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Prevent fungus in EI micro mix?

Andy Pierce

Member
Joined
27 Nov 2020
Messages
301
Location
Cambridge, UK
Bit of a weird one, but lately I've been having trouble with fungus/mould growing in my EI micro/trace master mix. This is 1 tsp APFUK "chelated trace" dissolved in 500 ml RO/DI water - this stock solution lasts me about 3 months. I tried making up the micro mix with the addition of 2 ml vinegar (5% acidity) per 500 ml and still got fungus/mould, and then I tried it again with 2 ml vinegar and 1/8 tsp (0.3g) potassium sorbate and still got fungus/mould. I keep the master mix at room temperature in subdued lighting but not total darkness, but the mould/fungus doesn't appear green in any event so I suspect light is not a factor. Help! Anyone else have this type of problem and a good solution?
 

Wookii

Member
Joined
13 Nov 2019
Messages
3,420
Location
Nottingham
You want potassium sorbate:

Amazon product

Add it to your mix water at at a rate of 0.4g per litre before adding salts, and shake well to dissolve (sometimes it won't dissolve very easily if you add it after other salts).

You can also sterilise your bottle with a cap of bleach and water - let it stand for a few hours or overnight, and then rinse and fill.
 
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