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Nothing is more important when it comes to aquarium maintenance than regular partial water changes. The adage “an ounce of prevention is worth a pound of cure” certainly applies here.
One frequently reads of products that will reduce the need for water changes. Chemical media (carbon and such) may adsorb, absorb or change certain pollutants, but there is a finite limit to this and in some cases the pollutants return to the aquarium water in a different form that is still harmful. Some forms of bacteria will also release these adsorbed pollutants back into the water. And such chemical media frequently also adsorb beneficial nutrients which further worsens the state of the aquarium. Water changes also replenish essential substances such as minerals and ions. In the final analysis, there is no amount of filtration with any media that can duplicate the benefit of a regular partial water change. Everything that goes into an aquarium remains there in some form until we remove it.
The water in the fish’s natural habitat is not static but constantly changing. There are water currents in streams and rivers; thermal currents in ponds and lakes; a regular influx of fresh water from rain and snow melt. Aside from all this, the ratio of fish to water volume is infinitely greater than what we maintain in any home aquarium. The toxins the fish expel—which include ammonia through respiration, solid excrement, urine, pheromones, and allomones—are regularly being dispersed. In nature, these substances are dealt with “naturally,” but the aquarium is a closed system and the operation of nature is greatly restricted. This “crud” is partially handled by filtration but no matter how much filtration you have on your aquarium, crud in some form continues to accumulate (Boruchowitz, 2009). The regular partial water change improves this situation considerably by injecting fresh water into the system as it removes a given quantity of the toxins. This is very important to the long-term health of the fish, and live plants will benefit too. The volume and frequency do somewhat depend upon the specifics of the aquarium, but as will be evident throughout this article, there can be no doubt whatsoever that the more water that is changed and the more frequently, the healthier will be the fish. And water stability is virtually impossible otherwise.
An aquarium without regular water changes is like living in a sealed room without fresh air. Anyone who has worked in an air-sealed office building knows about this; regardless of the air conditioning system, it just is not the same as opening the window for fresh air. Like that air, the water in the aquarium becomes stale very quickly. Fish are constantly taking in water via osmosis, and they remove the minerals and expel the waste water along with any pollutants removed by their kidneys; an average-sized tetra produces 1/3 of its body weight in urine every day, so this quickly accumulates.
Many aquarists wrongly assume that a rise in nitrates (or a drop in pH) is the trigger for a water change. But this is waiting too late; the health of the fish and the aquarium’s biology has already been compromised if it shows up in these tests. The whole idea behind regular partial water changes is to prevent this from occurring, by maintaining a truly stable biological system.
1. Removing pollutants
The natural bacterial processes that break down toxins in the aquarium do not remove them completely, but change them into another form that may be less but nonetheless still toxic; an example understood by most aquarists is the nitrification cycle whereby ammonia is changed into nitrite which is then changed into nitrate. More recent scientific studies have determined that nitrate levels above 20ppm are detrimental to most fish in our aquaria, and some will be negatively impacted even at 10ppm.
And there are many others. Waste can be processed but it remains—until the water is changed.
Pheromones and allomones. These are chemical substances released by fish, plants, and algae. Biology Online defines them thus:
Pheromones: chemical substances which, when secreted by an individual into the environment, cause specific reactions in other individuals, usually of the same species. The substances relate only to multicellular organisms. This includes kairomones [these are released by flowers].
Allomones are repellent pheromones that induce a behavioural or physiologic change in a member of another species that is of benefit to the producer.
Just as hormones affect the body they are in, so pheromones and allomones released into the environment affect the bodies of other fish. These vary in function: some are used as communication between fish of the same species in a shoal—sometimes as a warning of danger; some initiate spawning behaviour between mates; some limit and even prevent growth of both the fish that releases them and other fish in the tank; some are warnings of aggression to other fish; and some indicate the fish is under stress.
Reduction in microbial populations and their metabolites. Microbial population refers to all those microorganisms living in the aquarium water; included are pathogens—microorganisms such as a virus, bacterium, prion, or fungus, that causes disease. Maintaining fresher, more stable water by removing all these pollutants is one of the easiest ways to keep the fish healthy. Regular water changes can also help to keep algae from increasing.
2. Water Stability
This encompasses a number of factors. GH (general mineral hardness) and electrolytes must be replenished, and this requires either a water change or additives. Fish physiology will only function at its best under stable and appropriate levels, and these are important for the fish’s osmoregulation. Maintaining proper and stable pH and KH (carbonate hardness or Alkalinity) is also tied to regular water changes.
DOC (dissolved organic carbon) accumulates, and while this can be assimilated by plants, it is easy for DOC to overwhelm the aquarium, particularly one without plants, and this has serious consequences for the fish.
Nitrogenous substances in the water column such as ammonia and nitrite can be removed before they enter the nitrification cycle and thus help to keep nitrates lower. This is again more important in tanks without live plants. A rise in nitrates indicates a biological imbalance.
Total dissolved solids (TDS) refers to the content of all organic and inorganic substances that are present in the water in a molecular, ionized or micro-granular suspended state. These build up from many sources: water conditioners and any substance affecting water chemistry; fish foods; organic matter; ions, minerals, salts and metals. As TDS increase, the ability of the water to hold oxygen decreases proportionally. The level of TDS also affects fish directly [see my article on stress for more detail]. TDS can only be removed by water changes.
Replacing trace elements and minerals. These are important to the health of the fish, as well as the stability of the water chemistry. Over time they are used up or filtered out. If they aren't replaced, the pH of the water will drop. Furthermore, the lack of trace minerals will adversely affect the vigor and health of the fish and plants. Giving your fish fresh water regularly is akin to taking vitamins to remain strong and healthy.
