If the instructions were to use 2% saline solution then that is what is required. The sterile saline available from the chemist is, as you say, 0.9% which is the same as human blood. It is also called ‘normal’, ‘isotonic’ or ‘physiological’ saline. Used on contact lens to clean and moisten them, it does not hurt the eyes when brought into contact. Having the same osmotic balance as body fluid there is no movement of water or solutes in or out of the eye. A stronger salt solution is used to help disinfect by either drawing water out of pathogen cells by allowing salt ions to pass into it or both. I don’t know which happens with fungal hyphae but I have not got time to look it up. Sea water as an average strength of 3.5% and I sure you would be aware of the effect on your eyes. Table salt is usually pure NaCl and it states if iodine is added. Both rock salt and sea salt are likely to have traces of other minerals, depending on how it is extracted. Irrespective, they are all prepared forhuman consumption and added to a huge number of food products as a flavour enhancer. I don’t think it would particularly hurt the frog ifit drank some 2% saline. It will excrete any unneeded electrolytes as per normal. It copes with the electrolytes in tap water, once the chlorine and chloroamines are removed. A 2% salt solution can be made by adding 20g of NaCl (= 3.6 level teaspoons) to one litre of water. It does not have to be super accurate to be effective. Blue My apologies - I was in a rush. The original solution strength needed was actually 2.5%. That would require 4.5 level teaspoons of salt.