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2Hr Fertiliser FAQs


1. I want to start a new aquarium without CO2 injection.

Without CO2 injection, algae has an edge. Go for APT 1 “Zero”.

Remember that in low CO2 environments, it takes 3-4 weeks for the impact of better nutrition to show. It is normal for new plants to shed old leaves as the plant adapts to the new tank. Watch for new growth. If these are present and healthy, you are on the right path.

2. I want to start a tank with CO2 injection.

Go for APT 1 “Zero” for the first 1-2 months.
As plant mass increases, switch to APT 3 “Complete’ if your fishload is low-moderate.
Continue with APT 1 “Zero” if your fishload is high (if NO3 measures above 8ppm at the end of a regular week before water change).

We also recommend enriching your substrate with APT Jazz after 2 months. Plants absorb nutrients from both leaves and roots. For hardy plants, you can get away with water- fertilization. For more demanding species, root fertilization makes a big impact.

3. I want to rejuvenate my existing aquarium.

Aquatic plants are not perennial so simply adding a new, more powerful fertilizer will not do.

Old stems, roots and leaves must be removed. APT will help in generating NEW growth, but cannot rejuvenate deteriorating leaves / stems. For mature tanks with low to moderate fishload, use APT 3 “Complete”.

The nutrients in substrate naturally deplete over 3-6 months. Use APT JAZZ to restore and rejuvenate your substrate.

4. I want to get rid of algae.

While APT fertilizers are designed to reduce algae occurrence, they will not by themselves remove algae.

APT fertilizers works by enabling plants to successfully outcompete algae, the same way that trees in a forest outcompete weeds for light and nutrients.

APT also smartly controls the amount of nutrients that trigger algae, while providing enough for healthy plant growth. We suggest reviewing the causes of algae, and the detailed guides on managing specific types of algae.

To remove algae, use APT FIX, which is highly effective.


1. How does APT work?

The planted aquarium hobby traces its roots to fish-focused aquariums in the 1970s. Conventional fertilisers were developed for (and continue to serve) hobbyists looking to supplement fish tanks with hardy plants.

Conversely, APT was developed for today's planted aquariums. Its proprietary CapstoneTM nutrient formulation factors in current tank environments, with today's new plant hybrids and evolving light and CO2 technologies. It has been tested to bring out richer colors and stronger growth in the most demanding aquatic plants.

APT 3 “Complete” was crafted based on the study of 2 of the industry’s most respected (and divergent) approaches- Tom Barr’s Estimative Index (EI) and Takashi Amano’s Nature-Style/ADA system. While EI focuses on providing nutrients in excess (and resetting through large weekly water changes), ADA focuses on quality growth at a more moderated pace.

APT 3 “Complete” takes a middle path. It is a lot more concentrated than ADA to compensate for the ‘everyday / average / normal’ substrate used by most hobbyists, but less aggressive than EI. You get everything that EI offers- but just more safely / slowly.

APT1 “Zero” allows you to enjoy all the benefits of the ADA approach- unparalleled algae control and the ability to unlock the richest reds in popular plants through nitrate limitation. It should be paired with the use of aquasoil and/or a higher fishload environment.

2. Does APT contain copper?

Yes, in tiny, chelated form.

But isn’t copper harmful?
The amount of copper in APT is so tiny that it is basically harmless. Copper can indeed kill- in the way that the electricity from a 120V AC socket can. But a 1.5V DC battery is quite different.

But isn’t it still copper?
The minuscule amount of copper in APT is in chelated (i.e chemically bonded) form that makes it digestible by plants, but harmless to livestock as it is in a different molecular structure. Chelated copper is also a common food supplement. Think of it as a 1.5V DC battery with an additional rubber casing.

Why have it at all?
Because in the correct structure and trace amounts, copper is both essential and beneficial to plant and livestock health.



