de*nitrate — Natural Anaerobic Denitrification Biomedia 500 ml, 1 L and 4 L - Seachem

Seachem de*nitrate is an economical, natural, porous biomedia whose pore distribution and geometry promote both aerobic nitrification at the surface and anaerobic denitrification at the core of the media. It removes nitrate by the same process as live rock, with efficiency magnified several fold by forcing water to filter through its porous structure. No danger of hydrogen sulfide production, unlike sulfur-based media.

Main advantages

• Natural anaerobic denitrification — removes nitrate like live rock, with greater efficiency
• Dual function: aerobic nitrification (ammonia, nitrite) + anaerobic denitrification (nitrate)
• High porosity natural material — pore size well suited to anaerobic bacteria
• No danger of hydrogen sulfide — unlike sulfur-based media
• Does not get used up — a permanent biomedia as long as nitrate stays under control
• Three sizes offered: 500 ml, 1 L and 4 L

Flow rate decides everything

de*nitrate works thanks to its porous structure: oxygen is consumed by aerobic bacteria at the surface, which creates anaerobic conditions at the core of the media, where denitrifying bacteria remove nitrate.

• Below 200 L/h (50 US gallons/h): functions as both an aerobic filter and an anaerobic denitrifying filter
• Above 400 L/h (100 US gallons/h): functions solely as an aerobic filter — no nitrate removal

The manufacturer is categorical: de*nitrate absolutely must be used at a flow rate of 200 L/h (50 GPH) or less to be effective at removing nitrate. If higher flow rates are unavoidable, Seachem recommends Matrix or Pond Matrix.

Directions (Seachem)

• Rinse off the dust before use
• Place so as to assure the flow of water through it: a canister filter, chemical filtration module, box filter or media reactor
• Flow rate should not exceed 200 L/h (50 US gallons per hour)
• Once in use for several days, nitrate concentrations should start to fall and level off gradually around 4 to 5 mg/L
• As long as nitrate concentrations remain under control, the product is not exhausted
• If very high nitrates are initially present, bring them down below 20 mg/L with water changes BEFORE relying on the media
• Use enough media to remove nitrate at least as fast as the rate of formation

Yield and official dosing table

Each 500 mL of de*nitrate treats about 100 to 200 L (25 to 50 US gallons), depending on the initial nitrate concentration and the current biological load.

de*nitrate or Matrix?

Both are permanent biomedia that support denitrification, but their applications differ. de*nitrate is smaller (gravel-sized) and more efficient per volume for nitrate reduction at low flow — ideal in a dedicated reactor or a slow-flow filter. Matrix is larger (10 mm) and supports denitrification at higher flow rates — ideal in a canister or sump. The two can be combined.

Maintenance

de*nitrate does not get used up, but it can clog with detritus and biofilm. Pre-filtering the water upstream with foam or filter floss significantly extends its useful life. Rinse periodically with aquarium water if needed, without destroying the internal bacteria.

Available sizes

• 500 ml
• 1 L
• 4 L

Rounding out your biological filtration

• Seachem Matrix — the biomedia to use when your flow exceeds 200 L/h, as recommended by the manufacturer
• Seachem Stability — nitrifying bacteria to speed up colonization of fresh media
• Salifert Nitrate Test Kit — essential: the test is what tells you whether the media is working
• Seachem The Bag — the filter bag to hold the media in a box filter or a sump compartment

Frequently Asked Questions

What flow rate is actually needed for nitrate removal?

200 L/h (50 GPH) or less, no compromise. Above 400 L/h, de*nitrate remains an excellent aerobic nitrification media — it handles ammonia and nitrite — but it no longer removes nitrate. The manufacturer points to Matrix in that case.

Does de*nitrate work if you simply drop it in the sump?

Placed loose in a sump, flow is generally too high for denitrification: the media then acts as an aerobic filter. To target nitrate, you need a compartment or reactor where the flow passing through the media stays below 200 L/h. It is the flow through the media that matters, not the total system flow.

My nitrates are very high — will de*nitrate bring them down on its own?

The manufacturer asks that nitrates first be brought below 20 mg/L with water changes. The media is designed to remove nitrate at the rate it forms, not to catch up on a major accumulation. Once the level is brought down, it holds it around 4 to 5 mg/L.