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Asked by marjorie.channon ·January 8, 2021 ·13k readers

Fish hydrolisate has mold on top

I started fish hydrolysate a month ago with fish, water, sugar and lactobacillus from organic Jersey cow yogurt (from a local farmer). The floating bits of fish have gone mouldy. It all smells of yeast/cider/beer/sourdough. Is this okay or not? If not, can I do anything to salvage the liquid?

fish-amino-acid mould

Top answer

From the KNF library

From the KNF library Drafted by Claude from Office Hours and the books · Sep 2026 · 5 sources

Mold on top of fish fuel is not a reason to throw it out. Drake says surface mold is harmless. (Office Hours Ep. 27, 14:37) He also says mold on top is normal and fine, and that fuel needs no KNF medicine or IMO. (Office Hours Ep. 59, 36:05)

Use your nose. Drake eats it himself when it smells sweet, and he calls a good nose the real test. (Office Hours Ep. 27, 34:50)

One office-hours answer gives a pour-off test: if there's no smell and the fish heads aren't floating, pour off the liquid and let the rest keep fermenting. (Office Hours Ep. 19, 41:46) Your floating fish do not pass that test. Drake says floating fish is not a problem once fish has fermented for months. (Office Hours Ep. 53, 26:17) Your batch is one month old.

The library does not cover a yeast, cider or beer smell. It also says nothing about salvaging a batch made with added water.

1 more answer
suze · Feb 2, 2021
When making knfFuel (FAA) from the original recipe with just fish and brown sugar there is a 3-4 day window when you can "salvage" it if its gone wrong. typically the problem is not enough sugar. within 3-4 days of making it if it smells like bad fish adding more sugar can save it. if it goes longer without enough sugar or gets contaminated with water its not salvageable. the amazing thing is that this simple simple recipe of just fish and sugar is chock full of lactobacillus, which is one of the reasons its stores so well for so long. have faith. the microbes will do the rest.

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