Backyard Aquaponics
A place to discuss aquaponics

Ok, I keep hearing that you can only raise fish using commercial fish feed so I have conducted a little experiment. I took two small fish from my newest tilapia. On had its tail eaten off when I received it, so I placed it in a 20 gallon aquarium with only algae. No food or air was added. The other fish was healthy and placed into a tank and fed commercial fish feed with 32% protein. Here are the results over the past month.

Both fish have doubled in size.
Both fish weigh 4 Grams
The Fish fed Commercial feed is just a little longer.
The Algae fed fish re grew its tail and looks very healthy.
The Algae fed fish looks less stressed. Because of no competing fish I guess.

I'm not going to argue your results,,,but could they possibly be repeated with smaller fish and the use (recommended) o f45 - 50% protein flake.

One of the huge benefits of the availability of Tilapia Dandi.... they're algael feeders by nature and will grow quite happily on a algael diet...

As Chappo suggests though, in commercial operations it's been found that high protein feed enhances early growth....

And more particularly, (correct me if I'm wrong Chappo) greatly improves growth at latter stages of development compared to a purely algael diet...

Dan, I think most of us talk about and use commercial feed is that it is readily available in qty to regularly feed it to the fish - algae, duckweed, BSF and greens (lettuce leaves) cannot be sustained over an extended period... (maybe cannot is too harsh a word)

Okay, so now we see the sopwith in a vertical dive heading for mother earth

Funny you should say that Les....

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Here about 12 months ago i decommishioned the duckweed tank i had a few silvers in there for mozzie controll caught the silvers [i thought] and put them in the system and left the tank to its own means[ no air no top up nothing ] it 1/2 evaperated away would have been stinking hot [over summer] went green then slymie had leaves twigs in it ect [you know what i mean ]When i went to clean it out [for the trout] pumped it on the dirt garden got it down to 1 1/2 deep and there was movement one lone silver the healthiest fish you have seen 8 in long

I think, so far, the growth rate is just fine for home food production. The only question I would have is how much algae would it take to feed a pound of fish and how much water would be required to grow it? With large enough algae ponds it would be possible to feed only algae.

If you must buy commercial feed, why not just buy textured vegetable protein and eat it instead of fish? It would be cheaper and simpler; though not as tasty. In my continuous production system with 80 pounds of fish in it I would require 864 pounds of fish feed per year; feeding 3% body weight.(that seems like a lot of feed for 360 fish per year, what is the tilapia feed conversion rate?) At about $17 per 40 pound sack of catfish food I would spend $367.20 of fish food (at current prices) for 360 fish that hopefully weigh a pound or more; about $1.02 per pound of fish and I would still not know how much mercury and lead would be in the fish flesh the feed is made from.

Now, I understand that most home growers have to work and dont have time to devote to collecting food for fish all day, but what about a retired person who has loads of time?

Dan,

I have been told some tilipia farmers use 'super phosphate' to encourage algae growth and put the young fish into the algae bloom ponds.

I see no reason one could not grow the algae and measure the density, and therefore food value, by opacity. One would then pump (using a proper pump capable of handling the algae) an amount to provide the correct quantity of material to the fish pond.

If one got really elaborate, the micro-processor could be used to measure the opacity, calculate time of pumping, initiate pumping and automatic shut-off. Even more duties could be assigned by measuring the opacity of the 'fed' pond and see if all of the algae or the correct percentage is consumed between feedings. Even more duties could be added to the little chip and have it calculate how much phosphate needed to be added to the algae pond for maximum algae growth!

One thing left is to build an automatic measurer and counter where the fish weight would be calculated......

Ron

I am going to give it a try! Measuring the light that is passing through the water will be simple with a vertical algae setup. I just have to get some clear PVC pond liner or other UV stable material that I can heat weld or glue to look like this:

...use all that spare time keeping the missus happy

A number of chemical and natural fertilisers are used to create/control the algal bloom,,,a lot depends on water chemistry /soil make-up etc,,but super-phosphate is what we have used in conjunction with chicken manure. Algal bloom is measured with a Sechi disc,,fairly simple ..... watch out for early morning low oxygen problems.We hang the fertiliser in bags , if sechi disc readings get a bit hi,,we lift the bags out for a few days,,,if the bloom is allowed to get toooo dense,,,then you get an algal BOOM- CRASH ,sudden HUGE oxygen demand and result - lots of floating dead fish.
It's not that difficult to control but what this bloom will do to other parts of the AP system I can only guess.
Rupert is correct about young tilapia needing a good "childhood" and "teenage years",,high protein diet.Get them started fast on 45% protein powder ( 3 or four feeds totally 10% body weight), then 45% protein SMALL pellets( 3 feeds totally 7% body weight) until maybe 4 inches long,, then convert to 30% pellets( 2 feeds per day totalling 3% body weight) is ok .
Our smallest ponds are 800 square metres , using algae only would restrict stocking to 200 fish per pond,,using good pellets and algae as an extra , we stock at 2,000 in these ponds. ( additional cost is some early morning aeration).
All -up I'd guess , in an AP system it will cause more problems than it's worth,,,but it is definately worth a try.
I'll watch with interest.
Cheers

Chappo.. do you drain harvest your ponds... then dry and add lime???

For those who may not know the basis of blue-green algael bloom pond cultures...

The objective in liming is to correct the acidity of mud at the bottom of the pond,

Liming increases the effectiveness of fertilizers added to the pond ...(ie. super-phosphate, or chicken poop).....by making more of the phosphorus available for plant use.

Lime also increases the alkalinity of water which increases the availability of carbon dioxide for photosynthesis.

The increased availability of phosphorus and carbon dioxide will, in turn, increase populations of phytoplankton (microscopic plants) which will promote larger populations of zooplankton (microscopic animals).

Both phytoplanktonand zooplankton are important food for fish.

The addition of lime helps guard against daily pH (acid level) fluctuations that are common in ponds with dense populations of aquatic plants.

Lime can also improve the effectiveness of many herbicides used to control aquatic weeds, and in addition may also prevent some fish from being killed by these herbicides, as some of these chemicals are more toxic in soft acidic waters.

N.B as Chappo noted..

Quote:

if the bloom is allowed to get toooo dense,,,then you get an algal BOOM- CRASH ,sudden HUGE oxygen demand and result - lots of floating dead fish.

Blue-green algael bloom management is somewhat an art, best practise requires a COMPLETE understanding of the systems/processes involved....DAILY monitoring (2-3 times).... and the ability to add additonal aeration at a moments notice...

And that's in 1/2 hectare ponds..... usefulness in AP systems with small volumes of water..... just not worth the risk IMHO....

There's enough algae attached to the tank walls to supplement fish needs in an AP recirc tank environment IMHO.... and you can always supplement feed lagael or spirulina wafers/disks if you feel the need...

Yes on the pump out harvest and lime ( done each second harvest / yearly).
The drying out and liming aslo get's rid of any baby "predator" fish and helps with desease provention.

All good info! Thanks guys! What I have in mind is growing stringy algae in a separate system and then feeding the algae to the fish; either wet or dried in a solar hot house. My fish tanks are not in sunlight. So I will add only what they seem to eat right away. I am going to give a try. If all I can do is supplement then so be it.. I could also use my extra chicken eggs as a protein source; not sure what the % of protein in an egg is..


Do either of you know where I can buy a large bulk of algae disk in the US? And what about algae powder? Will the fish strain it from the water?

Dan,,love the idea,,,vertical frames might just be the answer.
i've been playing with a siliar frame idea for Azzolia/duck-weed.

Making it economically viable is not easy.