Why Heat Packs Are Essential for Fish Transit in Winter

At Chloe's Aquatic Centre, we take the health and safety of every fish we ship seriously — especially during the colder months. One of the most important tools we use to ensure your fish arrive alive and stress-free is the humble heat pack. Here's everything you need to know about why we use them and how they work.

What Is a Heat Pack?

A heat pack (also known as a hand warmer or livestock heat pack) is a self-activating chemical pouch that generates a steady, controlled heat when exposed to air. Designed specifically for live animal transit, aquatic heat packs typically maintain temperatures between 30–40°C for 40 to 72 hours, depending on the product used.

They are placed inside the insulated shipping box alongside the sealed fish bag, providing a warm microclimate that protects your fish from the cold ambient temperatures outside.

Why Temperature Matters for Fish

Fish are ectothermic (cold-blooded) animals, meaning they cannot regulate their own body temperature — they rely entirely on their environment to stay warm. Most tropical fish species kept in home aquariums thrive at temperatures between 24–28°C. When water temperatures drop below this range, even briefly, the consequences can be severe:

• Immune suppression: Cold stress weakens a fish's immune system, making them highly susceptible to bacterial and fungal infections such as ich, fin rot, and columnaris.
• Metabolic shutdown: At low temperatures, a fish's metabolism slows dramatically. They become lethargic, stop eating, and in extreme cases, enter a state of cold shock.
• Osmotic stress: Cold water affects a fish's ability to regulate salt and water balance across their gills and skin, leading to osmotic stress.
• Death: Prolonged exposure to temperatures below 18°C can be fatal for most tropical species within hours.

The Risks of Winter Shipping Without Heat Packs

During Australian winters, overnight temperatures in many regions can drop to single digits — particularly in Victoria, South Australia, Tasmania, and elevated inland areas. Even with express shipping, a fish bag sitting in a cold courier depot or delivery van overnight can lose heat rapidly.

Without a heat pack, a bag of tropical fish can drop to dangerous temperatures within just a few hours. By the time your parcel arrives, the fish may be in cold shock, severely stressed, or deceased — even if the transit time was short.

How We Use Heat Packs at Chloe's Aquatic Centre

We carefully assess weather conditions at both our end and your delivery location before every shipment. During winter months (typically May through August, and sometimes into September depending on conditions), we include heat packs as standard with all live fish orders.

Our packing process includes:

• Double-bagging fish with an oxygen-rich atmosphere
• Wrapping bags in insulating material to retain heat
• Activating and placing the heat pack in a position that radiates warmth without direct contact with the fish bag (to avoid overheating)
• Sealing everything in a polystyrene-lined box for maximum insulation

What You Should Do When Your Fish Arrive

Even with heat packs, it's important to handle your new arrivals correctly to minimise further stress:

• Open the box promptly upon delivery — don't leave it sitting in the sun or in a cold area.
• Float the bag in your aquarium for 15–20 minutes to slowly equalise the temperature.
• Do not drip acclimate if the bag water is significantly colder than your tank — a slow temperature rise is safer.
• Check the fish for signs of cold stress (lethargy, clamped fins, pale colouration) and monitor closely for the first 48 hours.

Our Commitment to Live Arrival

We are passionate about the wellbeing of every animal we ship. Our live arrival guarantee, combined with careful packing and the use of heat packs during cold weather, reflects our commitment to getting your fish to you in the best possible condition. If you ever have concerns about weather conditions at the time of your order, don't hesitate to reach out — we're always happy to discuss the best shipping options for your location.

Stay warm out there — and so will your fish. 🐟