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.^[1] 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.^[2][3] Amphibians such as axolotls prefer a hard water solution.^{[citation needed]}

Composition

Molarity of the component salts are as follows:

NaCl	0.059 M
KCl	0.00067 M
CaCl2	0.00076 M
NaHCO3	0.0024 M