Finnex HMS-300S 300 W Digital Titanium Aquarium Heater

Exact-model photograph is not verified. Text-only reference. The registered official HMS family image shows a titanium heater, controller, and separate probe, but it does not identify the 300 W size or an exact package; it is not presented as the selected model photograph.

Finnex’s HMS-300S is a manual-defined 300 W digital titanium heater for an 80–100 US-gallon range, with a separate remote water sensor and a 50–94°F setting range. The available evidence does not verify an individual current retail SKU, complete supply nameplate, seller package, or wattage-specific photograph, so this is a model-reference lookup—not a finder match or a claim about a live offer.

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 HMS manual names HMS-300S as a distinct 300 W model row and lists 2.70 A at a 115 V reference. That current draw is not a complete supply-voltage or frequency rating.
• Finnex gives this model an 80–100 US-gallon band and a 12.40-inch tube. In the same table, HMS-200S is 200 W with an 11.22-inch tube and a 60–80-gallon range, while HMS-500S is 500 W with a 15.16-inch tube and a 100–120-gallon range. The touching 80- and 100-gallon endpoints do not make the models interchangeable.
• The exact table lists a 55-inch power cord, a 39-inch controller-to-heater cord, and a 47-inch remote-sensor cord. Those distinct lengths can help with layout planning but do not replace checking the actual tank, outlet, and water path.
• HMS uses a separate remote water sensor rather than the HMH family’s in-tube sensor arrangement. Finnex directs the user to keep the probe submerged just above the heater, directly below its cord clip with no slack, near moving water; the manual also describes aquarium or sump placement.
• The manual specifies an adjustable 50–94°F digital setting in 0.1°F increments and states ±0.5°F display accuracy. These are manufacturer display specifications, not an independent measurement of tank-water stability.
• HMS low-water protection operates only from 58–92°F. The manual says this system is disabled outside that range and warns that the heater may continue heating if the sensor is exposed; the protection should not be treated as active at every possible setpoint.
• Finnex describes HMS for freshwater and marine aquariums and separately requires operating water above 150 ppm TDS. Both statements matter; water type alone does not establish suitability for a low-TDS setup.

Limits to weigh

• No individual current HMS-300S retail SKU, UPC, Shop variant, seller offer, or delivered package was verified. The official collection and search are bounded source checks, not proof of absence.
• The manual reports 2.70 A at 115 V but does not provide the complete allowed supply-voltage range or frequency for this configuration. Read the actual product nameplate and its own instructions before electrical decisions.
• The documented range begins at 80 gallons. The current finder’s maximum-only volume rule cannot enforce that lower boundary, so this configuration remains reference-only and must not match smaller aquariums just because they fall below 100 gallons.
• The low-water alarm/cutoff is not active outside its documented 58–92°F range. Do not assume it protects an exposed probe at lower or higher settings.
• The manufacturer’s accuracy statement concerns the display; it is not a test of temperature uniformity or stability in a particular aquarium. A separate thermometer and the manual’s installation/maintenance steps still matter.
• No exact 300 W HMS product/package photograph was verified. The registered family visual does not identify the selected wattage or an actual seller package.
• The reviewed sources do not establish inline external-filter compatibility or a specific seller’s package contents.

Check before ordering

• Check that the unit, selected listing variation, and carton identify Finnex HMS-300S at 300 W. Do not substitute HMS-200S, HMS-500S, or a different Finnex family.
• Compare the full 80–100 US-gallon manufacturer band—including its 80-gallon lower edge—with the actual tank and operating conditions. This site intentionally does not treat the upper limit alone as a fit recommendation.
• Inspect the actual unit’s voltage/frequency nameplate and model-specific instructions. The manual’s 2.70 A at 115 V entry does not establish a complete supply rating.
• Confirm the particular seller package actually includes the remote sensor/controller and protective parts needed for the HMS setup; the family/manual evidence does not authenticate any seller’s shipped bundle.
• Plan for the documented cord lengths and probe placement, keeping the separate sensor submerged just above the heater with no slack and using the required moving-water location.
• If low-water protection is important, check the intended setting against its 58–92°F active range and follow Finnex’s sensor-care and reset directions; do not rely on protection outside that range.
• Check that the water will meet Finnex’s stated TDS-above-150-ppm condition, whether the setup is freshwater or marine.