2Hr Aquarist APT e

Q: Which should I use - APT e or APT 3?

The simplest way to decide is by your substrate and how hands-on you want to be. APT 3 is nitrate-limiting: growth is a little slower, algae risk is lower, and maintenance is more forgiving, which makes it the better match for nutrient-rich soil or anyone wanting a steadier tank. APT e supplies nitrate and phosphate in full, so plants grow faster - but that pace assumes strong CO2, good flow, and consistent dosing, and it leaves less margin for error. Choose APT e if you run an inert substrate or a high-energy tank and you're comfortable staying on top of maintenance; choose APT 3 if you have nutrient-rich soil or prefer an easier routine. (APT 1 is the starter step for the first one to three months on fresh soil.)

Q: I'm using APT e and I'm getting algae - is it too strong?

APT e isn't "too strong" on its own, but it does assume the rest of your tank is keeping pace. Because it doses nitrate and phosphate in full, it's built for tanks with strong, stable CO2, good circulation, and enough plant mass to use those nutrients. Early-stage algae usually points to the tank not yet being balanced -CO2 fluctuating, flow reaching only part of the tank, or a young tank still maturing - rather than to the fertiliser itself. If you're in the first few weeks, or your setup is more moderate, APT 3 or APT 1 is often the steadier choice while things settle.

Q: Can I mix or combine APT e with APT 1 or APT 3?

Yes. Because APT 1 carries no nitrate or phosphate while APT 3 and APT e do, blending APT 1 with either gives you a middle ground - more nitrogen and phosphate than APT 1 on its own, but less than a full dose of APT 3 or APT e. It's a useful way to fine-tune how lean or rich your dosing is: lean toward APT 1 in the mix for tighter algae control and nitrate limitation, or toward APT e for faster growth. You can adjust the ratio to suit your tank rather than treating the three as mutually exclusive.

€21,90

2Hr Aquarist APTe replicates the famous nutrient dosing approach pioneered by Tom Barr in a ready-to-use concentrate that removes the guesswork from trying to recreate this powerful and sometimes elusive formula.

INSTRUCTIONS

3ml / 100L per day
0.07 fl oz / 26 USgal per day

Dose any time of day, consistently.
Minor sedimentation / crystallization is normal.

WHY

The EI approach pioneered by Tom Barr is designed to provide a unlimited / unconstrained amount of nutrients to plants based on a professionally Estimated Index of their needs. APTe provides a calibrated version for richer coloration and algae control.

INGREDIENTS

GUARANTEED ANALYSIS
Total Nitrogen (N)........................................... 2.0%
2.0% Nitrate Nitrogen
Available Phosphoric Acid (P2O5)....................1.37%
Soluble Potash (K2O)....................................... 8.0%
Magnesium (Mg)............................................. 1.60%
Iron (Fe) ...........................................................0.16%
0.16% Chelated Iron
Derived from: Potassium Sulphate, PotassiumPhosphate, Potassium Chloride, MagnesiumNitrate, Magnesium Sulphate, DTPA Iron, EDTA Iron, EDDHA Iron

Further information here.

Product variants

2Hr Aquarist APT e

Standard

€21,90

6X Power

Example of APT's relative concentration compared with a 50-year old European 'big brand fertiliser'. APT contains 5X the amount of Phosphorus (P) and 6X Potassium (K) per ml. That is like having 5 shots instead of 1 in your morning espresso, if you are into coffee :)

Optimal Balance

Simply 'more' is not always better. Lower Nitrogen (N) delays chlorophyll production and promotes richer colors- up to a point. Nitrogen is also essential for metabolism. APT pushes the limits of that balance. Maximum color before diminishing returns.

Superior Form

Similar to food labels, "20% protein" or "1% Iron" tells little about actual absorbability, efficacy, and impact. APT's components are up to 50X more absorbable and accessible across a wider range of pH and other water parameters.

Dosage

Use the Dosage Calculator. Absolute precision isn't necessary: when in doubt, dose slightly less, not more. Consistency is much more important than being 100% accurate.

Timing

Changing fertilizers can trigger a temporary system shock. In rare cases, this results in widespread algae. This can be mitigated by introducing APT incrementally over 2 weeks.

Switching?

Changing fertilizers can trigger a temporary system shock. In rare cases, this results in widespread algae. This can be mitigated by introducing APT incrementally over 2 weeks.

Which APT?

APT 1 is perfect for tanks with more fish, fewer plants. Also for new tanks (<3 months) with aquasoil. Enjoy comprehensive nutrition without nitrates and phosphates for maximum algae control.

APT 3 is perfect for tanks with more plants, fewer fish. Enjoy 100% comprehensive macro, micro and trace minerals. Unlocks the full potential of the hobby's most demanding plants.

APT e is perfect for heavily planted Dutch Style tanks and users who understand EI methodology. Supremely concentrated and expertly balanced.

Deeper Reds Built-In

APT 3's nitrate-limiting ratio is specifically engineered to bring out deeper reds in species like Rotala rotundifolia and Ludwigia arcuata, while still providing everything plants need to thrive.

Modern Plant Science

APT's proprietary Capstone formulation was developed specifically for today's planted aquariums, factoring in current tank environments, new plant hybrids, and evolving light and CO2 technologies, unlike conventional fertilisers that trace their origins to 1970s fish-focused tanks.

FAQs

Please read our FAQs page to find out more.

Which should I use - APT e or APT 3?

The simplest way to decide is by your substrate and how hands-on you want to be. APT 3 is nitrate-limiting: growth is a little slower, algae risk is lower, and maintenance is more forgiving, which makes it the better match for nutrient-rich soil or anyone wanting a steadier tank. APT e supplies nitrate and phosphate in full, so plants grow faster - but that pace assumes strong CO2, good flow, and consistent dosing, and it leaves less margin for error. Choose APT e if you run an inert substrate or a high-energy tank and you're comfortable staying on top of maintenance; choose APT 3 if you have nutrient-rich soil or prefer an easier routine. (APT 1 is the starter step for the first one to three months on fresh soil.)

I'm using APT e and I'm getting algae - is it too strong?

APT e isn't "too strong" on its own, but it does assume the rest of your tank is keeping pace. Because it doses nitrate and phosphate in full, it's built for tanks with strong, stable CO2, good circulation, and enough plant mass to use those nutrients. Early-stage algae usually points to the tank not yet being balanced -CO2 fluctuating, flow reaching only part of the tank, or a young tank still maturing - rather than to the fertiliser itself. If you're in the first few weeks, or your setup is more moderate, APT 3 or APT 1 is often the steadier choice while things settle.

Can I mix or combine APT e with APT 1 or APT 3?

Yes. Because APT 1 carries no nitrate or phosphate while APT 3 and APT e do, blending APT 1 with either gives you a middle ground - more nitrogen and phosphate than APT 1 on its own, but less than a full dose of APT 3 or APT e. It's a useful way to fine-tune how lean or rich your dosing is: lean toward APT 1 in the mix for tighter algae control and nitrate limitation, or toward APT e for faster growth. You can adjust the ratio to suit your tank rather than treating the three as mutually exclusive.

The 2Hr Way

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June 19, 2026
0 commentson Good parameters, Good CO2, Good light, Poor plant growth?

Good parameters, Good CO2, Good light, Poor plant growth?

This article explains why aquatic plants sometimes do not grow well in a planted aquarium despite having good growth parameters available. It demonstrates how clearing old growth above and below the substrate allows new growth to be rejuvenated better than just trimming.