And what you can do about it.

If your worm-based wastewater system isn’t working like it used to, or you’ve peeked inside and thought, “Where did all the worms go?”- you’re not alone. Worm-based septic systems are incredible at quietly managing waste, but like any living ecosystem, they need the right conditions to thrive. This blog unpacks what might be going on when worms start disappearing or dying, how these systems work, and simple tips to keep them in good shape.

Septic tanks vs worm systems: what’s the difference

First, not all wastewater systems are built the same. Traditional septic tanks are passive systems that rely mostly on gravity and anaerobic bacteria (bacteria that work without oxygen) to break down solids over time. They’re fairly hands-off but slow and not always environmentally ideal.

Worm-based wastewater systems (or vermifiltration systems) are more dynamic. They use aerobic bacteria (which need oxygen), filtration layers, and most importantly, compost worms to break down waste much faster and more efficiently. In short, septic tanks are like slow compost piles. Worm systems are more like finely tuned ecosystems. But they need a bit more care.

Learn about the power of vermiculture here. 

When worms stop working: what might be going wrong

If worms seem to be disappearing or dying, the good news is it’s often fixable. Most of the time, it's not about failure - it's about balance. Here are the most common reasons the system might not be working properly.

Too much fat, oil and grease

Worms breathe through their skin, which means they need a clean, moist, oxygen-rich environment. When too much fat, oil or grease goes down the sink, it can coat the bedding material and block airflow. Without oxygen, the worms can suffocate.

What to do:

• Avoid pouring cooking fats or greasy water down the drain.
• Scrape plates before washing and let pans cool so you can wipe them out before rinsing.

Harsh chemicals and detergents

Certain cleaning products, like bleach, antibacterial soaps, or strong dishwashing powders - can upset the microbial balance that worms depend on. In some cases, these chemicals can be toxic to the worms themselves.

What to do:

• Choose septic-safe, eco-friendly cleaners.
• Avoid pouring concentrated products directly into sinks or drains.
• Dilution is key - most cleaners are fine in small amounts, especially when rinsed well.

Not enough food (yes, it happens)

Worms in wastewater systems get their food from the organic matter in greywater - things like tiny food scraps, soap residue, and organic solids. If a system goes unused for long periods (like in a holiday home) or only receives clean laundry water, the worms might not be getting enough nutrition.

What to do:

If your system is underused, consider occasionally adding a small handful of compost or organic food scraps. Your installer or provider can advise what’s safe.

Are the worms dead or just hiding?

Sometimes worms retreat deeper into the bedding when surface conditions are off - too wet, too dry, too hot, or lacking oxygen. Before assuming the population is gone, gently check below the surface. If you find moist bedding and a few active worms, the system may just need some adjustment rather than a full reset.

Bonus tips: what else should you know about worm-based wastewater systems?

Keep water flow steady, not sudden. Large surges (like back-to-back laundry loads or long showers) can overload the system. If possible, space out water use to give the system time to process it properly.

Check the bedding layer. Most systems have woodchips, compost, or coir at the top. If it’s slimy, compacted, or smells bad, it might need refreshing.

Avoid non-organic waste. Don’t send down anything you wouldn’t compost: no paint, coffee grounds, meat scraps, or solvents.

Worms love consistency. Systems exposed to weather can be affected by extreme cold or heat. Shade, insulation or simple covers can help maintain more stable conditions.

Don’t keep adding worms. If worms are dying, adding more won’t help unless the environment is corrected. A healthy worm system is self-sustaining.

Keep it wriggling: small tweaks, big results

Worm-based wastewater systems are an excellent low-impact, high-efficiency alternative to traditional septic tanks, but they’re alive, and that means they need the right balance to keep working well. If your worms seem to be disappearing, chances are it’s something simple that can be fixed with a few tweaks to your habits. Think of it less like fixing a machine, and more like helping a garden get back to health. 

If in doubt, give us a call and we'll come and give your tank a check-up. A little maintenance now can prevent major issues later.