1. Should I use APT 3, APT1 or APTe?

APT 3 / Complete should be the default choice. It provides the optimal balance of nutrition and algae control across a wide range of tank styles. It contains a complete set of nutrients necessary for plant growth and does not require additional supplementation.

APT 1/ Zero contains no nitrates and phosphates, and should be used if you have a fish population that produces adequate nitrates in the tank (specifically, If your tank measures >8ppm NO3 by end of the week with no fertilizer dosing and water change).

APT 1/Zero can also be used to induce steep nitrate limitation in tanks, which gives the deepest reds in species such as Rotala rotundifolia and Ludwigia arcuata. This approach is usually paired with a rich substrate to prevent long term stunting due to low nitrogen levels. In this manner, APT 1/Zero can be used as a replacement for the ADA range of liquid fertilizers (Bright K neutral, Green brightly mineral and Green brightly iron).

APT e/ Estimative Index would be your choice if you understand and seek to practice the EI approach to grow plants at a fast speed. EI has the highest risk of runaway algae issues if you have sub-par tank maintenance, sub-optimal CO2 levels or low plant mass.

2. Can I dose APT 1 and/or APT 3, APT e....together?

Yes, it is perfectly fine to do so. For example, after adding more fish, you can switch from using solely APT3 to 'half and half' across APT1 and APT3. 

3. What is the best time of day to dose?

For aquariums with strong lighting and CO2 injection, we recommend dosing around the same time that lights come on. This ensures maximum nutrient availability during photosynthesis. The exact timing does not matter- you can dose slightly before, or after lights come on. 

For aquariums without CO2 injection, growth and absorption rates are 5x-10X slower, so the time of dosing does not matter. Consistency in weekly dosage is far more important.

In general, precision in the timing of dosage is not a major factor in plant health/ growth. Consistency over time matters.  

4. How much to dose?

The default dosing rate for APT Complete/APT Zero is 5ml per 100L, 4 times a week. Alternatively you can dose 3ml per 100L every day. Both routines should be combined with a 30%-50% water change every week.

This dosing rate has been tested to work well for most tanks, however, if you have a very sparsely planted tank or a very densely planted one, you should adjust the dosage based on observations on plant growth.

What about 3 times per week or even less frequently?

For tanks low-light tanks without CO2 injection, dosing once per week is fine.
If you are keeping fast-growing plants under strong lighting, it is better to dose daily or at least 4 times a week. This provides a more consistent level of nutrition in the tank, which matters for fast-growing plants.

5. Are the fertilisers safe for shrimp?

Yes. All APT fertilizers have been tested to be safe even for delicate strains like Crystal red/Caridina shrimps.

6. Will APT fertilizers raise GH?

The magnesium levels in APT fertilizers are too low to affect your tank's GH levels.

APT provides ~1.6ppm of magnesium over the course of a week. In comparison, 1dGH is around 17ppm calcium/magnesium ions.
So you would need to overdose APT by 10X to raise GH by 1dGH.

7. What should I use for a tank that has no CO2 injection?

While APT 1 'Zero' is the default for such a tank, the choice depends heavily on whether you have significant fish load in your tank.

Definitely use APT 1 'Zero' if you have persistently high NO3 levels (>8ppm) and use APT Complete if your tank is densely planted with few fish.

8. How do I switch from an EI style dosing to APT 3 'Complete'?

If your plants were previously grown under the EI regime with its elevated nitrogen levels, a sudden drop to lean levels can cause stunting in some species.

While most will recover in time (about 2-3 weeks); you can avoid this by switching to dosing EI at half-dosage for 2 weeks before switching to APT Complete.

Having a nutrient-rich substrate as a backup also helps.

9. How soon should I start dosing if I have a new tank with aquasoil?

While some brands of aquasoils contain a high amount of nitrogen, they may not contain optimal amount of other nutrients such as potassium or magnesium.
Water soluble nutrients are quickly lost when we change the tank’s water.

Therefore, dosing should be done once there are plants in the tank.

