GH+KH+ mineral

Description

A GH/KH remineraliser raises two things: carbonate hardness (KH) and general hardness (GH), the calcium and magnesium in the water. KH is the half that keeps a biofilter working. The Merck Veterinary Manual gives a working floor for total alkalinity: at or below 50 mg of calcium carbonate per litre, normal biofilter function is inhibited, and the manual says to buffer up to at least 100. That is not an aesthetic target. It is the carbonate the nitrifying bacteria spend while they convert ammonia, and Merck's account of old tank syndrome is what running out looks like from the fish's side. The biofilter consumes bicarbonate, alkalinity falls, and pH slides down gradually enough that nothing looks wrong until it stops being gradual. A tank filled with reverse osmosis water or very soft tap water starts below that floor on day one, which is the case for adding carbonate deliberately rather than hoping. The GH half, calcium and magnesium, is usually aimed at shrimp keepers. FAO's manual for farming the giant river prawn puts ideal total hardness for freshwater prawn grow out at around 50 to 100 mg per litre as calcium carbonate and raises it with gypsum. That is a pond-farmed Macrobrachium, not a Neocaridina in a tank, so read it as a bearing rather than a dose. Buy a remineraliser that publishes its composition, add it to a measured volume, and read the result with a test kit instead of trusting the scoop. Merck's alkalinity floor is the figure to stay above.

Sources

• merckvetmanual.com — https://www.merckvetmanual.com/exotic-and-laboratory-animals/aquarium-fish/management-of-aquarium-fish
• openknowledge.fao.org — https://openknowledge.fao.org/server/api/core/bitstreams/b4d230a3-75b3-45fd-9ebd-7d6ec869ec8a/content/y4100e08.htm

Figures on this page were read off these pages. Manufacturers and databases do change or retire pages; if a link is dead, tell us with the correction link below.