Kevin Siedsma

Help! My seeds aren't germinating!

My time here at the aquaponics greenhouse has been a touch and go learning experience. Let me elaborate by going into detail about my trials and tribulations setting up the nursery. So all you, would be green thumbs, won’t repeat my mistakes.


Aquaponics - Mediamatic has their own urban agriculture system in the form of an Aquaponics greenhouse at the Biotoop Dijkspark, near Amsterdam Central station. Aquaponics is a way to sustainably produce food in the city, because it hardly takes up any space. Plants and fish are cultivated together. The fish excrete ammonia which gets transformed by bacteria into nitrate. The nitrate serves as fertilizer for the plants. Anisa Xhomaqi

I started by putting a bunch of seeds in little cups of soil like you would do in any old nursery. Well, this was a big mistake of course! Sure you could wash off the dirt before you put it in the substrate, because you sure as heck don’t want any soil in your system. The problem is that you would be messing up the delicate root systems of your seedling by washing it. This will end up in a stunted deformed plant. If you want to do it the right way, you have to put your seeds in rockwool pellets or something similar. Try to find them online or at the local garden center. Easy-peasy, no mess and once your seedlings are grown they can go straight into the expanded clay pebbles which we use for a substrate.

So if you have your seeds in little pellets, it is time for the next step; to get your set up going. Here in the aquaponics greenhouse we use a metal shelf with a strip of LED lights at the bottom of each shelf with the right light frequency for green plant growth. Now be sure everything is well insulated, because you want to  catch as much heat as possible. I use styrofoam on the top of the shelves and reflective insulation material for the surface.

Finally, I  finished my setup. The nursery was well insulated, I had my LED lights set up and some thermostats to keep an eye on the temperature. So everything was watered warm and well lit and yet there was still something not quite right. The amount of seeds that germinated was disappointing and what did germinated was discolored. Where did I go wrong?

Well turns out plants need a day and night cycle just about as much as you and me. The problem was easily solved by putting a timer on the power outlet. Giving the plants a nice six hours a day of nap time. 


Nursery Shelf - Kevin Siedsma


So to reiterate the necessary steps for your nursery are:

-Make it warm and insulated, but not too insulated, you still want a little airflow or otherwise things could get mouldy.

-Enough lighting, but be sure to have a day and night cycle.

-Use rockwool pellets or something like vermiculite if you are working with a substrate.

-Enough water. Don’t let the pellets dry out.


Sprouting Plant - Kevin Siedsma