Tunze DOC Skimmer 9404

The Tunze DOC Skimmer delivers efficient, low-power protein skimming sized to match your saltwater aquarium’s volume.

• Recommended for marine aquariums up to 250 liters (66 USgal.)
• Immersion depth of 80 to 250 mm (3.1 to 9.8 in.) without setting.
• Dimensions without post-filter (L x W x H): 190 x 190 x 330 mm (7.5 x 7.5 x 13.0 in.)
• Water flow rate: max. 850 l/h (225 USgal./h)
• Air flow performance: 150 l/h (39 USgal./h)
• Power consumption: 8.5 W, 230V/50 Hz
• Skimmer cup volume: 0.2 liters (6.7 fl.oz.)

The Tunze DOC Skimmer 9404 pulls dissolved organic waste out of the water before it breaks down into nitrates — see our guide to Protein Skimmers for how skimming fits into overall reef water quality.

What's in the Box

TUNZE do not publish an itemised scope-of-delivery list for the 9404, so rather than guess, here is what they do publish — the spare parts they list against this model, which is a fair picture of what it is built from:

• The variable-level container, which TUNZE describe as holding a Comline® energy-saving pump 900 and a post-filter
• Comline® DOC Skimmer 9004
• Comline® energy-saving pump 900
• Post-filter, and the 300 µm nylon post-filter bag that goes in it
• Adapter ring
• Four elastic acoustic-insulation pads
• Cleaning brush

That construction explains the 8.5 W figure on the specification above: it covers both the skimmer and the circulation pump in the container. TUNZE supply the 9404 with two manuals, the Comline® DOC Skimmer 9004 manual and the Comline® Filter 3162 manual, because the container shares its housing parts with that filter.

If you need the exact box contents confirmed before you order, message us and we will open a unit and check.

Compatibility

TUNZE recommend the 9404 for marine aquariums up to 250 litres (66 USgal). This is a marine skimmer; it is not intended for fresh water.

Where it will physically fit. This is the cabinet-filter version: it stands in a sump or filter compartment rather than hanging in the display tank. It works over an immersion depth of 80 to 250 mm (3.1 to 9.8 in) with no setting to change, which is a wide window and the main reason to choose it over an in-tank model — a sump whose level swings will not upset it. The body is 190 × 190 × 330 mm without the post-filter, so measure the compartment for footprint and for the clear height above it: the skimmer cup lifts vertically out, and part of the foam reactor comes with it.

Stand it in a zone of calm water. TUNZE are specific that a drain outlet or an air ejector close by will disturb the formation of foam.

TUNZE rate every DOC skimmer against a standard marine aquarium stocked with leather corals, and publish a reduction table for tanks that carry a more sensitive biotope. Their worked examples all use a skimmer rated for 1,000 litres:

• Leather corals, long-polyp corals and anemones — no reduction. TUNZE note that the dissolved-organic load in these tanks may be higher, and is sometimes even necessary, so the skimmer can be run at its full rated volume.
• Mixed leather and stony (LPS) corals — 40% reduction. TUNZE's example: a skimmer rated for 1,000 litres should be used on a tank holding about 600 litres at most.
• Predominantly small-polyp stony corals (SPS) — 60% reduction. A skimmer rated for 1,000 litres should be used on a tank holding about 400 litres at most. TUNZE add that these tanks should carry no phosphate or nitrate load worth mentioning, and that the skimmer is often the stand-alone filtration.
• SPS with a heavy fish population — 70% reduction. A skimmer rated for 1,000 litres should be used on a tank holding about 300 litres at most.
• Comline® skimmers used as contact skimmers on plankton breeding tanks — 70% reduction. TUNZE's example here is a Comline® skimmer rated for 1,200 litres on a tank holding about 360 litres at most.

TUNZE print this table on their DOC Skimmer pages. The rating to apply it to on this model is up to 250 litres.

Safety & Precautions

These are TUNZE's own safety instructions for the Comline® DOC Skimmer 9404, from the manual supplied with it.

• Not designed for outdoor operation.
• Check that the operating voltage matches the mains supply before first use.
• Fit the mains plug higher than the unit, so water cannot run down the cable into the plug.
• Operation is permitted only with a residual-current circuit-breaker fitted, 30 mA maximum.
• Disconnect every electrical unit in the tank from the mains before working in the aquarium.
• Do not repair a damaged mains cable — replace the unit completely.
• Connecting the unit to third-party equipment such as electronic switches or speed controllers is not permissible.
• Maximum aquarium water temperature: +35 °C (95 °F).
• Keep the instruction manual.
• TUNZE state the device is suitable for users, children included, with limited physical, sensory or mental abilities, or without experience or prior knowledge, only where a responsible person provides suitable supervision or detailed instruction. Children should not be allowed to play with it.

Warranty & Support

This product carries a 24-month manufacturer warranty from the date of purchase, covering material and manufacturing defects. TUNZE’s printed instruction manual is the document that governs here: their website currently quotes a longer period, but the manual supplied in the box states 24 months, and 24 months is the term we will honour.

What voids it, and what it does not cover. TUNZE name three exclusions: damage from inexpert handling, for which water damage is the example they give; technical modification carried out by the buyer; and connection to devices they have not recommended. The remedy under the guarantee is repair or replacement of the unit at TUNZE’s discretion, and consequential damage is explicitly excluded — on an aquarium that means the unit itself is covered and what happens in the tank when one fails is not. TUNZE also require a defective unit to come back in its original packaging with proof of purchase, so keep the carton and the foam for the two years rather than putting them out with the recycling.

Warranty support is handled by us directly. Message our WhatsApp support with your order number and we will diagnose the fault first — most cases are solved by replacing a single part, so you rarely need to send the whole unit. If the item does need to come back, it ships to our Delhi or Pune warehouse, whichever one served your order, and courier cost in both directions is borne by the customer. Your GST invoice is valid proof of purchase for the claim.

Returns & Replacement

Returns are accepted within 7 days of delivery, provided the item is unused and in its original packaging. Manufacturer-sealed items cannot be returned once the seal is broken, and sale-priced items are not refundable.

If your item arrives defective or damaged, message us on WhatsApp with your order number — or email us, if you would rather — and we will replace it. Approved replacements are delivered within 3 to 5 business days. Transit damage is covered by insurance on every shipment. If tracking shows delivered but nothing reached you, tell us within 72 hours, which is the reporting window Indian couriers allow. Damage caused during installation or use is not covered; replacement spares for such cases are chargeable.

Full terms are on our Cancellation & Returns page.