|View across duckweed ponds|
We hired a backhoe and a driver to dig our lakes which were 30 m long by 2 m wide (98' x 6.5'). We then put clay down and lined them with a plastic liner. These are shallow, only about 2' deep.
|Clay lined duckweed pond|
As you can see these take a bit of organising but in the end, they aren't that difficult to create. If you were to build them there are a few things to keep in mind.
The liner is crucial. Here we had to take several things into consideration.
- Ability to cope in extreme UV conditions. (we have over 300 days of sun a year and more often than not our level of UV (Ultraviolet light) is in the extreme category. Your local weather forecast can help you determine what your UV index is for your area.
- Non-leaching. We had to make sure that no toxic or unpleasant chemicals would leach into the water which could cause problems for the duckweed and subsequently the fish.
- Robust. We had to have a strong plastic liner. Often bits of twigs might end up in there. Also we have chickens. We needed something that was tough enough to resist being damaged.
|Various stage of completion|
|Overflow system for duckweed ponds|
My husband place plastic pipes from one lake to the other. Then to keep the duckweed in and allow the water to flow out, he simply cut the bottom off a 2 liter soft drink bottle and insert this onto the plastic pipe. The excess water would escape and the duckweed would stay in the pond. Sometimes the solutions to problems are easier than we think.
We started these ponds with just a few duckweed plants and yet you can see how quickly and how full they became. It can double itself in about 16 hours!
You will need to help your duckweed to grow by adding manure. We used chicken manure which a friend of ours sells. He buys it in from a factory farm and it is extemely strong. My husband would half fill a plastic trash can with manure and add water to soften it. This he would then throw into the duckweed ponds with a bucket. This ensured it was spread throughout the pond. If you have put enough manure in, you will see a growth spurt. If you don't, look at the roots of the duckweed plant to see how long they are. If they are long, perhaps more than 2 inches, you need more manure. Duckweed loves mucky water. Infact there are countries, Palestine for example, which use duckweed to clean their water supply. It is one plant which has so many uses. For more information about some of the other uses, I have written another article on Hubpages.
Cleaning your duckweed pondI know what you are thinking, that this is going to be difficult but it isn't and it is necessary from time to time. If your duckweed seems to be slowing down with its reproduction it might be time to change the water and start again. We had to do this when we had a build up of sawdust in our ponds. This came in with the manure as this is what was used on the floor where the chickens were kept.
There are a couple of ways to do this, either let the water evaporate or drain it with a bilge pump, or a siphon. If you are going to be siphoning this, using your mouth to start the flow of water, remember how much manure you have been putting in there.
Remember keep some duckweed as a starterThis starter can be kept alive in water until your pond is ready to go again. Once dry, sweep and remove any twigs, leaves or other debris from your pond. This is a good time to inspect your liner below the water line.
Havesting your duckweedHarvesting is easy. We used a swimming pool net on an extendable aluminum pole. We briefly let the water drain from the net and then turned the duckweed into a large plastic box. We filled this full. This was then loaded onto our kayak to take to the tilapia which we had transfered to cages.
Because we were harvesting every other day we were able to check the liner for any problems above the water line as a matter of course. A quick once over as we were scooping it out meant any problems were dealt with early and were thus easier to control.
Cost vs SavingsThe cost for us was perhaps more than it would be for yourselves as we had to hire a machine to dig the holes for us. But compare this to the savings. If you calculate that your fish are only eating commercial fish food every other day, you have halved your food bill. If you only have a small number of fish, maybe this isn't commercially viable. We had bought 10,000 and had it definitely made financial sense to do this.
We produce healthy, weighty fish at half the cost of other fish farmers in this area.