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New approach — ammonium and urea as nitrogen sources

Deep dive Published: 30 May 2026

Why this topic has come to the forefront now

The nitrate article noted that corals can use several forms of nitrogen, and that nitrate is energetically the most expensive of these. This observation has been known to researchers for decades — Grover, Maguer, Allemand and Ferrier-Pagès published a series of papers on Stylophora pistillata nitrogen uptake kinetics from 2002–2008 at the Centre Scientifique de Monaco. The knowledge is therefore old.

What has happened in recent years is that the hobbyist community has started taking this research seriously and experimenting with it in practice. In early 2024 Reef Builders published Michael Paletta’s article on ammonium dosing. In April 2025 Salem Clemens published the same magazine’s DON/DIN Rabbit Hole article, which compiled the peer-reviewed research basis into a form accessible to hobbyists. Salem has since founded his own company Novel Aquatics, through which future research and product launches proceed. Meanwhile, Colorado speciality stores Underwater Wonders and Top Shelf Aquatics had begun using AquaVitro Synthesis (a freshwater plant fertiliser containing ammonium, nitrate and urea), and the results in Acropora colouration were so remarkable that news spread quickly through the community.

By spring 2026 this discussion is no longer an experimental curiosity — a strong research foundation has formed around the topic, the first commercial products have appeared, and the hobbyist community’s practical experience is growing month by month.

This article covers what the current best knowledge says, what is purchasable on the EU market right now, and why Riuttareef is watching cautiously rather than recommending aggressive changes.

Nitrogen forms — why nitrate is not what corals prefer

At the deep-dive level it is worth pausing at the biochemistry. A coral cell does not take up nitrogen via a single general route — every nitrogen form has its own transport and assimilation process, and the energetic costs of these differ significantly.

Ammonium (NH₄⁺) is transported across the cell membrane via AMT-family membrane proteins. Inside the cell it is directly attached to glutamate via the enzyme glutamine synthetase (GS), producing glutamine. This gives rise to amino acids for protein construction. The route is direct and energetically cheap: one ATP molecule per assimilated N atom.

Urea (CO(NH₂)₂) enters through the cell membrane either passively (small neutral molecule) or via active membrane proteins. Inside the cell, the enzyme urease breaks urea into two ammonia molecules and one carbon dioxide molecule. Urease’s cofactor is nickel — a biochemical detail with significant implications for calcification. The ammonia released from urea breakdown neutralises protons produced during calcification, and the released CO₂ goes directly to zooxanthellae photosynthesis. In other words, one urea molecule feeds both the coral community’s nitrogen needs and its calcification reaction’s energy economy.

This is why urea is not just “a viable alternative” but a biochemically particularly advantageous form of nitrogen for building corals. Experimental measurement in Stylophora pistillata shows that most urea uptake occurs directly into the coral community rather than through symbionts, and three French experiments from 2006–2018 (Grover et al.; Biscéré et al.) have shown that the urea + nickel combination accelerates calcification rate significantly compared to ammonium alone.

Nitrate (NO₃⁻) requires two-stage reduction before it can be used. First nitrate reductase (cofactor molybdenum) reduces nitrate to nitrite, then nitrite reductase reduces nitrite to ammonium. Only at the ammonium stage can nitrogen be attached to glutamine. The whole chain consumes eight electrons per N atom — roughly eight times more reducing power than direct ammonium assimilation.

This does not mean nitrate is “bad” — it means the coral community invests significantly more energy in using it than in using other nitrogen sources. Energetically it is the last resort.

Amino acids are a separate matter. They are taken up directly via membrane proteins and used as-is for protein building. But amino acids also have another role: they act as infochemicals. When a coral is stressed, amino acids are released from its tissue, and Vibrio-group pathogenic bacteria have evolutionarily learned to chemotax toward this signal. The routine dosing of bottled amino acid supplements into a stable tank is — in Salem Clemens’ (Novel Aquatics) words — like a chemical beacon guiding pathogenic bacteria directly to the corals — the risk may outweigh the benefit except in special cases such as corals recovering from STN/RTN, surgery or transport.

