OASE BioMaster 2 Thermo 850 External Filter with HeatUp 400 review

Bottom line: OASE's BioMaster 2 Thermo 850 is the largest observed US Thermo configuration in this family: full-unit SKU 94677 with an included HeatUp 400 heater. The current exact US product page lists an upper aquarium-volume label of 225 gallons / 850 litres. That figure and a single manual recommendation do not create a lower-to-upper tank range, prove a stocking level or show how the filter performs in a particular installation. This is a source-based assessment, not a hands-on test.

Identify the complete Thermo configuration

The exact product page names BioMaster 2 Thermo 850 and SKU 94677. OASE's included-components section separately identifies the BioMaster 2 850 filter body, SKU 94697, and HeatUp 400 heater, SKU 77117. The full Thermo package is a real functional variant of standard BioMaster 2 850, not a duplicate: the standard 94697 configuration does not include that heater. Check the full Thermo number on the item and invoice if an included heater is part of the purchase decision; a seller-created kit with a separate heater is not automatically the same configuration.

OASE describes the 850 as an external canister with a priming button, a removable EasyClean pre-filter, foam stages and Hel-X biological media. The maker says the pre-filter can be removed separately, and describes safety locks and automatic shutoff intended to reduce unwanted leakage during that service. The published 8 L field is labelled total filter volume; the separate pre-filter field is 0.70 L. Neither is a sourced media-basket capacity, so the 850 remains unverified for a hard basket-litre requirement even though those numbers may look large.

Location, footprint and power

The exact North American operating manual applies to US SKU 94677 and says the filter may be installed next to or under the aquarium, with attention to maximum head height. It does not require a below-tank cabinet, but it also does not certify a specific shelf, hose path or stand. The product page lists the body at 9.4 × 9.4 × 22 inches with a 13-foot hose; allow extra room above and around it to reach the head, disconnect hoses and lift the EasyClean module for maintenance. Confirm supports, electrical safety and the manufacturer's current head instruction before fixing a position.

The manual's North American table lists 120 V / 60 Hz, 25 W for the filter, and 400 W for the Thermo heater. The exact page labels a combined line “32 + 400 W,” which does not match that manual's separated component values. Keep both records visible if electrical planning depends on the total; do not turn the page's combined label into a derived fact. The exact US page also describes the included heater as adjustable. Heater operation, placement and temperature should be checked in the supplied HeatUp instructions for the actual set-up.

What the 850 label does and does not say

The current US item page reports up to 225 US gallons / 850 litres; the exact US manual lists 225 gallons / 850 litres as its recommended aquarium volume. A prior official-page extraction in the saved research reported 220 gallons, but the current exact product route now directly displays 225 and the applicable manual independently lists 225 as the recommendation. This assessment records the current exact-page ceiling as 225 while preserving the earlier extraction as a historical discrepancy. No source provides a lower endpoint in the reviewed record, so entering a tank volume cannot be treated as a verified interval match for this model.

The source documents also disagree on flow and head details: the current exact US route lists 400 gallons per hour / 1,500 L/h and 7.4 feet / 2.25 metres, while the applicable manual lists 400 gallons per hour / 1,550 L/h and 7.4 feet / 2.2 metres. Do not read either maximum as measured output through a real hose/media arrangement. Since OASE's routes are not fully aligned, the research record leaves a chosen flow and maximum-head matching value unset rather than ranking the 850 from one preferred figure.

Neither the gallon ceiling, total filter volume nor advertised flow establishes support for a high-waste tank or a particular fish count. The product material reviewed here gives no model-specific high-bioload rating. Treat husbandry, stocking and maintenance as separate decisions; when unusually heavy waste is essential to the purchase decision, ask for exact manufacturer guidance rather than inferring it from “850.”

Compare it with the standard 850 and smaller Thermo models

Standard BioMaster 2 850 SKU 94697 is the closest alternative when the filtration platform is wanted without an included heater. Thermo 850 SKU 94677 adds the specified HeatUp 400 as part of the configuration; whether that is useful depends on the aquarium's heating plan and electrical setup. Thermo 600 has a smaller body and included HeatUp 300. The Thermo 250 and 350 include different heaters again. These differences affect what arrives in the box, dimensions and published power entries, so the size suffix alone is not enough to identify the product.

The removable pre-filter may appeal to someone who values a separate first-stage service step, but OASE's convenience language is not an independent service-time test. The buyer still needs to follow the manual's shutdown/cleaning procedure, protect electrical connections from water, and preserve room for the full module to come out. A 22-inch housing in a tight stand can be an installation mismatch even when the total aquarium volume falls below the manufacturer's ceiling.

Buying checks

Before choosing this unit, confirm US SKU 94677, the included HeatUp 400, the exact filter/media/hose package and the North American 120 V / 60 Hz label. Check the current manual against actual height, hose route, head and service access; do not use standard 850 specifications to fill a Thermo field without a SKU-specific bridge. If a complete numeric tank interval, basket capacity, confirmed flow/head or high-waste rating is essential, the reviewed records do not establish it. No personal ownership, aquarium outcome, laboratory measurement, current price or stock claim is made here.