[continued in next post]
One frequently reads of products that will reduce the need for water changes. Chemical media (carbon and such) may adsorb, absorb or change certain pollutants, but there is a finite limit to this and in some cases the pollutants return to the aquarium water in a different form that is still harmful. Some forms of bacteria will also release these adsorbed pollutants back into the water. And such chemical media frequently also adsorb beneficial nutrients which further worsens the state of the aquarium. Water changes also replenish essential substances such as minerals and ions. In the final analysis, there is no amount of filtration with any media that can duplicate the benefit of a regular partial water change. Everything that goes into an aquarium remains there in some form until we remove it.
The water in the fish’s natural habitat is not static but constantly changing. There are water currents in streams and rivers; thermal currents in ponds and lakes; a regular influx of fresh water from rain and snow melt. Aside from all this, the ratio of fish to water volume is infinitely greater than what we maintain in any home aquarium. The toxins the fish expel—which include ammonia through respiration, solid excrement, urine, pheromones, and allomones—are regularly being dispersed. In nature, these substances are dealt with “naturally,” but the aquarium is a closed system and the operation of nature is greatly restricted. This “crud” is partially handled by filtration but no matter how much filtration you have on your aquarium, crud in some form continues to accumulate (Boruchowitz, 2009). The regular partial water change improves this situation considerably by injecting fresh water into the system as it removes a given quantity of the toxins. This is very important to the long-term health of the fish, and live plants will benefit too. The volume and frequency do somewhat depend upon the specifics of the aquarium, but as will be evident throughout this article, there can be no doubt whatsoever that the more water that is changed and the more frequently, the healthier will be the fish. And water stability is virtually impossible otherwise.
An aquarium without regular water changes is like living in a sealed room without fresh air. Anyone who has worked in an air-sealed office building knows about this; regardless of the air conditioning system, it just is not the same as opening the window for fresh air. Like that air, the water in the aquarium becomes stale very quickly. Fish are constantly taking in water via osmosis, and they remove the minerals and expel the waste water along with any pollutants removed by their kidneys; an average-sized tetra produces 1/3 of its body weight in urine every day, so this quickly accumulates.
Many aquarists wrongly assume that a rise in nitrates (or a drop in pH) is the trigger for a water change. But this is waiting too late; the health of the fish and the aquarium’s biology has already been compromised if it shows up in these tests. The whole idea behind regular partial water changes is to prevent this from occurring, by maintaining a truly stable biological system.
1. Removing pollutants
The natural bacterial processes that break down toxins in the aquarium do not remove them completely, but change them into another form that may be less but nonetheless still toxic; an example understood by most aquarists is the nitrification cycle whereby ammonia is changed into nitrite which is then changed into nitrate. More recent scientific studies have determined that nitrate levels above 20ppm are detrimental to most fish in our aquaria, and some will be negatively impacted even at 10ppm.
And there are many others. Waste can be processed but it remains—until the water is changed.
Pheromones and allomones. These are chemical substances released by fish, plants, and algae. Biology Online defines them thus:
Pheromones: chemical substances which, when secreted by an individual into the environment, cause specific reactions in other individuals, usually of the same species. The substances relate only to multicellular organisms. This includes kairomones [these are released by flowers].
Allomones are repellent pheromones that induce a behavioural or physiologic change in a member of another species that is of benefit to the producer.
Just as hormones affect the body they are in, so pheromones and allomones released into the environment affect the bodies of other fish. These vary in function: some are used as communication between fish of the same species in a shoal—sometimes as a warning of danger; some initiate spawning behaviour between mates; some limit and even prevent growth of both the fish that releases them and other fish in the tank; some are warnings of aggression to other fish; and some indicate the fish is under stress.
Reduction in microbial populations and their metabolites. Microbial population refers to all those microorganisms living in the aquarium water; included are pathogens—microorganisms such as a virus, bacterium, prion, or fungus, that causes disease. Maintaining fresher, more stable water by removing all these pollutants is one of the easiest ways to keep the fish healthy. Regular water changes can also help to keep algae from increasing.
2. Water Stability
This encompasses a number of factors. GH (general mineral hardness) and electrolytes must be replenished, and this requires either a water change or additives. Fish physiology will only function at its best under stable and appropriate levels, and these are important for the fish’s osmoregulation. Maintaining proper and stable pH and KH (carbonate hardness or Alkalinity) is also tied to regular water changes.
DOC (dissolved organic carbon) accumulates, and while this can be assimilated by plants, it is easy for DOC to overwhelm the aquarium, particularly one without plants, and this has serious consequences for the fish.
Nitrogenous substances in the water column such as ammonia and nitrite can be removed before they enter the nitrification cycle and thus help to keep nitrates lower. This is again more important in tanks without live plants. A rise in nitrates indicates a biological imbalance.
Total dissolved solids (TDS) refers to the content of all organic and inorganic substances that are present in the water in a molecular, ionized or micro-granular suspended state. These build up from many sources: water conditioners and any substance affecting water chemistry; fish foods; organic matter; ions, minerals, salts and metals. As TDS increase, the ability of the water to hold oxygen decreases proportionally. The level of TDS also affects fish directly [see my article on stress for more detail]. TDS can only be removed by water changes.
Replacing trace elements and minerals. These are important to the health of the fish, as well as the stability of the water chemistry. Over time they are used up or filtered out. If they aren't replaced, the pH of the water will drop. Furthermore, the lack of trace minerals will adversely affect the vigor and health of the fish and plants. Giving your fish fresh water regularly is akin to taking vitamins to remain strong and healthy.
[continued in next post]
