Trace elements in sea water

Trace elements - one of the most discussed topics in reef aquariums. Many aquarists have reported positive effects after regularly adding trace element supplements. At the same time, however, there are also horror stories about entire systems crashing. In the following article, you will learn what trace elements are, what role they play in biological systems and what you should definitely bear in mind when adding them. . .

What are trace elements?

The term trace elements refers to elements that only occur in extremely low concentrations in natural seawater. All elements whose concentration is less than 1 mg/l are referred to as trace elements. In addition to trace elements, there are also micro (1-10 mg/l) and macro elements (> 10 mg/l). In marine aquariums, however, all of these elements are sometimes considered trace elements. For example, strontium and boron are usually listed as trace elements even though their concentration is usually over 1 mg/l. So it's all a question of definition.

Where do trace elements occur and what do they do?

Trace elements are important components of biological systems. There they are mainly bound to proteins and enzymes. Enzymes are actually proteins too, but they are actively involved in the execution of biochemical reactions. Without the vital enzymes, it would not be possible to carry out a biochemical reaction under normal conditions. However, the enzymes need specific trace elements to perform this function. They serve the enzymes as so-called catalysts. The trace elements ensure that less energy is needed to start a biochemical reaction.

Trace elements in marine aquaria

Consumption of trace elements in the saltwater aquarium

In closed systems, such as your aquarium, trace elements are consumed due to various biotic and abiotic processes. Trace elements are consumed by the growth of the aquarium inhabitants, absorbed by specific filter materials, removed by the skimmer or deposited in and on the decorative material due to precipitation reactions.

Entry of trace elements in the saltwater aquarium

However, trace elements are not only removed, but also introduced. Trace elements enter your tank through feeding, filling the evaporation water with tap water (note: we generally recommend using osmosis water for this), water changes or the Balling method and the operation of a calcium reactor.

Which trace elements are important for your saltwater aquarium?

The trace elements that are important for you as a saltwater aquarist include: barium (Ba), boron (B), bromine (Br), cadmium (Cd), chromium (Cr), cobalt (Co), fluorine (F), iodine (I), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), silicon (Si), strontium (Sr), vanadium (V) and zinc (Zn). All of these elements play an important role in the biological processes in your aquarium. If their concentration is too low or they are completely missing, deficiency symptoms can appear. You can recognize this, for example, by the fact that your corals no longer grow properly or their polyps no longer open completely.

If corals hardly grow anymore, show a poor polyp pattern or changes in color, these can be signs of a trace element deficiency.

Measuring trace elements - the ICP analysis

Determining trace element concentrations in seawater is extremely difficult and can only be carried out by experienced specialist laboratories. Fortunately, in recent years, some companies have specialized in analyzing water samples from saltwater aquariums and offer this service at a relatively low cost.

Inductively Coupled Plasma (ICP)

The method of choice for determining the trace element concentrations in your saltwater aquarium is the so-called inductively coupled plasma, or ICP for short.

In ICP, a gas, usually argon, is placed in a strong magnetic field and heated there (~ 10,000 °C). This turns the gas particles into ions. The resulting ion gas cloud is now called plasma. If your water sample is placed in this cloud, the particles in it absorb a lot of energy and go into an "excited" state, which only lasts for a short time.

Inductively coupled plasma with optical emission spectrometry (ICP-OES)

The previously absorbed energy is released by the excited particles into the environment in the form of light. Depending on which particle in your sample this light comes from, it has a specific wavelength. With the help of optical sensors, both the different wavelengths and their frequencies can be determined. This is why this special method is also called optical emission spectrometry.

Dosing trace elements - the dose makes the poison

Trace elements do not only have a positive effect on your tank inhabitants. If their concentration is too high, they can cause great damage. In general, this effect is referred to as the dualistic nature of trace elements. If their concentration is too low, negative effects occur, and if their concentration is too high, negative effects also occur. Accordingly, there is an optimal range in which you should keep the concentration of your trace elements.

Regular water changes are very important for the supply of trace elements

In a saltwater aquarium with little to no fish, regular water changes should be sufficient to ensure the supply of trace elements. We recommend a weekly water change of 10%. Only use high-quality sea salt mixtures whose composition has been specially tailored to the requirements of modern saltwater aquariums.

