Germinating Seeds in Hydroponics or Aquaponics
Author: Aqua Gardening
Date: 9 December 2021

Germinating Seeds in Hydroponics or Aquaponics

Place your seeds in the fridge

Place your seeds in the fridge or freezer for 12 - 24 hours before germinating them. This creates an artificial winter and when they are planted in a warmer place it signals them to germinate.

Balance the ph of your water

Balance the pH of your water to 5.5. You can use pH down solution and a pH pen to get the right pH. If you have some rooting tonic add 1-2ml per 1L of water. We recommend Bloom Roots, Rhizotonic, or Roots Excelurator. Rooting tonic speeds up the plants growth and promotes thicker roots once the seed germinates.

Prepare your grow cubes

Soak your rockwool cubes or peat pellets in the water that you prepared in the previous step. Rockwool is best for hydroponic and aquaponic systems whereas peat pellets are better for coco and soil systems. Leave them to soak for a minute and make sure the water is dispersed throughout. After a minute, pick your grow cubes up and give them a very slight squeeze so that they are damp but not water logged. The remaining solution can be used for watering later.

Plant your seeds into grow cubes

Plant your seed at a depth of the width of the seed into the grow cube (if the seed is 2mm wide, plant the seed 2mm below the surface of the grow cube.) Make sure that the seed maintains contact with the grow cube.

Place your grow cubes into a propagator

Place your grow cubes on a lattice tray inside your propagator. Ensure the excess water can drain from the grow cube so that it is not sitting in water. Put the lid on the propagator unit and place it in a dark place for the seeds to germinate.

Use a heat mat

Use a heat mat under the propagator to keep the grow cubes at around 25°C. The warmth of a heat mat helps seeds to germinate faster.

Keep your grow cubes moist

Check the grow cubes after a couple of days. They should still be moist, if not spray or drop some of the root solution onto the cube. The grow cubes should be kept moist but not water logged. If there is too much water there is not enough oxygen for the roots to grow and the seed and the roots will rot.

Add some lighting

Once your seeds have germinated and the first leaves have appeared, you can give then some light. The right amount of lighting is critical once your seeds have germinated. Not enough sunlight will cause your seedlings to become leggy. Direct sunlight will cause seedlings to dry out very quickly. We recommend the PS1 Purple lights or other CFL grow lights for the best results when germinating seedlings. You can leave your seedlings under the lights for 18-24hrs a day.

Add some nutrient solution

Once roots start emerging from your grow cubes, you can add a solution of nutrient no higher than EC=1.0 to the propagation tray. If you don't have an EC meter, you can use watered down nutrients at a 1/4 of the recommended strength.

Plant your seedlings

Once there are 2-3 nodes on your seedlings or roots have emerged from the base of your grow cubes, you can plant the seedlings into your grow media.

Common problems when germinating seeds

Here's a list of the most common errors when germinating seeds:

  • Keeping rockwool cube too wet and causing the seed to rot. Use a lattice tray or a tray with plenty of drainage
  • Not providing enough warmth
  • Too much light before the seed has sprouted
  • Letting the air go stagnant (ie: not allowing fresh CO2-rich air into the propagation box.)