The scientific evidence — four studies worth reading

Burkepile, Shantz, Adam et al. (2019) followed Acropora and Pocillopora colonies on natural reefs in Mo’orea for three years, adding either nitrate or ammonium to some colonies. The result was unambiguous: nitrate addition increased colony bleaching susceptibility under thermal stress, with mortality strongly elevated both short and long term. Ammonium addition instead increased zooxanthellae populations and improved colony heat tolerance. This study was the first to show that “nitrogen” is not a uniform variable on coral reefs — the form determines the direction of the effect.

Marangoni, Ferrier-Pagès, Rottier et al. (2020) brought the same idea to the laboratory level. They directly measured oxidative stress (reactive oxygen species, ROS), zooxanthellae density, chlorophyll and calcification rate under different nitrogen treatments. Nitrate increased ROS and impaired calcification even without external stress. Ammonium reduced ROS and increased both symbiont density and calcification. The researchers explicitly recommended in the article conclusions: if nitrogen is dosed to corals, ammonium is a better option than nitrate.

Biscéré, Ferrier-Pagès, Grover et al. (2018) focused on the urea + nickel combination. They showed that urease enzyme activity is limited by nickel availability — and since nickel is typically in very small concentrations as a trace element, full utilisation of urea requires both to be available. The urea + nickel combination significantly accelerated calcification and photosynthesis rates. This is one reason why modern trace element dosing protocols include small amounts of nickel — not just as a general trace element but as a urease cofactor.

Crandall & Teece (2011) measured urea’s natural concentrations on Caribbean coral reefs. The result was surprising: on oligotrophic reefs urea concentration can be up to 20 times higher than ammonium or nitrate concentrations. Urea is therefore not just “alongside other sources” — on natural reefs it is often the dominant dissolved nitrogen form. Coral communities have thus adapted through evolution to take up urea, not nitrate, as their primary nitrogen source. In the aquarium the situation reverses, because ammonia-oxidising archaea and nitrification bacteria convert all nitrogen to nitrate eventually — the original ammonium and urea cloud disappears within seconds.

Fauna Marin and Coral WOW! — the first wave product on the EU market

Fauna Marin is one of Germany’s oldest reef speciality brands and one of the few that openly publishes their own research and reference values. Their nitrate page’s official position is unambiguous — corals prefer to take up ammonium, and nitrate must first be reduced before it can be used. This statement has been on Fauna Marin’s website since 2020.

In 2024 Fauna Marin launched a product called Coral WOW!, which is essentially a concrete implementation of this principle. The product composition is officially registered: water, ammonium compounds, trace elements, marine biopolymers, coral-specific biomodulators. The dosing instruction is very conservative: 0.5 ml per 100 litres, up to four times daily. The small dose size is an important detail — a small but continuous ammonium stream compensates for nitrification rapidly converting ammonium.

Coral WOW! is essentially a DIY recipe packaged as a commercial product. Its ammonium carbonate base matches the chemistry of Randy Holmes-Farley’s original DIY recipe, but with added trace elements and organic matrices supporting coral absorption. The product is widely available in the EU at approximately €40/litre.

The second, older product in this category is Tropic Marin Plus-NP, originally designed as a nitrogen and phosphorus source for ultra-low nutrient (ULNS) tanks. Tropic Marin officially confirmed in community discussions that Plus-NP contains most of its nitrogen as ammonium and organic nitrogen compounds, not nitrate — only a small portion is nitrate-based. This is an important detail: many hobbyists have been using Plus-NP for years not knowing they are actually dosing ammonium and organic nitrogen.

EU-available commercial products in spring 2026

Fauna Marin Coral WOW! is the clearest pure ammonium-based product. EU availability is broad and price is reasonable. The product is compatible with the Balling Light system.

Tropic Marin Plus-NP is its German sibling with a slightly different composition — primarily ammonium and organic nitrogen, small portion nitrate, bound in an organic energy matrix. Originally intended for ultra-low nutrient conditions, but in practice it has worked for many hobbyists as nutrient pair balancing without aggressive impact.

