Finnex HMU-300S 300 W Digital Titanium Aquarium Heater

Exact-model photograph is not verified. This reference page is text-only; the standard model review retains the official HMU-family visual showing a tube, separate guard, digital controller, and remote sensor. The artwork has no model/wattage/package label and does not identify the selected 300 W assembly or seller shipment.

Finnex’s captured US Shop data identifies the 300 W option as HMU-300S (variant 49216059048235); the grouped record title says HMU, while its legacy URL slug retains HMX and a 150 W option string. The exact structured 300 W variant resolves this identity. Finnex’s chart covers HMU 100–500 W but gives no aquarium-capacity range. This model cannot be matched to tank size from wattage alone and remains reference-only; the available image is HMU-family imagery, not an exact 300 W package photo.

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

• Finnex's US Shop product JSON assigns its 300 Watts choice the exact SKU HMU-300S, Shopify variant ID 49216059048235, and parent product ID 9526613344555. The variant barcode field is blank. The title and selected variant identify HMU, despite HMX and 150 W strings in the legacy URL slug; the slug is not used to rename or merge the exact variant.
• The official comparison chart lists an HMU range of 100–500 W and marks that family span with a titanium heating tube, steel coil, push control, digital display, 68–92°F range, non-resumable fuse and Japanese components. These are manufacturer family claims, not independent tests or a wattage-specific difference. The chart does not include the separately listed 50 W option.
• The grouped Shop description claims a remote temperature sensor, adjustable digital controller/display and flame-retardant guard. Those shared family descriptions do not provide a 300 W tank-size band, heater dimensions, exact installation route, or a full safety assessment of the fuse or guard.
• No aquarium capacity or gallon range for the 300 W option appears in the reviewed Shop variant data or comparison chart. The wattage alone is not used to derive a tank-volume recommendation.
• The official Shop gallery image is mapped to the HMU series as a family visual. It shows a heater tube, separate guard, controller and sensor, but has no 300 W label or exact package identity.
• The reviewed Finnex instructions index visibly listed HMH, HMS and HPC heater manuals, not an HMU manual. Instructions or operating limits from those other Finnex families are not transferred to HMU-300S.

Limits to weigh

• The primary sources do not give a model-specific aquarium-volume range or heater length for HMU-300S. Do not convert 300 W into a gallon recommendation or treat it as compatible with a particular aquarium without a supported sizing source.
• The exact variant SKU is documented, but its barcode field is null; no UPC is established. The full supply voltage and frequency were not verified. Check the physical unit's complete electrical label and the exact instructions before installation.
• The reviewed instruction index did not list an HMU-specific manual, and the shared page description is not a substitute for installation directions. Water-type approval, placement, immersion details and operating constraints remain unknown; do not infer them from other heater families.
• Finnex's chart gives a 68–92°F HMU family range, but the sources do not provide a numerical control-accuracy specification or independent in-aquarium measurements. The stated setting range is not a promise of tank-wide stability or animal-care suitability; independently check water temperature and consult appropriate husbandry guidance.
• The manufacturer describes a non-resumable fuse, but the reviewed sources do not supply HMU-specific failure behavior or full setup precautions. Do not treat the fuse claim as permission to run the heater dry or disregard the missing installation instructions.
• A product-specific Amazon search returned HTTP 503 before search results, an ASIN or package could be inspected. That failed request does not establish that no listing exists. Keep any destination labelled as a fixed full-model search, not a verified exact listing; no price, stock, seller or delivered package is asserted.
• The official image is only an HMU-family visual and does not identify the 300 W option, exact assembly, dimensions or package. It must not be presented as a wattage-specific product photograph.

Check before ordering

• Check that the offered model and delivered unit identify Finnex HMU-300S / 300 W. The official variant record gives SKU HMU-300S and its own variant ID; do not substitute a neighboring wattage or infer HMX from the stale URL slug. No UPC was verified.
• Do not use 300 W alone to select an aquarium size. The reviewed primary sources publish no capacity range for this variant, so verify sizing against an exact authoritative instruction or qualified aquarium-heating guidance before relying on it.
• Confirm the actual unit's complete voltage and frequency label and obtain HMU-specific installation directions. Water type, placement and immersion conditions are not resolved by the family description or by manuals for other Finnex heater lines.
• Treat the chart's 68–92°F span and control claims as manufacturer specifications, not measured water temperature or a livestock target. Use an independent thermometer and appropriate care guidance.
• If using the official image for visual identification, remember it shows HMU-family components rather than a labeled 300 W model or delivered package. Verify the exact SKU and included parts from the seller's current description and shipment.
• The exact Amazon listing was not verified after a 503 response. If following the fixed brand-plus-full-model search, check the exact model, seller, package and return terms before ordering; the search is not an exact product match and no current price or availability is claimed.