Finnex HMH-100S 100 W Digital Titanium Aquarium Heater

Exact-model photograph is not verified. No wattage-specific HMH product or package photograph was verified. The official HMH family artwork and manual diagram identify a series, not this selected model or delivered package; this model-reference entry is text-only.

Finnex’s September 2020 HMH table names this 100 W configuration for 20–30 US gallons, with a 7.68-inch tube and a 30-inch controller lead. The 20-gallon minimum is not enforced by the finder, and no individual current retail variant was established, so this is for checking an exact label—not a tank-fit recommendation.

Search results may include other models. Confirm the exact model, applicable region, condition and included parts before ordering.

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Documented model details

• The exact manual row lists HMH-100S at 100 W for 20–30 US gallons. Its 7.68-inch tube is shorter than the 200/300/500 W rows; the listed power, controller-to-heater, and sensor cords are 47, 30, and 47 inches.
• Finnex specifies a 50–94°F range with 0.1°F adjustment and ±0.5°F stated display accuracy. The family design uses an internal temperature sensor in the tube, not the remote-sensor arrangement of the separate HMS series.
• The maker describes titanium construction, a guard and freshwater/marine use, while requiring water above 150 ppm TDS. Its manual also describes fully submerged installation and places the low-water sensor where the heater joins the cord.

Limits to weigh

• The manual’s 20-gallon lower edge cannot be expressed by the current maximum-only finder. The 20-gallon endpoint also appears on the adjacent 50 W HMH row; this reference does not choose between them or approve a particular tank.
• 0.90 A is listed at 115 V, not as a complete supply rating. Exact voltage/frequency on the heater or package, retail SKU/UPC, included parts and current seller package remain unverified; the Shop search omission is not evidence of discontinuation.
• The manual’s low-water warning operates only from 58–92°F; it is disabled outside that interval, and the instructions warn that heating can continue while the sensor is out of water outside the warning range. Do not treat it as universal dry-run protection.
• Finnex’s family TDS condition is not checked by the finder. No wattage-specific HMH-100S product/package photo was verified, so the lookup is text-only; manufacturer claims are not independent performance tests.

Check before ordering

• Check the item and carton for the exact HMH-100S / 100 W identity; do not substitute the HMH-50S or another wattage based on a family image.
• Read 20–30 US gallons as a two-sided published band. At 20 gallons, the manual also lists the neighboring 50 W row; the model lookup does not resolve heater sizing for a specific aquarium.
• Inspect the actual electrical label and supplied manual for the complete input rating, seller package and included controller/cables; 0.90 A at 115 V is not a complete voltage/frequency specification.
• Before operation, follow the HMH immersion, flow, sensor-position, drip-loop/GFCI and maintenance instructions. Confirm water exceeds Finnex’s stated 150 ppm TDS threshold and note the limited 58–92°F low-water warning window.