Nutrients and Trace Elements
Although general hardness, buffering capacity, pH and salinity of water are the most important properties of water, tap water also contains minerals and trace elements in very low concentrations. Some elements are produced by fish metabolism, such as nitrates, the end product of the nitrogen cycle. Phosphates may be present in fish food or even in tap water. Phosphates have been linked to algae growth. There are other trace elements necessary to guppy metabolism, as indicated in the Guppy Nutrition Table (in the Nutrition chapter). Frequent water changes help restore trace elements consumed by guppy metabolic processes. You can also purchase so-called mineral supplements or trace restorers, but these are not necessary if you feed your guppies a wide variety of foods.
Dissolved oxygen is absorbed into the guppy’s bloodstream through the gills. Oxygen enters water at the surface. Water needs to be circulated in the aquarium to maximize the gas exchange that occurs at the surface. Some guppy keepers have two box or corner filters in the tank running at very high air pressure to turn over the water as quickly as possible. Power filters tend to do a better job at water circulation as they move more water and do a better job of breaking up the surface. In nature waves and wind facilitate gas exchange on surface waters. The aquarist tries to mimic this action.
Guppies optimally require a concentration of 5 parts per million (ppm) of dissolved oxygen in the tank. At concentrations below 2 ppm, fish become extremely stressed. At concentrations below 1 ppm they begin to die. Oxygen Depletion
There are a number of factors that cause the oxygen levels in the aquarium to drop.
Plants and algae consume oxygen in the dark. Plants and algae only consume O2 at night, during daylight hours they use CO2 and expel O2. Bacteria consume oxygen. These bacteria multiply in the presence of fish waste and the decay of organic matter (such as dying plants). Aerobic bacteria consume O2. Anaerobic bacteria (or bacteria that grows in the absence of O2) are extremely dangerous, that’s why you shouldn’t use gravel in your breeding tanks. Stratification of the tank due to inadequate or faulty water circulation.
Certain chemicals, such as formalin, oxidize, removing oxygen from the water.
As the temperature rises, the water is less capable of holding oxygen in solution. Water at 90°F (32°C) holds only 7.4 ppm dissolved oxygen. At 45°F (7°C) water can hold 11.9 ppm dissolved oxygen. At the higher temperatures fish metabolism increases, increasing the demand for oxygen.
Suspect low levels of dissolved oxygen in your tanks if the fish suddenly stop feeding, all die at once or they are at surface of the water gulping for air. In larger bodies of water the water will turn dark in color and give off a putrid odor. There are electronic oxygen meters available, but they are too expensive to make them practical. Check prices at aquaculture supply companies, or web sites serving pond keepers.
Salinity refers to the total amount of dissolved substances in the water, including those affecting GH and KH. Sodium is not measured by GH and KH, but it is included in salinity. Sodium is table salt’s main component.
Sodium is not normally added to fresh water aquariums, but many guppy breeders add salt to their aquariums as a disease preventive and to help the guppy osmoregulatory system. Salt can stimulate production of the guppy’s slime coating, a first defense against the invasion of pathogens. One tablespoon of salt per five gallons of water helps prevent the invasion of the parasite ich (Ichthyopthirius multifilis), and other parasitic infections.
A hydrometer is required to measure the amount of salt in an aquarium. It is used to find the ratio of a solution’s weight to the weight of distilled water. It’s not an instrument usually found in a guppy room, as guppy breeders use very little salt in their aquariums.
Add one teaspoon of salt per gallon, or one tablespoon for five gallons. Almost any salt will do. Some people do not like to use salts with additives or table salt because it uses anti-caking agents like iodine. However these additives are in such minute quantities that they are not harmful to guppies.
Philip Shaddock: I use one tablespoon of aquarium salt for every 10 gallons. It has mild anti-parasitic advantages at this concentration and adds a bit of time to the life of live brine shrimp.
Consider using the following types of salt, in this order: sea salt, water softener salt, rock salt, Kosher salt, non-iodized salt, aquarium salt, plain salt, table salt. Aquarium salt and table salt are at the end of the list merely because they are relatively expensive.
Salt does not evaporate so do not add it when topping up an aquarium low on water. When doing water changes reduce the amount of salt added to compensate for evaporated water. Occasionally reduce the recommended amount to avoid salt build-up.