Molybdenum

Trace element essential for nitrogen metabolism in plants and bacteria. Required in microscopic quantities.

Detailed explanation

Molybdenum is a trace element that plays a key role in nitrogen metabolism. The enzyme nitrate reductase, which plants use to convert nitrates into assimilable ammonium, contains molybdenum in its active site.

In aquatic plants, a molybdenum deficiency manifests itself with symptoms similar to nitrogen deficiency: yellowing of old leaves, stunted growth. It's rare because the quantities needed are microscopic.

In marine aquariums molybdenum is present at approximately 10 ug/l in natural water. Its role for corals is not fully understood. Some trace element dosing systems include it but most aquarists do not dose it separately.

Good quality sea salts contain molybdenum in adequate quantities. Regular water changes should keep the level in range.

It is measured only by ICP analysis. An out-of-range value in the ICP usually does not require specific interventions other than a water change and verification of the salt used.

Complete fertilisers for aquatic plants (Tropica, ADA, Seachem) contain molybdenum in the microelement mix. It is never necessary to dose it separately in freshwater aquariums.

Reference values by aquarium type

How it is measured

Only via ICP-OES analysis.

What happens when it is too low

In plants: symptoms similar to nitrogen deficiency. In corals: effects not clearly documented.

What happens when it is too high

Rarely toxic at concentrations found in aquariums.

Related terms