Total Solids basically refers to organic and inorganic matter that is either suspended or dissolved in the aquarium water.
Total Suspended Solids (TSS) refers to the amount of solid waste, decaying fish and plant matter, etc. that can be captured and held by a filter.
Total Dissolved Solids (TDS) is a measure of the combined content of all organic and inorganic substances contained in the water in molecular, ionized or micro-granular (colloidal sol) suspended form. Generally the operational definition is that the solids must be small enough to survive filtration through a sieve the size of two micrometer.
Fresh water by definition contains no more than 1500 mg/l of TDS. Brackish water contains 1500-5000 mg/l, and marine (salt) water has more than 5000 mg/l of TDS. Note that mg/l is basically equal to parts per million (ppm), and also that this is not suggesting a level of 1500 ppm in an aquarium; these are just the approximate figures for the three categories.
TDS is connected to GH (general hardness) because like GH, TDS includes the calcium, magnesium and other “hard” mineral ions; these ions are what we measure with our GH test kits. But water hardness correctly considered is more than this; both GH and KH can affect hardness and TDS levels; however, the reverse is not necessarily true. Aquarium water can have a high TDS level but a low GH and KH (Jensen, 2009). The TDS for instance also includes sodium (salt) ions, chemical substances, etc. which are not reflected in the GH.
TDS is basically everything dissolved in the water: chlorine, chloramine, ammonia, phosphate, salt, hard minerals (GH), bicarbonates (KH), etc. And almost every substance added to the water will increase TDS: water conditioner, fish foods, plant fertilizers, calcareous substances, medications, water adjustment products, etc.
The Effect of TSS and TDS in the Aquarium and on Fish
As the above definition indicates, filtration via aquarium filters will (or should) remove the TSS but will not remove any TDS from the water [see later on carbon]. While live plants can use some of them, only a partial water change effectively removes the TDS that naturally increase within the aquarium.
High concentrations of TDS may reduce water clarity, contribute to a decrease in photosynthesis, combine with toxic compounds and heavy metals, and lead to an increase in water temperature (Jensen, 2009).
But the greatest impact, and the one that is not usually apparent to the aquarist until things are too far gone, is the impact on fish. Hard water fish--as we term those species such as livebearers, rift lake cichlids, and some of the atherinids, cyprinids and catfish—can withstand higher TDS than soft water fish. The TDS in Lake Tanganyika is around 400 ppm. Compare this to the near-zero TDS in many Amazonian streams.
Fish live in water, and their bodies contain water; the fish’s cells separate these two waters, but the cells are semi-permeable, which means the cell will permit the movement of water and certain non-polar molecules to pass through either way (called osmosis) but will prevent the passage of larger or charged molecules. The way the water moves is determined by the difference in concentrations between the two waters: water of higher concentration (more dense) will attempt to pass through to the water of lower concentration (less dense) until the two are equal. If the fish could not somehow control this natural flow, it would either rapidly dehydrate or explode. But fish are able to control this through osmoregulation, a complex series of chemical processes. The water moving in or out of the fish’s body will likely have a different pH, so another set of processes controls the function of regulating the pH of the fish’s blood (Muha, 2005). Both of these processes also affect the ability of the blood to carry oxygen, and this impacts many other functions including digestion, the immune system, and so on.
The kidneys primarily work to eliminate excess water, but another function is the conservation and reabsorption of essential salts. Both processes work to maintain a specific salt/water balance. This osmoregulation of bodily fluids requires a great amount of metabolic energy. So a high osmotic pressure (caused by elevated levels of TDS outside the fish’s natural range) will overwhelm the fish with excess water and overwork the kidneys, while a low osmotic pressure (caused by TDS levels below those of the fish’s natural range) will deprive the fish of the water needed for the kidney functions (Evans, 2004).
The TDS also affects how fast water moves into the fish via osmosis. “Pure” water would pass through the fish's cells very quickly, while water with some TDS would move more slowly. Fish use their kidneys to pump this water out. The kidneys of fish that occur in hard water don't have to work very hard. Soft water fish are built by their natural evolution to live in water that they rapidly take in to flush out toxins. A small tetra will urinate more than three times its body weight every day. But the higher the TDS, the harder it is for the fish to do this, so the toxins remain longer in their bodies affecting their physiology, causing stress, and this will inevitably lead to a shorter lifespan depending upon species and levels. This may not be evident to us until the fish just dies, for no “apparent” reason. Such fish actually become dehydrated, and most suffer kidney problems. [Geisler (1987) covers the kidney deterioration in cardinal tetra due to hard water calcium with scientific data on the fish’s lifespan directly determined by the TDS of the water.]
TDS also directly and significantly impact on osmoregulation occurring in the gills. When the TDS cause a change in the osmotic pressure, the red blood cells can change shape; a low osmotic pressure will deplete the red blood cells of water, causing them to collapse, and a high osmotic pressure will inundate them with water, causing the cells to expand. Both results will seriously impact respiration.
