Backyard Aquaponics
A place to discuss aquaponics

As Aquaponics and Aquaculture become more mainstream, there will be an increased demand on fishmeal based feeds which is already becoming costly both environmentally and monetarily. Increased plant based feeds are being added to meal, but often lack long chain Omega 3's. Short chain O-3s are found in quite a lot of plants such as brassicas and some halophytes, but long chain fatty acids are better.
How do we growers boost the long chain fatty acids in our fish and do it sustainably?
I know CSIRO are developing Omega 3 Canola with 12% long chain fatty acids which may become the main method to replace fishmeal, but it is not yet available commercially and is obviously GMO.
I considered purslane to feed my SP's, but Dangerous Dave in Nth NSW has found that his SP's and Jades don't like it.
So, anyone having success with Spirulina or some other O-3 source that they would like to tell us about?

The obvious one is Azolla

Messy stuff to grow

I use a bit (Free out the river) for the chooks , and duck weed through the summer

No doubt big shallow pond / trays it would grow

If it is water sustainable is a whole different subject

http://theazollafoundation.org/azollas- ... tock-feed/

long chain omega 3s in freshwater fish is a subject I am very interested in!

Certain freshwater fish are believed to be pretty efficient converters of shorter chain omega 3s.

http://www.fao.org/in-action/globefish/ ... /c/338773/

The above link describes how Carp provide the bulk of long chain omega 3s (DHA and EPA) for human consumption globally, while only using a tiny proportion of global fish oil supplies (aka long chain fatty acids from wild). This is testament to the carps ability to convert/elongate the omega 3s.

Flax and Chia are sources of shorter chain omega 3s with (according to wiki, though an expert in the field once told me otherwise) a desirable omega 3-6 ratio. Therefore farming carp with the introduction of flax, chia, etc, would be a way of producing DHA and EPA without relying of marine resources.

I have also thought about the potential implications for predatory species raised in poly-culture with efficient omega 3 elongater species. For example, Redfin/european perch, which are predatory and supposedly good omega 3 converters themselves, could be reared along side carp. The fish would be fed a flax-seed based diet, the perch would eat a combination of this feed and small carp, and would perhaps accumulate respectable levels of DHA and EPA?

Basically, if poly-culture was practised using as many efficient omega 3 converters in as many trophic levels as possible, all fed on feed rich in short chain omega 3s, would the long chain omega 3s bio-accumulate up the food chain resulting in increased DHA and EPA in the predatory fish?

I've been feeding jade and silver perch to friends and family with the advice that they have higher levels of the good oils than sardines. Would hate to find out I was spreading false news!

Above belief was partly based on material at the Ausyfish website... after I bought perch fingerlings there a couple of years back. There's quite a detailed write up on Omega 3 and reference to CSIRO research (though not sure if the short vs long chain distinction was made).

Maybe the quoted naturally high levels in perch are on their wild diets only.

Will follow this thread with interest. But the perch taste pretty good out of the smoker regardless.

I remember a paper a few years ago about lupins providing an almost complete feed for fish including omega 3. can't remember precisely if it was short of long chains...

Lots more investigation and I am now planning 2 ways to boost long chain Omega 3 fatty acids in my fish.

1. I am fortunate to have ample supplies nearby of Ulva lactuca (sea lettuce). A recent study of DHA and EPA in 6 Australian seaweeds found only Ulva lactuca had appreciable amounts of DHA.

2. I am setting up a microalgal bioreactor to grow Spirulina, which is high in EPA. I am using an LED 12V light strip inside a foam fruit box and 140micron plastic liner. Don't know if tis will work, but I'll see how it goes.

I will try to mix these together and use them as a supplement to the Skrettings.
(My fish like Ulva fresh, but seem to be strangely sh!t scared of any red algae I have added to the tanks).

Sounds like an interesting project!

I believe flax, chia and insects have alpha-linolenic acid, a longish chain fatty acid, which freshwater fish convert into DHA and EPA.

It would be interesting to know the rate and efficiency of this conversion for different freshwater species. I think i've read somewhere that salmonids do this to an extent but other fish like red-fin perch and carp do it better...

Anyone heard anything like this about other species?

Danny, from what I've read, fish can convert ALA into longer chain Omega 3's but at very minimal levels (I read of only 1-2%), but this was only for Salmonids.
I will keep my eyes open for conversion ratios in other fish.

Also, Danny, your suggestion re bioaccumulation is interesting. Most of eastern Australia has very healthy populations of glass shrimp which feed on detritus and algae and are the main natural food of most Australian fish including SPs. They are very prolific breeders and fast growers as well as being pretty tough regarding water parameters. These might work better here than carp as you suggested. I don't know if you have something similar there in the UK, but I suspect you probably do. (I have no idea as to their ability to bioconvert ALA to longer chain fatty acids though. Perhaps this will be something to try further down the track because of their quick growth/fecundity).

Thanks, this is a fascinating discussion. I'm following along and reading these links you all are posting. Funny about how the fish are scared of Red Algae. Of course I had to look it up being land locked here in New Mexico https://en.wikipedia.org/wiki/Red_algaeI guess it is kind of scary looking!

Really informative thread.

No matter what the fish is, it is obvious that we need to provide a diverse diet with worms, maggots, water plants, shrimp, gambusia fish etc.

I have an empty large aquarium and planning to get my son into glass shrimps, that would be one source of live food for my trout.

I have BSFL in summer and red compost worms.

I also have a styrofoam box of night crawler worms in home. I started this recently. They like to have a stroll around the house and dry up on the carpet which then fed to fish. Nothing is wasted

Yeah, given that bio-accumulation is how fish like salmon and tuna end up with so much DHA and EPA in the marine environment one would have thought that the same might occur in freshwater. Of course, as you point out the lower links of the food chain and their omega 3 elongation capacity would be great to know! I think there are a kind of glass shrimp in Europe, but only really found in tidal zones. Then there are gammarids which are fully freshwater and are a key feed source for wild trout and (european) perch etc. I have read a study somewhere which found decent levels of DHA and EPA in gammarids.

Freshwater bivalves may also elongate omega 3s...


There is a fascinating aquaculture project called Veta la Palma. For those interested i suggest taking a look, there are a couple of videos on youtube.

This is an extensive fish farm in tidal ponds based in Southern Spain, and the algae and glass shrimp form the basis of the primary production. No feed, no chemicals.

Danny, was it gammarus pulex mentioned in a study? Do you have a link?

Gurkan, actually the ponto-caspian species, originating from the Caspian sea, are the richest in DHA and EPA. G. pulex has more of the Alpha-linolenic acid. I think all gammarids are are good protein sources but the really good ones in terms of Omega 3s are the ponto-caspian ones. Heres a link to an article.

http://invertebrates.uni.lodz.pl/wp-con ... 0acids.pdf

Thanks for the link Danny.

I wonder if there is a commercial producer of these shrimps. It looks promising.