Backyard Aquaponics
A place to discuss aquaponics

hi guys im doing some work experience at a fish farm and the farm manager is a knowledgeable dude. told me today that the "off" taste of fish from fresh water, (notoriously carp) is due to a bacteria under the skin.

What wikipedia says about geosmin:

Effects

Geosmin is responsible for the earthy taste of beets and a contributor to the strong scent that occurs in the air when rain falls after a dry spell of weather (petrichor) or when soil is disturbed.[5] The human nose is extremely sensitive to geosmin and is able to detect it at concentrations as low as 5 parts per trillion.[6]
Geosmin is also responsible for the muddy smell in bottom-dwelling freshwater fish such as carp and catfish. Cyanobacteria produce geosmin and 2-methylisoborneol, which concentrate in the skin and dark muscle tissue. Geosmin breaks down in acid conditions; hence vinegar and other acidic ingredients in fish recipes help reduce the muddy flavor.
[edit]

He also said that

The geosmin producing bacteria can't tolerate salt, and will be purged to indetectable levels at 5-6 ppt with 48 hours.

You guys might know know this already, but hey it was fun to know the science for me at least.

Cheers!

Thanks for that moekuc

Valuable information indeed....and it totally makes sense why after purging a catch of yabbies in salt water makes the flavour a whole lot better.

My last batch of Barra (18) I salted to 6ppt and never fed for a week before I culled them. Have tried 3 lots now and no muddy flavour. Did watch a U-Tube clip the other day about commercial farm in USA and he salts to 10ppt for a few days.

I'd be interested in your JADES and if you think they too need a salt purge before eating. Can't hurt the flavour I guess to give them a few days in a salt bath!

My jades were great and no purging or salting

Interesting stuff Moekuc , good work

you wont necessarily get the same bacteria in AP so it makes sense. Its slime type algae type thingie lol.

err, looks like pondscum/algae but its bacteria. it photo synthesizes too.

http://ks.water.usgs.gov/studies/qw/cya ... ake-ia.jpg

in an AP system algae and cyano can't really reproduce because it is out favored by shading and letting the available nutrients be taken up by plants. In a pond, they make up the basis of the food chain for the lower order organisms.