However, if your aquarium is dense or filled with fast-growing SPS corals, it may well be that water changes are no longer sufficient to supply it with trace elements.

What should you do if deficiency symptoms occur?

First of all, you should stay calm, because overzealousness is out of place here. If you suspect that it could actually be a deficiency, you should definitely have an ICP analysis carried out before making any changes.

The ICP analysis will show you whether the concentration of a certain element is too low. If this is the case, most specialist laboratories will also give you instructions on how to proceed to correct the trace element deficiency.

When evaluating your analysis, remember that there are elements (e.g. copper and zinc) whose natural concentrations are below the limit of detection of an ICP-OES. The measuring method simply cannot quantitatively record these low values.

Combination products vs. individual solutions

Combination products are suitable for basic supply in aquariums where water changes alone are no longer sufficient. As a rule, the concentrations of the individual elements in the solution are coordinated in relation to one another, although the manufacturers' recipes can vary. A sensible application is to link the trace element dosage to the calcium consumption. You can find detailed instructions for this in the information text on the Balling method and the trace element solutions from Tropic Marin . If only individual trace elements are deficient, individual solutions are better suited to being able to specifically increase the concentration of an element. Of course, you can also use combination products and individual solutions in combination. In any case, work your way up to the dosage slowly.

In saltwater aquariums with medium to high coral populations, it is recommended to provide the basic supply of trace elements using combination preparations such as the A and K+ Elements from Tropic Marin. Adjustments to individual elements can easily be made.

What should you do if an overdose occurs?

Also, keep calm first! If you are currently using trace element solutions, it is advisable to temporarily stop adding them. The first indication of a possible overdose is the bleaching of your corals. Here too, it is advisable to have a professional ICP analysis carried out. Depending on the results and information provided by the specialist laboratory, you can initiate suitable countermeasures. For example, large water changes or the use of special absorbers and/or activated carbon can help to reduce the concentrations of individual elements. The company Triton also sells a product that was specially developed for the removal of toxic heavy metals: Triton Detox.

What role do nutrients and organic compounds play in the dosage of trace elements?

There are many scientific studies dealing with trace elements, especially in connection with the nutrition of farm animals in agriculture.

These studies have shown that the sole addition of inorganic trace element compounds had no effect on the concentration of the added elements in the blood or tissues of the animals. Only the simultaneous addition of trace elements and organic compounds, such as citric acid or special amino acids, brought success.

In addition, scientists have observed that single-celled algae could only absorb trace elements in the presence of certain nutrients (ammonium, nitrite, nitrate and phosphate).

This provides a first indication that trace elements may only be absorbed by corals in the presence of organic compounds and/or nutrients.

For you as a saltwater aquarist, this means that you can positively support the dosage of trace elements, for example by adding an amino acid preparation. Also, adjust the concentration of nutrients in your aquarium to an appropriate level. They should be very low, but not below the detection limit.

Improving the colors of corals with trace elements - really?

Many experienced aquarists report an increase in the color of their corals after adding trace elements. Unfortunately, there is no scientific evidence for the observed phenomenon. This is also because color is difficult to measure objectively. If you want to try it out, you should be careful when dosing the commercially available trace element solutions. For example, start with half the recommended dosage, observe your animals very closely and monitor the addition with regular ICP analyses. Before you start dosing trace elements to increase the colors of your corals, there are a few things you should consider.

Trace elements are just one aspect that could potentially play an important role in color formation. Much more important, however, is the stability of your water parameters, because corals are extremely sensitive to changes. Therefore, check your water values ​​regularly so that you can intervene early if there are any deviations.

In addition, the nutrient concentrations in your tank should be very low. If they are high, the symbiotic algae of your corals will proliferate rapidly and cover the pigment molecules. This ultimately leads to your corals turning brown.

Another important factor is light. Make sure that your lighting is strong enough and has a high blue content. The strength of the light, i.e. its intensity, can be determined using a PAR meter. Your lighting should provide you with PAR values ​​that are on average in the range of 250 µmol/m ² /s.

And now for the most important point: patience. Always make changes slowly and give your corals time to adapt to the changes.