Hydroponic seed starting is simpler than it seems. Hydroponic seed starter kits consist of seedling trays, humidity domes, LED lights, and a heating mat. Seed starter kits are vital to starting your hydroponic seeds. While it is possible to just start seeds using a paper towel, your germination rate is much higher while using a seed starter kit.

Keep reading to learn all about starting seeds hydroponically!

What Exactly Is A Seed Starter Kit?

Seed starter kits make hydroponic seed starting easy. They consist of seedling trays and humidity domes. Other things that may be involved in a seed starter kit include LED seedling lights and a heat mat.

The goal of a seed starter kit is to be able to germinate seeds with nothing but the kit.

Are These Truly Worth The Investment?

Isn’t it possible to just use a paper towel to start your seeds? Or simply plant your seeds directly into your growing medium?

You can definitely use these methods, but your germination rate will be way lower than if you use a seed starter kit. You’ll also have to wait longer for your seeds to germinate.

The two main benefits of germination kits is that they improve the success rate and efficiency of seed sprouting.

What equipment do you need to start seeds for hydroponics?

You need a grow tray, humidity domes, a humidity kit, LED lights, and a heat mat for hydroponic seed starting. You will also need germination plugs or another kind of medium.

Starting medium

There are lots of different kinds of starting mediums that you can choose from. Let’s go over some of them! 

Coco coir

Woman using garden tools

Coco coir is great at retaining water, so under- or over- watering isn’t too much of a concern. It’s incredibly sustainable and you can even find organic options. It’s porous and lightweight, as well as anti-fungal. This means you don’t need to use as many chemicals.

Coco coir is one of the best choices for beginner growers and expert growers alike!

Rockwool Cubes

Rockwool cubes are great for enclosed starters that have more airflow around their roots.

Rockwool cubes have holes already drilled in them and have plenty of space for roots to grow before you transplant the hydroponic seedlings into a larger container. 

Rockwool cubes also have wonderful drainage, so root rot is very unlikely.

Starter Plugs

Hydroponic starter plugs don’t offer as much room as rockwool cubes but are still great to use. Starting cubes are sterile and you don’t have to soak them in water before you use them. Find starter plugs that are roughly pH-neutral.


Netcups are another popular option for hydroponic seed starting. Netcups come sterile and you don’t have to soak them before starting. They have a label that makes it easy to know how deep to plant your seeds, which is helpful if you’re just starting out.

Humidity Dome

Humidity domes are essential for hydroponic seed starting. Put the humidifier on a level surface at least a foot away from the tray with good airflow.

Search for a dome that has at least two vents per side if you want the best results. This helps your seeds and plants get enough airflow.

Domes also need adequate space between them so that they’re not touching or overlapping or else the hydroponic seedlings can run into trouble from not having enough airflow.

Heating Mat

Heating mats create moisture and warmth throughout the hydroponic seed germination process, which really helps the seeds out. Heating mats also help battle the cold air conditioning in your home to keep your plants warm.

Grow Lights

While you can technically use natural light, artificial lights are a must if you want to create the best conditions for your seeds to sprout. There are a couple different kinds of grow lights available.

HID Grow Lights have a large spectrum range. HID grow lights are great for plants that you’re growing in the vegetative stage because it has a huge spectrum range compared to other hardware.

LED lighting that has a lower heat output is better for plants that flower.

Flourescent lights are inexpensive but aren’t as effective as LED or HID lights because they don’t emit much blue light.

CFLs are cheap and emit plenty of green and red light. 

Nutrient Solution

Unless you’re an advanced grower, you’ll likely want to buy a preformulated nutrient solution. It’ll come with instructions for how to mix and use it.

In order to monitor your nutrient concentrations, you need to measure the EC (electroconductivity) of your solution. Use an EC meter to detect the amount of total dissolved nutrients in the solution. The package will tell you what EC range you’re looking for. 

Just be wary that EC isn’t a great indicator if you’re using an organic nutrient solution.

Record your EC when you mix your solution and then keep track of it daily. As your plants take up nutrients, you EC will drop. When the EC drops below the desired range, that’s an indication that it’s time to add more nutrients. You’ll know how much more to add based off of the percentage drop you recorded in the EC.

You can also take measurements from the nutrient solution and from sample areas in your growing medium. This will help you catch if your medium is developing a nutrient build-up.

Germinating Seeds

germinated seed sprouts have grown and need to be planted in the soil

Here’s how to germinate seeds! For the sake of simplicity, we’re going to talk about germinating seeds using cubes.

1. Get the seed starting medium ready.

Make sure you have a big enough container. Be sure that there’s adequate room for aeration between roots (so they’re not too deep in the water). 

Filter tap water or use pure water while starting your seeds. 

Always test your pH to make sure it’s in range. You can use a low-dose nutrient solution at this point because you don’t want to overload young seedlings with too many nutrients.

Fill your container with water and nutrient solution and then place in your starter cubes to absorb some of your solution.

2. Planting your seeds.

Some cubes come with holes for you to plant your seeds in, while others don’t. Don’t plant your seeds more than 1/4 inch below the surface.

Take a few seeds and gently put the into the hole. Cover them slightly with rock wool or something similar.

Now cover your container to create a dark environment. Keep a temperature of at least 68 degrees F. Use a heating mat if temperatures are lower than that. 

3. Check your water levels.

It’s a good idea to check your water levels every day and keep your cubes moist. 

If more than one seed germinated in a single hole, don’t pull any of them out because it may damage the roots of the one you leave in.

Once the first true leaves show, cut off the smaller shoot as close to the cube as possible.

4. Sun and light exposure.

A good light source is vital for hydroponic seedlings. If you’re using sunlight, three hours a day should suffice. You want to aim for closer to five hours a day if you’re using artificial lighting. When your plants get bigger, they’ll need as much as 15 hours a day!

Transplanting The Seedlings

Seedlings are usually ready to be transplanted to your hydroponic system in 2-3 weeks. Once the root growth shoots through the bottom of the rock wool, that’s a sign that they’re ready.

Your baby plants are very vulnerable during transplant. They may go into shock, but if you take good care of them they’ll turn into thriving, healthy plants.


Clearly, seed starter kits are the best way to start hydroponic seeds. They increase the germination rate of your plant seeds and make things easy for you. Now that you know how to start your hydroponic seeds, read more of our blogs to learn about growing your own fruits and vegetables!