Steady 78°F Tropical Warmth. Zero Clutter.
Ditch oversized 120V pet-store tubes and failing suction cups.
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Every component of the Cosari MicroTherm 10W (Model QL-222) is built to protect delicate aquatic life without ruining the clean lines of your desktop tank.
Visible through the thick clear glass lower tube, densely packed dark quartz granules absorb and radiate gentle 10W warmth evenly into the water column within an hour.
Set into the glossy black upper housing, the front square display window lets you confirm active thermal regulation at a glance without guessing if your heater is working.
Replaces intimidating 120V AC mains current with safe low-voltage 5V DC power via an integrated black USB-A cord that routes neatly over rimless glass edges.
The deep-grooved matte black bottom cap cushions the glass cylinder against hardscape rocks and substrate while protecting curious bettas and dwarf shrimp.
Once fully submerged, the upper head continuously monitors water temperature and shows active status through the front square window—eliminating the sudden thermal spikes of cheap mechanical switches.
Instead of an exposed glowing wire that creates scorching hot spots, the 10W element warms a dense bed of dark quartz granules inside thick clear glass, bringing a 2.5-gallon tank up to temp within 60 minutes.
Anchored by its mineral core and ribbed matte black bottom cap, the compact cylinder sits steadily on dark gravel or behind plants without clunky rubber suction cups that detach and float.
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5V/2A Low-Voltage USB Submersible Quartz-Sand Nano Heater for 1–3 Gallon Betta, Shrimp & Desktop Tanks
Backed by our 30-Day Money-Back Trial & Full Cosari Guarantee.
$49.99 $99.99 Free Tracked Shipping (5–7 Days) Included
In Stock: Delivers in 5–7 Business Days. Free insured US delivery with tracking.
30-Day Money-Back Guarantee plus a full 2-Year Warranty.
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Why Nano Tanks Need Dedicated 10W USB Heating: Standard 25W to 50W aquarium heaters were designed for 10-to-20 gallon tanks and rely on 120V bi-metallic contacts that can overheat a 2.5-gallon bowl in hours. The Cosari MicroTherm 10W (Model QL-222) uses low-voltage 5V/2A USB power and a dark quartz-sand thermal mass to deliver gradual, steady warmth tailored specifically for 1-to-3 gallon water columns.
Architectural Materials & Build: Crafted with a glossy black upper housing featuring a clear square front window, a thick transparent glass lower chamber filled with dark thermal quartz granules, and a protective ribbed matte black bottom cap. The permanently sealed black power cable terminates in a standard USB-A connector for effortless routing behind desktop tanks.
Shipping & 30-Day Guarantee: All orders ship with Free Tracked Delivery directly from our warehouse. Every Cosari MicroTherm 10W is protected by our 30-Day Money-Back Guarantee so you can verify its accuracy in your own tank risk-free.
Free 5–7 Day US Shipping: Every order ships free with full tracking and delivers in 5 to 7 business days.
30-Day Trial: Try it at home for 30 days risk-free. Need help? Email us anytime at support@buycosari.com.
2-Year Warranty: If anything goes wrong within 2 years, we replace it free of charge or refund your order in full.
Prevents rapid temperature swings and dry-burn cracking by buffering heat inside high-density dark mineral granules.
Takes up a fraction of the space of traditional glass tubes—so your betta actually enjoys swimming around it rather than losing half its bowl.
Precision-molded matte black bottom ribs prevent glass-on-rock contact against seiryu stone, dragon stone, or bare-bottom hospital tanks.
Cosari MicroTherm 10WStandard Competitors
| Feature | Cosari MicroTherm 10W | Standard Competitors |
|---|---|---|
| Power & Electrical Safety | Safe 5V/2A Low-Voltage USB-A | 120V AC Household Mains Current |
| Status Visibility | Clear Square Front Display Window | Blind Black Plastic Paddle (No Window) |
| In-Tank Placement | Weighted Quartz Core (No Ugly Clips) | Slimy Suction Cups That Pop Off |
| Nano Tank Footprint | Thumb-Sized Cylinder for 1–3 Gal | Bulky 7–9 Inch Industrial Tube |
| Bedroom & Desk Noise | 0 dB Solid-State Silent | Audible Bi-Metallic Relay Clicks |
Swipe left for steps 2 and 3
Place the weighted cylinder vertically or horizontally near the bottom substrate of your 1–3 gallon tank and wait 5 minutes for the internal sensor to acclimate to water temperature.
Route the thin black cord neatly over the tank rim (forming a small drip loop) and plug the rectangular USB-A connector into any standard 5V/2A USB wall adapter.
Confirm active status through the front square window and watch your betta or shrimp enjoy steady, silent tropical warmth within the hour.
This keeps my 2.5-gallon tank about 7 degrees warmer than the room. My betta likes swimming around the heater, and it doesn't take up much room in his tank.
My desktop nano tank reached temperature within an hour. The heater feels sturdy, looks nice, and runs completely silently. I also like that the whole unit is submersible.
I've had this in my small desktop quarantine tank for two weeks with no issues. The temperature matched my separate tank thermometer, and the square front window makes the heating indicator easy to see.
This arrived quickly and saved his poor fishies from Davy Jones locker! It was fully assembled, so we plugged the USB-A cord right in out of the box and it worked perfectly.
Works perfectly for my bettas. The little black-and-glass cylinder fits neatly in a small betta setup without getting in the way.
I like not having to fuss with the settings. It automatically keeps my small tank around 78°F, and the display is easy to check when I walk by. My fish seem comfortable.
I use this in my 2-gallon desktop tank. It was less expensive than the heaters I saw at the pet stores and has kept the temperature steady so far. No issues yet.
Great little heater for my desktop shrimp bowl. It fits without crowding everything and keeps the water warm. Works good! Would buy again.
My office gets pretty cold, but this USB heater keeps my little desktop tank steadily warmer. It's compact enough that my betta still has plenty of room to swim.
I checked the water with a separate thermometer and the temperature was right where I expected it. The front indicator window is clear, and I like the look of the dark sand in the lower tube.
$49.99 $99.99 Free Tracked Shipping (5–7 Days) Included
In Stock – Free 5–7 Day US Shipping · 30-Day Risk-Free Trial.
The Cosari MicroTherm 10W (Model QL-222) is precision-engineered for 1-to-3 gallon nano aquariums, desktop betta bowls, dwarf shrimp tanks, and quarantine hospital setups, holding water temperatures roughly 7°F above ambient room temperature up to the tropical sweet spot.
It features an integrated flexible black power cord terminating in a standard rectangular USB-A plug. Simply connect it to any standard 5V/2A USB wall adapter or powered desktop USB hub for safe low-voltage operation.
By design, it does not use bulky rubber suction cups that turn slimy and detach. Thanks to its dense dark quartz-sand glass lower tube and ribbed matte black bottom cap, it is naturally weighted to sit vertically or horizontally right on top of your substrate or tucked behind rocks and plants.
The glossy black upper housing features a clear square display window on the front that illuminates to let you verify active operation at a glance, which you can easily cross-check with your tank thermometer.
Yes. Because it uses solid-state 5V DC thermal control rather than an old-fashioned 120V bi-metallic switch, it operates at 0 dB with zero clicking or humming noises.
Every order is backed by our 30-Day Money-Back Guarantee. Submerge the MicroTherm 10W in your tank and check it against your own thermometer for a full month—if you aren't thrilled with how steadily and cleanly it regulates your water, return it for a full refund.