Plants Stuff

Starting Seeds For Aquaponics

Have you ever wondered how seeds are started for planting into an aquaponic system? Well, today’s episode is all about the options and methods available to get little plants going in your aquaponic system.

You’re listening to Fish Grow Plants—A podcast all about practicing and sharing the love of aquaponics; hosted by Logan Schoolcraft.

Hello, and welcome to Fish Grow Plants! In today’s episode we’re talking about starting seeds for aquaponics.

So, did you know that for the longest time I struggled with this? It’s true. I remember way back, even as a kid not understanding why some of the seeds I would plant would come up and why some would not. I have this oddly strong memory of a vague mounded hill for squash where I planted what seemed like a lot of seeds, yet nothing came up. And, not 50 feet from there, I remember literally dumping 5 year old flower seeds out on top of the ground thinking “whatever-if they come up, fine; if not fine.” And you know what, those flower seeds took off! The squash never did—I think we dug up the hill and found the seeds just as they were, only a little softer.

Even with the random types of gardens my parents had over the years, and the few planting projects that came up here and there, I still seemed miffed at seeding.

It wasn’t until a few years ago the phrase, “it’s a numbers game” was used in relation to starting seeds and that’s when the lightbulb went off!

I know this might not resonate with everyone, but for me, it was golden. It really did explain a lot of why I struggled with the whole seed concept. (No, it doesn’t explain everything, but it worked wonders for me.)

Here’s my interpretation:

Seeds are finicky, just like people. So, you can’t count on them 100% of the time. That’s why they have a number called a germination rate, or ratio. That means how many seeds out of 100 will probably come up in a given sample seeding. So, an 85% germination rate means 85 of 100 seeds will actually germinate.

So, taking that into consideration, you have to know that not every one of your seeds will make a plant where you drop it. And, even if the seed does germinate, it’s got a lot of work, competition, and struggles to make it through its early life. There’s no number for this, but it’s worth assuming it’s not 100%.

As an aside, I know you can have 100% germination. I’ve even done it, but just because it can be done, doesn’t mean you should count on it. Invariably, when you need the 100%, it will not happen.

So, when I realized that planting one seed does not mean one plant, bells, lights, and whistles went off in my head—I realized it’s essentially a compounding math problem.

The way to work this problem the best? Work backwards. Really.

Here’s a quick example. Say you want 100 plants fully grown in a few months. If you have seeds that have a 90% germination rate, you need to plant at least 112 seeds. But, what about that other un-named rate for when the seed is young? Well, it kind of comes from experience and how well you think your process is. If your confident, you could assume 90 or 95%. If you’re new, maybe 50 to 75%. So, if your confident in your processes, you’d still have to allow for a few extra seeds, which would mean your total seeds to plant are now at 124. This process is iterative. If you have any other processes that cull, transfer, pluck, or could in any way mean getting rid of a plant, you can “roughly” account for that before even beginning your planting!

But you want to know a kicker to this math problem?

Everything you choose adds a bit of a variable that can alter or impact your results. We’re not going to dive into the math of this, even if it sounds awesome right now.

Rather, we’re going to take a look at the variables themselves. Uhm, what I should have said is that we are going to talk about the products, options, and combinations available to the aquaponic practitioner for starting seeds.

Let’s take a look at the media first.

When it comes to seed starting options, your media selection is actually pretty wide. But if you condense it down, you have four basic options:

  1. Organic material
  2. Inorganic material
  3. Synthetic material
  4. Combination of materials

Each has its strengths and weaknesses, but from my experience, it comes down to adult diapers again—it depends on what you have access to, what you can afford, and if you like working with it.

Alright, for organic material, you have the options of:

  1. Peat
  2. Coco fiber
  3. Wood-based products

For the inorganic material options, you have:

  1. Sand
  2. Pumice
  3. Volcanic rock
  4. Vermiculite
  5. Perlite
  6. Expanded clay
  7. Stone wool
  8. Zeolites

And for the synthetic materials, you can choose from:

  1. Expanded polystyrene, and
  2. Polyurethane foam

OK, I know that list is not complete, but it should be a great place to start.

But what about the material combinations, you ask?

Well, they are just that, combinations of materials. For example, I mostly use an organic coco fiber mixed with vermiculite for good water retention, ease of use and cost. I’ve also used variations of gravel, clay, and foam; all with less than satisfactory results. That doesn’t mean it’s any worse or better. It just means that my situation back then did not pair well with that media.

Alright. Once you have your media selected, you need to choose what you are going to put your media into. In other words, are you going to start your seeds directly in net pots, seeding trays, or another container.

When choosing your seeding container make sure it’s sized for the seeds you’ll be starting as well as acceptable for your media. For example, you wouldn’t want to use sand with net pots, or expanded polystyrene with tiny seeds started directly in your system—they are going to have issues.

I’ll be the first to say that sometimes doing experiments and seeing what works for you is good; after all, you might figure out a really great method. But, for most of us, starting with a known method or product is a solid bet that your results will be positive.

Not to wear the adult diapers out here again, but the product and method you choose to use depends on your situation. What I mean is when, where, and how you start your seeds. I’ve had good luck using most methods, but they apply to certain plants. For example, I have excellent results with starting Moringa directly in my aquaponic system, but most leafy greens I’ve tried don’t like that. They prefer to be started outside the system.

Since I’m new to indoor growing, I’m learning a whole lot more as well. Apparently, things that work outside, or in a greenhouse don’t always work indoors under grow lights.

I realize this may all be a long-winded way to say I cannot recommend one type or way of combining your seeds and seed “hardware” since the variability is wide.

That being said, I can tell you some of the common methods and products out there, both that I have tried, and a few I have not, but that are still readily available and priced fairly.


When I use an approximate 50/50 coco coir and vermiculite mix to start my seeds, I’m either putting them in a 98 cell flat, or into 2” net pots. I really like using Cz garden net pots because of their wide lip and sturdy construction. I also really appreciate the net pot holder by Bootstrap Farmer, as well as their 1020 trays to hold the net pots or the 98 cell trays. At this time, I have no preference to the 98 cell tray sourcing.

I have several types of clear domes and they all seem to work fine, but the taller the dome, the more growth you get inside it. I notice my flower starts jump up pretty tall early on and a tall dome is handy for them.

A few things I have not tried but hear about, read about, and can find online for starting seeds are coco and/or cotton plugs, rockwool and other inert plugs that can go from starting tray to system with ease.

Usually, the 1020 trays, cell flats, covers, and related hardware are quite similar between sources, so it usually comes down to getting a good deal, or the closest option, for me.

For the last adult diapers of this episode, I’d say don’t sweat getting it right the first time. Do sweat finding a method you feel comfortable with and have the ability to follow through on. If you can do that, with only a few iterations, you’ll be just as proficient as anyone planting seeds for aquaponics. And if you do a few hundred or thousand every week or so, you’ll probably be able to tell me what really does work best for you.

So good luck getting your seeds going, and as always, happy aquaponicing!


Questions! Let me have them! Do you need clarification, more information, or maybe you just have a tangent thought—send all your thoughts my way. See the website for episode details, or just fire off an email to [email protected] and I’ll get back to you.


So, was this episode good, bad, ugly, or other? Let me know! Comment, email, smoke-signals it doesn’t matter! I love to hear from you. Your feedback is immense, and I am always grateful for it. Likewise, thank you for taking the time to listen and share your thoughts. Have a wonderful day.

This has been another episode of Fish Grow Plants—the podcast all about practicing and sharing the love of aquaponics; hosted by Logan Schoolcraft.