higher in the presence of steam, air, etc. The result is an extremely porous material. In the manufacturing process, it can be washed in various substances, acids, etc.
The effectiveness of activated carbon in an aquarium depends on many factors:
- Type of coal used – Try to use a good coal, designed for aquarium. The coal used for gas cleaning is prepared in a different way than the coal used for water purification and has other characteristics. Try to avoid using coal from drinking filters. The coal used for drinking filters is washed in phosphate acids. It has a low pH value (to suppress the growth of bacteria in it – you hardly need a colony of bacteria in the drinking filter), so it will “acidify” the water and release phosphates that promote algae growth.
- Type of substances removed and water flow rates – molecules of different sizes are removed with different efficiencies (smaller molecules are faster). The rate of water purification depends on the concentration of the substance to be removed – with a large concentration, removal occurs faster, but less time is required to remove a smaller amount. The slower the flow of water through the coal, the longer the contact time and the more efficient the removal. On the other hand, in a closed system, water passes repeatedly through the filter.
- Coal Sizes and Porosity – efficiency depends on the ratio of pore volume to coal volume. The larger the pores, the more efficient the coal.
- Time spent coal in the filter – as it is used, the efficiency of coal decreases due to clogged pores. On the other hand, bacterial and organic films that grow on carbon also reduce filtration efficiency. Therefore, coal (as well as other filter media) must be regularly washed and changed. Try to use a mechanical filter in front of the coal to filter out large particles. Do not leave long coal in the aquarium. especially when filtering poisonous substances, antibiotics used to treat fish. Although this happens rarely, coal may begin to release previously absorbed substances into the water.
How to choose a good activated carbon? It is best to buy special coal intended for aquariums. Try to pay attention to the following characteristics:
- Particles should be small – about 1-2 mm in size (although some firms make and larger)
- The particles should be solid and not shiny in appearance. If the particles are soft and shiny, then this is most likely normal, not activated, coal.
- Coal must be light – it means that there are many pores in it. The particles should repel water and the pores are filled with air – at the first moment the coal floats and if you listen, you can hear the air coming out of the pores – if the coal is heavy and sinks, then it is not of very good quality.
- Coal should not contain large amounts of dust. It will always be, so before using the coal should be washed in running water.
How much coal should I put? It depends on the purpose for which you use it. For example, in order for the water to be crystal clear, it can be used in large quantities and changed more often (for a reef aquarium, A. Thiel recommends using 250 g per 50 liters of water and changing it once a month – which is obviously a lot for a regular freshwater aquarium). On the other hand, it can be used in moderate quantities (about 5-20 grams per 50 liters) and can be changed when the water gets a yellowish tint. it is necessary to take other measures) within 2-4 months. More accurate recommendations cannot be given – it all depends on the specific conditions. If you have unlimited reserves of coal – you can change it often, if the water has acquired a yellowish tint (and it bothers you), then it is time to change the coal. If you filtered the antibiotic after treating a disease in an aquarium, then you need to change the coal. To determine that the water has acquired a yellowish tint, use a strip of white plastic (for example, cut from a plastic can), part of which is painted in yellow-brown color (for example, a felt-tip pen for applying indelible inscriptions, etc.). If, when immersed in water, the border between white and yellow is not visible, then it is time to change the coal.
A few words about the recovery of coal. It can not be fully restored at home. Although, if you have a furnace for heating to a temperature of 1000 ° C without access to air, then you can try. If coal was not used for very long, it can be rinsed under the tap and / or heated in an oven – this will remove some amount of organic matter and open some of the pores. The effectiveness of this recovery is doubtful, and for old coal it does not make sense – it is better to take a new one.
Now a few words why you should not abuse coal in the aquarium. Usually beginners use it in the filter, believing that this is a panacea for all problems.
- Coal does not remove the most toxic substance in aquarium water – ammonia. Of course, when bacteria settle on it, they will recycle ammonia in the process of bio-filtration. But the use for such purposes is expensive.
- Coal does not remove nitrates and phosphates, which are one of the main problems of the appearance of algae in the aquarium. On the contrary, low-quality coal will release phosphates. On the other hand, coal will absorb fertilizers necessary for plants, for example, iron bound to EDTA (used to prevent the rapid oxidation of iron)
- By making the water crystal clear, coal will mask the need to change the water – the aquarist will believe that the water should not be changed, while nitrates are going through the roof. With a regular change of water in the aquarium there should not be a lot of organic matter, and if there is a lot of it, then it is necessary to look for the cause – overfeeding the fish in the aquarium, etc. The yellowness of the water – in general, it does not really interfere within reasonable limits, on the contrary, the "South American" aquarium, has a more natural look with slightly yellowish water. Pisces does not bother at all. It is completely unwise to put peat into the filter to soften hard water, which gives off organic matter, giving the water a yellowish color and with it coal that will absorb this organic matter.
- Coal costs money that can be spent on more useful things.
As a result, we can recommend periodic use of coal – for example, prior to the introduction of antibiotics and other medical preparations into the aquarium. This removes organic matter, which reduces the effectiveness of drugs. At the same time it is good to change the water in the amount of a third to a quarter of the aquarium. Similarly, coal can be used to remove drugs after treatment. When using coal occasionally, make sure that no anaerobic conditions are formed in the pores.
In the filter, activated carbon and other fillers, including ceramics, are well kept in separate bags – then it will be more convenient to pull out and rinse them. Good bags can be made of nylon stockings – ask your friends and wives to share with you.