Hello Juan, you can pre-mix the ingredients minus agar and preserve by refrigeration (4 deg C), although I think their concentrations are a bit high for a basal medium. Anytime you want to make use of it you measure the appropriate volume and solidify with 1.5% agar-agar and sterilize by autoclaving (your 2% w/v is alright for the activity screening). Care must be taken during mixing especially with ferrous salt as component. It has a tendency to precipitate. Try warming the distilled water meant for the mixture to about 45 deg C before adding the ferrous salt. Even though you didn't state your units correctly, I presume they are in g/L. If so, then I think the composition of iron at 0.1 g is too high. If I might suggest, please leave it at 0.01-0.001 g/L. Cheers!

What fungus are you using? Many require cofactor supplementation.

Thanks @Maurice Ekpenyong for the valuable tips, and well the composition is stated on the method I'm using (AATCC 30-2017) and it is indeed in g/L, sorry, I forgot to mention, but I will make great use of your advice to mix the salts. So far I've only found one brand offering this agar pre-formulated but it isn't sold everywhere.

@Phil Geis I'm using Chaetomium globosum and Aspergillus niger

Hi,its depended on types of fungus.