What are they?
Trace elements refers to a collection of tiny amounts of chemicals which are required by aquatic plants or animals to grow well and remain healthy.
Most trace elements are provided by the slow dissolving of minerals by pebbles and rocks in the substrate and by the addition of food and via the decay of fish waste as well as by decaying plants and bogwood.
However fish food, substrate products, etc. typically will not tell you what is in them in any detail and so the aquarist is left in ignorance as to their presence in the water. Whilst some test kits do exist to allow you to test for a few of the chemicals like iron, copper or potassium, these can be expensive and are often not available on sale at your average fish shop.
Trace elements for plants
Scientists often argue about the exact chemicals that plants require. This is mainly due to the vast number of plants that an aquarist could place in their aquarium and the scant amount of research done for a particular plant in the aquarium trade.
But the list below is a typical example from a supplier selling trace element powder for your average aquatic plant. Though some of them can be found in fish food.
|Elements||Nutrient Form||Quantity||Supplied via...|
|B (boron)||BO33-||Trace||Fish food, PMDD|
|Cl (chlorine)||Cl-||Trace||Fish food|
|Cu (copper)||Cu2+||Trace||Fish food, PMDD|
|Fe (iron)||Fe2+,Fe3+||Trace||Fish food, PMDD|
|Mn (manganese)||Mn2+||Trace||Fish food, PMDD|
|Mo (molybdenum)||MoO42-||Trace||Fish food, PMDD|
|Ni (nickel)||Ni2+||Trace||Fish food|
|Zn (zinc)||Zn2+||Trace||Fish food, Fertiliser|
- See Plant nutrients for more details and a complete list of nutrients.
Trace elements for fish
Fish need trace elements in their diet to have a healthy fully functioning immune system. This can be provided by a good quality varied diet. (Aquarists often advise giving your fish 3 or 4 different types of food a month to ensure that the animal gets all its required minerals).
Whilst there is a lot of data on commercially exploited fish, there is little information on the vast range of fish sold in the ornamental fish trade. But it is reasonable to assume that the basic range of chemicals for the fish above would apply to other fish from similar eco-systems.
Amino acids - Arginine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine + tyrosine, Threonine, Tryptophan, Valine
Fatty acids - n-3 & n-6
Microminerals - Copper, Iodine, Iron, Manganese, Zinc, Selenium, Fluorine
Fat-soluble vitamins - A, D, E, K
Water-soluble vitamins - Ribolfavin, Pantothenic acid, Niacin, Vitamin B12, Choline, Biotin, Folate, Thiamin, Vitamin B6, Myoinsitol, Vitamin C
Macrominerals - Calcium, Chlorine, Magnesium, Phosphorus, Potassium, Sodium
- These chemicals were copied from the Nutrient Requirements of Fish, National Academy of Sciences, pp. 16-21,1993.
- This is why it is important to do regular water changes in a typical aquarium set-up as tap water naturally contains most of the trace chemicals and as they are used up by plants and your animals they will need replacing.
- The Walstad tank is one type of aquarium set-up that needs little water changes as the soil in the tank provides most of the trace and macro minerals required for the plants and fish.
Few people bother to look up and obtain their free tap water suppliers water report to see if these trace elements are in their tap or well water. Plus due to the inability to test (cheaply) for the presence of most of these in tap water (or in fish food), we often have no idea if the fish are getting their necessary minerals to remain healthy.
Also many aquarium substrates on sale are either total artificial (some are coated in plastic) or the pebbles are chosen not to dissolve in water so as not to effect the chemistry of the water. This is an important consideration. But the side effect of this is that there may be the risk that the fish do not get all the trace elements they need and their health may suffer.
Also several fish companies now sell products that claim to make your aquarium water more like its natural environment (typically called blackwater). They supply a liquid bottle with chemicals in it that you regularly add to your tank to help simulate the chemicals found in the Amazon river in South America for example.
Typical chemical products:
- TetraAqua - Blackwater Extract
- Kordon - VitaTrace : Freshwater Trace Element and Vitamin Supplement
- JBL - Tropol tropical black water conditioner
- Seachem - Cichlid Trace
- Seachem - Fresh Trace (General Tropical fish)
- Seachem - Discus Trace
- Seachem - Gold Trace (Goldfish)
- Trace Elements by Timothy A. Hovanec, Ph.D. (archived link May 2007)
- Nutrient Requirements of Fish, National Academy of Sciences, pp. 16-21,1993. (Nutrient Requirements for Channel Catfish, Rainbow Trout, Pacific Salmon, Common Carp, and Tilapia as Percentages of Diet) (Amazon)