How to Culture Microworms at Home (Without the Smell Taking Over Your Fish Room)

October 28, 2025

If you’ve ever opened a microworm culture and thought, “That’s a smell I’ll never forget,” you’re in good company. These little nematodes are incredible for growing fry — but yes, they do come with a certain… aroma.

The good news is, with a few smart tweaks, you can keep your cultures thriving without turning your fish room into a biology lab gone wrong.

In this guide, I’ll walk you through exactly how I culture microworms at home — step by step.

It’s easy, it’s cheap, and if you do it right, you’ll have a steady supply of live food for your fry for months on end. We’ll also tackle the big question: how do you keep them productive and odour-free?

If you’re new to these wriggly wonders, you might want to start with What Are Microworms? The Perfect Next Step in Feeding Growing Fish Fry — it explains what they are, why they’re ideal for slightly larger fry, and how they fit into your feeding routine.

But for now, let’s get our hands (slightly) dirty.

What You’ll Need

Setting up a microworm culture doesn’t require anything fancy. Most of what you need is probably already in your kitchen.

Porridge oats — plain, unsweetened, the kind you’d use for breakfast.
Yeast — standard baking yeast works perfectly; it’s what keeps the worms fed.
Microworm starter culture — you can grab one here to get going.
Plastic container with lid — any small food tub or takeaway box will do.
A spoon or spatula — for mixing and spreading the medium.
Spray bottle of dechlorinated water — optional, for keeping things moist.

I tend to keep my cultures in small, stackable tubs. The kind you might get from your local takeaway work well.

They take up almost no space, and if one ever goes bad, it’s easy to replace. Trust me — having a few backups running at once is worth it when you’re feeding fry daily.

Setting Up Your First Microworm Culture

Here’s the step-by-step method I’ve used for years. It’s simple, reliable, and keeps the smell to a minimum.

Prepare the base. Place a few tablespoons of porridge oats into your container. Add a small splash of water — just enough to make a soft paste. You don’t want it runny; think “slightly soggy porridge.”
Add yeast. Sprinkle a light dusting of yeast across the surface. This will kickstart the fermentation that microworms love to feed on.
Introduce the starter culture. Take a small scoop from your live microworm starter and spread it thinly over the top. It doesn’t take much — a teaspoon’s worth is plenty.
Cover loosely. Place the lid on, but don’t seal it airtight. Microworms need a bit of oxygen, and trapped moisture can lead to mould. I usually poke a few small holes in the lid or leave one corner slightly lifted.
Find a warm spot. Keep the container at room temperature — around 22–26°C is perfect. Too cold, and they’ll slow down; too hot, and the culture might crash early.

In about two to three days, you’ll notice a shimmering layer of tiny, moving threads climbing up the container walls. That’s your cue — you’re officially a microworm farmer.

Harvesting Microworms Without the Mess

Harvesting is where many people go wrong. You don’t want to scoop the whole messy medium into your tank — just the worms themselves.

The easiest way is to use the “wall scrape” method:

Look for the cloudy, moving film of worms crawling up the sides of your container.
Use a cotton bud, clean finger, or small spatula to wipe a little off.
Swirl that in a small cup of aquarium water to rinse away any residue.
Use a pipette or syringe to add the worms to your fry tank.

That’s it — no smell, no gunk, no cloudy water. You can repeat this multiple times a day without disturbing the main culture.

Each culture will usually last around three to four weeks before productivity drops. When that happens, it’s time to start fresh (more on that below).

How to Restart a Culture When It Ages Out

Even the best cultures slow down eventually. The oats break down, the yeast runs out, and the worms stop reproducing as quickly. That’s when you “seed” a new batch.

Set up a fresh container with oats and yeast, exactly as before.
Take a small scoop of active worms from the walls of your old culture.
Spread that onto the surface of the new mix.
Cover loosely and keep it warm.

I like to start a new culture every two weeks. That way, I always have one at its peak while another is just starting to build. It’s a simple rotation system that ensures you never run out of live food — even if one batch suddenly crashes.

Old cultures can go into the compost bin (they’re full of organic material) or the bin if you prefer. Just don’t pour them down the sink — the mix can stick and smell for days!

Avoiding Odours and Mould (Honest Practical Tips)

Let’s be real: microworm cultures don’t smell great at the best of times. But there’s a big difference between a faint, yeasty aroma and an overpowering stink that makes your partner question your life choices.

Here’s what I’ve learned from trial and (a fair amount of) error:

Don’t overwater. Too much moisture is the number one cause of foul smells and mould. Keep the medium moist, not wet.
Use smaller batches. A fresh culture every two weeks smells far less than one left festering for six.
Keep lids loosely fitted. Airtight containers trap odours and promote anaerobic bacteria — the real stink culprits.
Store in a ventilated area. A small shelf near your fry tanks works well. Avoid enclosed cupboards.
Feed sparingly. You only need a light dusting of yeast to keep things ticking. Too much yeast = faster rot.

Some breeders even add a pinch of cinnamon powder to their culture to reduce odour and slow mould growth. I’ve tried it, and while it doesn’t turn your fish room into a bakery, it does help a little!

My Routine for Clean, Low-Smell Cultures

After years of trial and error, I’ve settled on a simple weekly rhythm that keeps everything under control:

Day 1: Start a new culture with oats, yeast, and a fresh starter.
Day 3: Begin harvesting small amounts.
Day 7: Harvest daily and check moisture levels.
Day 14: Start a second culture — this becomes your backup.
Day 21–28: Retire the first culture once productivity drops or smell increases.

This rotation keeps my fish fed, my shelves tidy, and the air breathable. Once you get into the habit, maintaining live food cultures becomes just another easy part of your fishkeeping routine — like topping up water or trimming plants.

Final Thoughts

Culturing microworms might sound a bit “mad scientist” at first, but it’s genuinely one of the easiest and most rewarding DIY projects in fishkeeping.

The payoff is huge — healthier fry, faster growth, and the satisfaction of being completely self-sufficient with live food.

If you’re still feeding your fry only vinegar eels or powdered food, give microworms a try. They’re the perfect next step up — easy to maintain, rich in nutrition, and adored by fish fry everywhere.

You can start your first batch with a Microworm Live Food Culture from our shop — everything you need to get going is included.

And if you’re curious how they stack up against vinegar eels, check out our upcoming post: “Vinegar Eels vs Microworms: Which Is Better for Fry?” It’s a fascinating comparison for anyone serious about breeding success.

With a little care (and a peg for your nose), you’ll soon wonder how you ever managed without these tiny, wiggly lifesavers.

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