Backyard Aquaponics
A place to discuss aquaponics

also if you look at earthbounds blue barrel system he has done subsurface overflows and this is because the current of removing water from below the surface will not disturb the duckweed at the surface. this is not very well explained but have a look and you can see what I am talking about.

$30 for Barrels? Ohhhhh..... Keep shopping around, mine were $12 each and had had phosphoric acid in them, which is fine, you get that in coke... Acids are no problem at all because there are no residues and they are washed out by water...

You were looking closely at my pics Nick..... It's actually at the surface, with the guard around the outlet to keep out the duckweed..

$12!!! I think i got mine for 20........maybe you had bargaining power with quatity EB

Na..... salvage yards.... And check out the local trading post type paper, this is where I got the current supplier from, he works for a chemical company and makes cash on the side..

what cash economy???

Hi,

On the matter of drying duckweed, you can.....but the the big question is.....Why?

The real attraction of duckweed is that anyone can grow it.....if they are prepared to emulate the conditions needed for optimum production.

Like every plant on the planet, duckweed has a preferred temperature, humidity, stocking density, pH, daylength, light intensity and nutrient mix.

Duckweed production on a small scale is a turnkey operation.....it's the simplest form of hydroponics. It's the quintessential hydroponic fodder.

You should be able to tailor production exactly to suit your needs.

It necessarily follows that if you supply optimum conditions, you will experience optimum growth.

We know from the research that duckweed can reproduce its own weight every 24 - 48 hours. It's also capable of growing at the rate of 1kg per square metre before it begins to self-mulch.

Let's assume that we create a pond with an area of 3 square metres. Allowing a margin for error, that should (assuming that everything else is right) allow us to produce 1kg per day.

That's a lot of duckweed for your fish.

Growing duckweed is no different to growing fish. You have to manage the growing parameters. The closer the management, the better the growing performance of your fish.....or duckweed.

if we ignore the pH, oxygen levels, temperature and nitrate levels for our fish they'll fail to prosper........or die. It's the same for the duckweed?

My advice is to scale your duckweed production down to a level where you can control every parameter and achieve optimum growth. Then you can replicate the growing conditions....and proportionate growth.....on a larger scale.

The main reasons for feeding fresh (undried) duckweed include:

- maximum vitamin and mineral content.
- minimum labour input......scoop it out of the pond and into the fish tank - it doesn't get any easier than that.
- palatability - given the choice, most animals prefer fresh food.
- minimal cost of production.......every time you apply resources (labour, electricity, etc) the cost of production increases.

Gary

I bought 2 buckets today just for growing duckweed - but I will wait for summer before I try - or perhaps I should half bury them in the compost heap to warm the water... hmmmm

Gary - in simple terms what are the optimum growing conditions?

VB, you beat me to it.

Gary If you could post that under "optimum duckweed conditions" topic (just create a new one under plants) that would be great. Otherwise some poor person will have to navigate though 7 pages of duckweed for the best conditions

Thanks

Steve

It is so great to have you back on the air 'Mr Duckweed'...

So assuming that you can grow 1kg per 3 sqm. I have a duckweed growing area of around 7-8sqm, so perhaps 2kg per day allowing lots of 'scotts' factor. Duckweed is 95-98% water was it? lets say 95%.

So that would be the equilalent of 100g of dried duckweed, the reason for working this out is because I knew that dried duck weed is about 40% protein.. 40% protein is about the same as the feed I am feeding my fish at the moment therefore. Fish need 1-4% of their mass in feed each day, as a good growth rate for feeding.. this is good fish feed for 10kg of fish.........

I don't know if I've got the sums right there, should go to bed and look at it in the morning...

I read this forum before setting up my system.

I prepared my ponds, establishing duckweed before I put the perch in.

I added perch, then offered them fish flakes. They ignored the flakes, they eat the duckweed.

I guess they will eat the flakes when they are ready - but it looks like duckweed is going to make up a good % of their food. A good, cheap option, and the fish prefer it!

Be a bit careful before you decide to feed your fish nothing but duckweed. I doubt if it's a balanced diet for most fish.

Many diets will keep something alive but if you want to realise the full growth potential of any species you have to meet its dietary requirements pretty closely.

As a general guide, most livestock rations contain plant protein (lucerne meal, soybean meal) animal protein (meat, bone, blood, fish meal) and grain in varying proportions. Different feed ingredients contain particular vitamins and amino acids - a lack of some of these can have quite devastating outcomes.

I'll try to obtain a comprehensive analysis of duckweed and then measure that against the dietary needs of Silver Perch (for example). That should help me to arrive at whatever is missing in the straight duckweed.

Monya, I saw that your question about yabbies (and whether they'd eat duckweed that had died and sunk to the bottom) went unanswered so I thought I'd have a go.

Yabbies eat virtually anything preferably once its well rotted or has gone through the guts of something else first. This rotted material is called detritus. It generally lies on the bottom of the pond. Your duckweed will eventually become detritus along with any other uneaten food and any solid fish poop. When people go fishing for yabbies, they often use rotten meat, rabbits' heads and the like. Some of them even bait their cages with bars of hard soap.

Of course, if you want to grow yabbies quickly, it will pay to find out what their optimum diet looks like and make it up accordingly.

Thanks Gary

Yes, haven't yet but have been wanting to put a "duckweed corral" on the surface of the fish tub. I'm thinking a perimeter of styrofoam, and some underwater flat barrier to keep the fish from eating it. There will be a smallish slot/hole in the perimeter. When they've multiplied enough, they will push some of their neighbors out of the corral to be eaten by the fish, otherwise they stay in the corral nice and safe and multiply. Kind of like a duckweed supply feeder (versus a demand feeder).

The ice cream container way would be to put a small slot in the perimeter, and leave the bottom on with some small holes for drainage/circulation.

I have been feeding my precious little duckweeds on worm tea, but they seem to be dieing off - thought this would be good for them - I need to try something different like the cow poo idea before I lose my last weed, or is there something else I could try?