Having good access to all essential nutrients allow plants to adapt faster in new tanks.

10. How do I get a dispenser / pump?

Only 300 Standard Bottles come with attached dispensers. 200ml, 500ml and 1000ml do not. However, all 500ml and 1000ml bottles fit standard "28/410" pumps. "28-410" refers to the bottle's neck size. You can use any off-the-shelf "28-140" pump and it would fit.

11. How do I use APT with an auto-doser?

APT can be used with auto-dosers- many people do so. However, as APT is highly concentrated, crystallization can occur upon evaporation. You can dilute APT with distilled water 1:1 (and double to dosage) to reduce possible crystallization. When diluting, it is important to minimise contamination, as the diluted mixture is more susceptible to mould / fungus. APT can be exposed to room light / some sunlight.


Already using APT?

1. How long does it take to see results?

This largely depends on your light/CO2 levels as these are the main determinants of growth speed in the tank.If fast growing plants have been facing nutrient deficiencies, dosing APT produces dramatically quick effects within days - deeper reds, greener greens and new shoots should be well formed.

In slow growing low tech tanks, the impact can take several weeks, as the rate of change is very slow. The benefit of APT for slower growing non-CO2 tanks is that old growth lasts longer, and stays healthier. Healthier plants are more algae resistant.

2. My leaves are not improving?

As a rule, old leaves do not rejuvenate, as plants channel their energy towards new growth.

This means that a yellowing leaf, or one already damaged with algae, will not become green again, no matter what you provide.

Look out instead for how the new leaves are doing: with good nutrition, they should be richer in colour, be in better form and remain algae-free. For stem plants, you must replant the healthy new portions grown under APT, and discard the old stem and roots after the new portion has grown tall.

3. My leaves are turning yellow?

Slow growers such as Bucephalandra, Anubias, Cryptocoryne species and even Java Fern often take months to show the benefits of improved nutrition. This is because of their naturally slow rates of growth.

In some cases, leaves may yellow after a month after planting because the plant is still adapting to the new tank environment, especially if the plant was grown emersed (only partially submerged) at the farm. This is natural.

Look out for the newest leaves- if they are healthy, you are on the right track. The old leaves may not recover.

For a tank without CO2 injection, new leaves may take several weeks (even months) to form, as the rate of growth is very slow in such conditions.

4. Expiry date?

As a general rule, it is best to use the fertilisers within 24 months of opening.

These are not printed as the inert metallic salts and compounds used have technically indefinite shelf-life when stored properly per listed instructions. 

However, once opened and exposed to the environment, fungi spores and microbes may lead to contamination. 

5. Sedimentation / Crystallisation?

Due to the concentration of the products, sedimentation / crystallisation is normal and may cause the contents to appear cloudy. In some (rare) cases, larger flakes / solids may be present.

They do not affect the efficacy of the product and can be discarded.

6. My plants are not as red as the tanks I see online?

While nutrition plays an important role, pigmentation is dependent on other factors as well.

Light intensity and spectrum are both extremely important. Check out this post for more details.

For picky species, CO2 levels have a big impact. Check out this section on how to improve your CO2 injection.

7. Can I do less frequent water changes?

Yes; doing 30-40% once every 2 weeks will work as well. However, remember that the main aim of water changes is to reduce organic waste levels in the tank and to allow one to do siphoning of detritus. The aim is not the dilution of fertilizer levels.

If you are facing algae issues, skipping this cleaning routine is probably not helpful.

7. Can I change more than 30% of my tank’s water during my regular water change?

If you regularly change more than 30% (say 40%, 50%....), you can still follow the recommended dosage.

Consistency in dosing is far more important. For example, if you regularly change 50%...keep to that. Don't change 10% one week and 60% the next.

Many aquarists do larger water changes because of higher fish load- that is a good approach.

8. What if I’m growing plants that prefer more water hardness?

For planted tanks with plants that prefer slightly higher GH ranges (Rotala sunset, Rotala florida & Downoi), add APT SKY.

