Holtfreter's solution

Holtfreter's solution (Holtfreter's medium) is a balanced salt solution that was developed by the developmental biologist Johannes Holtfreter for studying amphibian embryos and to reduce bacterial infections. As a specialised aqueous solution, it finds use in aquaria to prevent infections for early stage amphibians, where it is typically mixed with soft tap water. Amphibians such as axolotls prefer a hard water solution.

Composition
Molarity of the component salts are as follows: