Backyard Aquaponics
A place to discuss aquaponics

geez mate, they were in good nick. What a bummer. Interesting about barra needing purging for 2 wks. I wonder why, they have such a high metabolism.

theres an old saying in the aquacultural industry.

your not an aquaculturalist until you've lost a million fish. i have a few more to go yet.

i found the 2 week purge thing interesting as well. i would have thought a couple of days but apparently thats not long enough.

i seem to recall that purging isn't just to remove gut content but also bacteria and types of algae in the body. these are what give the fish the off flavor more so then gut content.

You don't purge them when you catch them from the ocean and I would have thought aquaponic tank water is well filtered and fairly clean.

I purge my fish high density and they don't seem to stress - though this is the perch.

It's not the water Faye, but the pellets. Fish feed makes nasty meat imho, a fast cleans up their system heaps, and any dirt that may be there

and from what i recall types of algae and bacteria which can build up in tanks.

how long are you purging for vb?

cheers

2 weeks sounds like an overkill to me for Barra. The off flavours in cultured fish are generally worse in fish with a high fat content like Silver Perch and most farmers generally only purge them for 7 - 10 days for pond reared fish.
As the off flavours originate from algaes, like Faye I wonder if they are present in an aquaponics system and maybe only a couple of days purging to empty the gut content is all that is required.
Faye you have eaten Barra from your system havent you??
How did they taste and did you purge them??

A couple of points:

1. I agree that the pellets are likely to result in some poor flavour. I came to this conclusion when I caught a fish for weighing and photographing at one point and it shat in the container. I was silly enough to put my finger in said shit and bring finger to nose for a smell. Was as bad if not worse than any pellet fed chook shit I've smelt (and that's pretty bad). Despite washing with soap - my finger smelt for a while after that.

2. Early on I did eat one perch straight out of my system - no purging. It had no noticable tainted taste. It is important to note however that at that point the fish had not really fed for a few weeks, because it was too cold.

3. The periods I have purged my fish for vary. I would normally look at purging for at least 5 days (in saline water). I do however often purge for a lot longer than this, simply because I like to catch a few fish at once and will then only slaughter them when I want them. Because perch have a big build up of fat in their guts to get them through leaner times, I could potentially purge for months wihout killing the fish. The longes I have had a fish purging for is probably about 3 weeks and the 4 I have left in the purge tank right now must be gettign close to that also.

Dumb question... Why Purge? When I take freshwater fish from rivers and lakes I cut immediately and eat... no purging?

Boyd, the third post on this page asks the same question, almost exactly... perhaps have a read again of the last few posts.

i have eaten one of the four barra I got to a good size and this was done merely by not feeding them for about 5 days.

THis worked I think because the plants take out the nitrates and there was some thought a while bakc on here that the nitrates contributed strongly to the off flavour.

This fish tasted the best I have eaten and was beautiful.

Nice Stats Nick, Thanks for the info.
Can somebody with multiple tanks test by not feeding one tank but keeping the nitrates up by feeding other fish tank? I'd like to know if it's the pellets only or whether 'clean' water needs to be used for purging.

Also TT if you're reading... how did purging in salt solution taste? Or have you not done that yet?

thanks for the posts peeps.



this would make sense if algae does in fact contribute to off flavors. less nitrates= less algae and perhaps less off flavors.

i guess a couple of my own trials are in order. i'll harvest a fish over a period of up to 4 weeks without feed. i'll take one everyday and see for myself if there is much of a difference. ap fish may well not require a long purge.

i'll hopefully find out.

i guess every system is different and we need to find the best method for our situation.

the beauty of purging in the system is that shock is minimized. if you harvest them all at the same time you can then simply drain the tank and chuck in some ice.

i have a feeling that there is good bacteria and bad bacteria. bad bacteria makes the fish taste foul, where as good bacteria gives a fish more flavor. i reckon theres more good bacteria in ap systems then sterile aquaculture ones. perhaps for this reason fish grown in ap systems or even ponds require less purging. then of course theres less algae.

who knows?

Haven't harvested any yet KP, salt is purely precautionary atm, what with the heat and all.