[Continued in Part Two, next post]
Total Suspended Solids (TSS) refers to the amount of solid waste, decaying fish and plant matter, etc. that can be captured and held by a filter.
Total Dissolved Solids (TDS) is a measure of the combined content of all organic and inorganic substances contained in the water in molecular, ionized or micro-granular (colloidal sol) suspended form. Generally the operational definition is that the solids must be small enough to survive filtration through a sieve the size of two micrometer.
Fresh water by definition contains no more than 1500 mg/l of TDS. Brackish water contains 1500-5000 mg/l, and marine (salt) water has more than 5000 mg/l of TDS. Note that mg/l is basically equal to parts per million (ppm), and also that this is not suggesting a level of 1500 ppm in an aquarium; these are just the approximate figures for the three categories.
TDS is connected to GH (general hardness) because like GH, TDS includes the calcium, magnesium and other “hard” mineral ions; these ions are what we measure with our GH test kits. But water hardness correctly considered is more than this; both GH and KH can affect hardness and TDS levels; however, the reverse is not necessarily true. Aquarium water can have a high TDS level but a low GH and KH (Jensen, 2009). The TDS for instance also includes sodium (salt) ions, chemical substances, etc. which are not reflected in the GH.
TDS is basically everything dissolved in the water: chlorine, chloramine, ammonia, phosphate, salt, hard minerals (GH), bicarbonates (KH), etc. And almost every substance added to the water will increase TDS: water conditioner, fish foods, plant fertilizers, calcareous substances, medications, water adjustment products, etc.
The Effect of TSS and TDS in the Aquarium and on Fish
As the above definition indicates, filtration via aquarium filters will (or should) remove the TSS but will not remove any TDS from the water [see later on carbon]. While live plants can use some of them, only a partial water change effectively removes the TDS that naturally increase within the aquarium.
High concentrations of TDS may reduce water clarity, contribute to a decrease in photosynthesis, combine with toxic compounds and heavy metals, and lead to an increase in water temperature (Jensen, 2009).
But the greatest impact, and the one that is not usually apparent to the aquarist until things are too far gone, is the impact on fish. Hard water fish--as we term those species such as livebearers, rift lake cichlids, and some of the atherinids, cyprinids and catfish—can withstand higher TDS than soft water fish. The TDS in Lake Tanganyika is around 400 ppm. Compare this to the near-zero TDS in many Amazonian streams.
Fish live in water, and their bodies contain water; the fish’s cells separate these two waters, but the cells are semi-permeable, which means the cell will permit the movement of water and certain non-polar molecules to pass through either way (called osmosis) but will prevent the passage of larger or charged molecules. The way the water moves is determined by the difference in concentrations between the two waters: water of higher concentration (more dense) will attempt to pass through to the water of lower concentration (less dense) until the two are equal. If the fish could not somehow control this natural flow, it would either rapidly dehydrate or explode. But fish are able to control this through osmoregulation, a complex series of chemical processes. The water moving in or out of the fish’s body will likely have a different pH, so another set of processes controls the function of regulating the pH of the fish’s blood (Muha, 2005). Both of these processes also affect the ability of the blood to carry oxygen, and this impacts many other functions including digestion, the immune system, and so on.
The kidneys primarily work to eliminate excess water, but another function is the conservation and reabsorption of essential salts. Both processes work to maintain a specific salt/water balance. This osmoregulation of bodily fluids requires a great amount of metabolic energy. So a high osmotic pressure (caused by elevated levels of TDS outside the fish’s natural range) will overwhelm the fish with excess water and overwork the kidneys, while a low osmotic pressure (caused by TDS levels below those of the fish’s natural range) will deprive the fish of the water needed for the kidney functions (Evans, 2004).
The TDS also affects how fast water moves into the fish via osmosis. “Pure” water would pass through the fish's cells very quickly, while water with some TDS would move more slowly. Fish use their kidneys to pump this water out. The kidneys of fish that occur in hard water don't have to work very hard. Soft water fish are built by their natural evolution to live in water that they rapidly take in to flush out toxins. A small tetra will urinate more than three times its body weight every day. But the higher the TDS, the harder it is for the fish to do this, so the toxins remain longer in their bodies affecting their physiology, causing stress, and this will inevitably lead to a shorter lifespan depending upon species and levels. This may not be evident to us until the fish just dies, for no “apparent” reason. Such fish actually become dehydrated, and most suffer kidney problems. [Geisler (1987) covers the kidney deterioration in cardinal tetra due to hard water calcium with scientific data on the fish’s lifespan directly determined by the TDS of the water.]
TDS also directly and significantly impact on osmoregulation occurring in the gills. When the TDS cause a change in the osmotic pressure, the red blood cells can change shape; a low osmotic pressure will deplete the red blood cells of water, causing them to collapse, and a high osmotic pressure will inundate them with water, causing the cells to expand. Both results will seriously impact respiration.
[Continued in Part Two, next post]