9. Should I add even more Iron?

The iron content in the APT formula is more than sufficient. If you are trying to get your plants redder, invest in a better light instead.

Iron only helps to maintain pigmentation. Dosing beyond a certain level does nothing. Our 2Hr Tanks do not receive additional iron other than what is in APT.

It would have been easy to make a fertilizer with much higher iron levels, but we have found that it creates more problems with no visible benefit.

10. I’m still seeing nutrient deficiency in my plants?

Unlike our skin, plant leaves do not heal. So the older leaves will not recover even if the nutrition is now optimal.

The new leaves however should be in general larger and more vibrant. For most stem plants, wait for the new, stronger leaves to develop then consider topping and replanting that portion.

If you are growing picky Eriocaulon species, the primary cause of 'melting' is insufficient CO2.

These are the some of the most CO2 hungry plants in the hobby and require CO2 levels in excess of 35ppm.

11. Using APT 3 / APT E, I measure zero nitrates?

In 2Hr Tanks, we target measurable NO3 (at the end of the day, assuming we dosed at the beginning) of zero. These are biologically mature tanks with high plant mass, and low or moderate fishload (which can be tricky to define, as feeding can affect bioload even more then livestock population).

APT was designed to provide this more moderated N level, which gives 2 benefits:
1. Richer color from Nitrate Limitation.
2. Algae Control- less 'free' N= less food for algae, basically.

Nitrates generally measure zero because of plant absorption, which take place continually.
For example, a standard daily dose of APT3 adds less than 1.5 ppm of NO3, and most well planted, mature tanks with moderate fishload easily digest that amount every day.
So when we measure NO3 at the end of day, it reads zero.
(This can be shocking to EI users!) These tanks all measure zero for example.

So for mature, planted tanks with NO3 that measure above say 5ppm at the end of a normal day, we almost always advise users to switch to APT 1.
We also suggest they review feeding, and finally bioload. We try to aim for close to 0, or 1 or 2ppm residual NO3 readings.

Of course, for new tanks with a yet-to-mature filter, low plant mass etc, nitrate readings can be high.
So as a rule, we tell users to use APT 1 for the first 3 months. Measurable nitrates would come from fish food/ waste, and it is good to tune feeding etc that way.

The low N target is really helpful for the kind of tanks we focus on: strong light, fast-growing, colorful plants.

12. My carpet has uneven growth?

With more optimal nutrition, the newer leaves tend to be larger and more vibrant. The older leaves last longer as well. In carpets, this can create a sense of unevenness- big fat new leaves mixed with sad-looking older ones. This is natural, as plant leaves, unlike our skin, do not heal. So the older leaves will never become similar to the new ones.

The best way is to remove the old growth completely, and replant the new leaves, taking care to spread them out rather than planting them all together in a bunch. Most beginners plant in big clumps.

Experienced aquarists plant in tiny, well-spaced out bunches to give room for the carpet to grow evenly.

13. Content Labels

On some bottles, the contents of APT are listed in percentages.
On others, in ppm. They look very different?

Per fertiliser regulations, newer APT labels show content in percentages (e.g 0.7% Total Nitrogen)
Older labels list certain compounds in ppm (e.g. 5ml per 100L adds 1.8ppm NO3 )

They look different because they are stating different things.

1.8ppm of NO3 refers to a specific compound (NO3), and at the specific concentration of 5ml per 100L.
0.7% Total Nitrogen refers to the nitrogen element only (in the bottle) and calculated per regulatory requirements on how 'Total Nitrogen' is defined (in the same way that the food industry has continually evolving regulations that determine how, say, 'protein' is defined)

In summary:

  • The old 'ppm' labels represented the contents in hobbyist vernacular. Newer labels reflect current fertiliser regulations.
  • APT's unique Capstone Formula has remained consistent, with subtle improvements year after year.