Growing Aquatic Plants Part 12

The more I think about it, the more I like the idea of growing pond plants (aquatic weeds), both in order to clean up the nitrates etc in the ponds, and more importantly, as a free source of food for the tilapia!

You will probably remember (in part 8) that I have tried growing all sorts of plants and weeds, with a nil success rate. Since then, I have managed to start growing duckweed which the fish enjoy. I found out why. In the winter, it sinks to the bottom of the water in colder temperatures, remaining dormant until the warmer water stimulates growth. Then it comes back to the surface again and carries on spreading.

Phew, it wasn’t me then….

As an aside, duckweed can actually be eaten by us humans. In fact, it contains more protein than steak! It is also enjoyed by fish as well, and as it is so prolific (once you get it going) it is totally free fish food. That has got to be a good thing, as 5kg of the fish food that we buy costs £40 which they get through it in no time at all. Also, chickens love it so it will save on chicken feed, and it is even good for the dogs!

Furthermore, we use a lot of filtration and aeration equipment in the ponds to keep the water oxygenated. So by introducing lots of oxygenating plants and plants which extract the nitrates from the water we can give the fish a healthy environment to live in, and grow rapidly. Now all of this can be accomplished totally by nature using the aquatic plants and weeds. The challenge we will face is that apart from eating the duckweed, the herbivorous tilapia eat any other vegetation too. I tried a large water hyacinth plant and some small water lettuce in the tilapia pond the other day. Overnight, the fish ate every last bit!

So what we need to do now is to set up an aquatic plant nursery for a continuous supply of plants s fish food. Any surplus we get can go straight into the biogas system for supply free cooking gas.

(From my research I also found out that just like any other plant, aquatic plants need to be fed nutrients in order to grow quickly. I have never though of that – you would think they just needed water!  So I sourced some and apply a weekly does to the water.)

Time to put the thinking caps on…we needed a growing system that could be fed with fish waste, and where we could happily get the plants to multiply. I scoured the internet looking for various systems, and wasted a good few hours trawling through youtube videos, looking for the best method. Eventually I decided to come up with our own design. It consists of a main tank with the top cut off and filled with tilapia fish, then draining into 4 cut down IBC’s, and pumped back up into the main tank. Easy peasy…..

We tracked down some IBC containers from a company who agreed to deliver them, and I set about purchasing our initial stocks of pond plants and pond weeds from both the UK and here in Spain. Then I asked Javi to make up the system in his workshop whilst we were on a long weekend trip to the UK to see the family. I also had an idea of setting up another test aquaponic system along the outside wall of the greenhouse under the extension, using plastic drainpipes, with holes at certain intervals where we put the plants to grow in the water circulating through the pipes. Javi is going to be very busy!

We will report back soon, with how we got on.

Oh – I nearly forgot – the plants on our plantation are literally going berserk now. The moringa is knee high, the stevia are lush and green, the goji berry bushes are doing really well, and we haven’t lost a single avocado tree.

Take a look:

From left to right – Avocado tree, Stevia plants, Moringa plant, Goji berry plants

aguacate stevia moringa goji berry


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