Tropic Marin Amino-Organic is an amino acid-based product that also contains other organic nitrogen compounds but no nitrate or phosphate. Hans-Werner Balling, Tropic Marin’s scientific director, confirmed in community discussions that this product is intentionally built to avoid nitrate’s negative effects.

Fauna Marin Amin falls in the same category — amino acids and other nitrogen compounds, designed to complement the nutrient pair without a nitrate spike.

Microbial Marine NITROUS is the newest entrant. The product is distributed by Two Fishes and driven by Salem Clemens (Novel Aquatics). The composition is an ammonium + urea combination — the first commercial product to cover both of the most directly advantageous nitrogen sources for corals. The product is in the launch phase for North American markets in early 2026, and EU availability will likely open in the second half of 2026. Riuttareef is actively monitoring.

AquaVitro Synthesis is a Seachem product, originally a freshwater plant product, containing a mixture of ammonia, nitrate and urea. It has been used in the US reef community in recent years “by accident” — discovered through experimentation. EU availability is limited. Coral WOW! and Plus-NP are closer to the EU hobbyist and better supported.

Measurement difficulty — a central limitation

This is the single biggest reason why Riuttareef is cautious about aggressively recommending ammonium or urea dosing: hobbyists cannot reliably measure these parameters.

Ammonium moves through a reef aquarium very quickly. Both ammonia-oxidising archaea (AOA) and nitrification bacteria (AOB and NOB) oxidise ammonium to nitrite and then to nitrate within seconds or minutes. A Salifert or Red Sea consumer test typically gives a zero reading for ammonium even when dosing has been underway — which is a good thing, because if ammonium were visible in the test, the level would already be too high for the ecosystem and toxic to fish.

Urea is a different case. There is no hobbyist-level reliable test for it at all. The only practical tool is Triton laboratory’s N-DOC package, which measures total organic nitrogen and DOC separately with a full carbon analyser.

So how is dosing monitored? The answer is trend, not a single measurement:

Riuttareef’s view and the precautionary principle

Riuttareef actively follows this discussion and sees real scientific and practical merit in it. But promising is not the same as ready. In spring 2026 we still do not know: what the correct doses are for different tank sizes and livestock over the long term; how long-term ammonium or urea dosing affects microbiome composition and stability; whether urea accumulation could be an imperceptible risk to the hobbyist.

Practical conclusion: stable tank first, experiments after. This is the single-variable philosophy applied to this topic.

A concrete path for an experienced hobbyist considering an experiment:

Step 1 — foundation. At minimum 12–24 months of stable tank. ICP rhythm running. Nutrient pair (NO₃ + PO₄) reading stably in normal reference range. Corals growing and colouring well in the baseline setup. This is the starting point.

Step 2 — justified reason. Check why you want to experiment. If the tank has a specific problem this might solve — e.g. stubbornly dark SPS colouration, Acropora slow growth without explanation, chronically elevated nitrate without aggressive export — the experiment is justified. If you just “want to try,” that is not a justified reason to interfere with a stable system.

Step 3 — one variable at a time. Do not combine the change with anything else. One thing at a time, so ICP data and the tank’s response remain interpretable.

Step 4 — small starting dose. Start clearly below the manufacturer’s recommended level. With Coral WOW! for example 0.25 ml per 100 litres once daily — a quarter of the maximum recommended dose. Run for two weeks, measure NO₃ and PO₄ weekly, observe corals daily.

Step 5 — gradual increase. If after two weeks everything is fine, increase the dose by 25 % and watch for the next two weeks. Repeat. The target dose is typically reached over 2–3 months, not in weeks.

Step 6 — long-term monitoring. At least 6 months of ICP trend from when dosing started, preferably 12 months, before any conclusions are worth drawing.

This article is aimed at experienced hobbyists with an ICP routine and experience interpreting their tank’s biology. For beginners, the main element articles (alkalinity, calcium, magnesium, phosphate, nitrate) and internalising the stability principle are recommended first — they are the foundation without which this topic is not yet relevant.

Sources

Peer-reviewed studies

Hobbyist literature and brand documentation

Books and textbooks