Your Cart is Empty

How to stabilize a new planted tank

February 18, 2024 11 min read

How to stabilize a new planted tank

The tank above was grown in in less than 6 weeks, in a tank that was not pre-cycled. This guide explains on how to smoothen out the maturation process for folks that are in a rush to finish their planted tank projects and do not have time to let their tanks mature normally.

What makes new planted tanks so unstable?

New tanks that are not yet biologically matured present a volatile environment for inhabitants. Ammonia that is unprocessed and free floating pathogenic bacteria feeding off detritus causes stress to both livestock and plants - this is one of the causes of melting plants in a new tank. New aquasoil often release ammonia and other volatile organic matter as the soil transits from terrestrial to submerged state. This state change also entails large changes in the microbial environment as microbes more suited to the submerged environment develop and supersede microbes that existed in the previously terrestrial environment.

All these environmental stresses cause more delicate plants to melt - tissue culture plants and exotic species, or weak plant samples are especially vulnerable. Sensitive livestock such as Caridina shrimp will also fare poorly in immatured tanks.

The processes for biological maturation in the tank all play out at the microbial level that is invisible to human eyes, but we can see whether they have played out by testing and observing what is happening in the tank. As the microbial community in the tank matures, ammonia cycling completes and bacteria bio-film binds the fine particles in the water column, producing crystal clear water. Beneficial microbes consumes algae and other pathogenic bacteria.

One way to get the biological system in place without risking plants is by doing a dark start - running the tank with substrate and filter in place, but without plants or lights for a couple of weeks. However, many aquarists do not have the patience or time to do a dark start.

In this guide we describe steps to speed up the process and mitigate the harsh starting conditions of a newly setup planted tank so that plants can skip the melting and adaptation phase and get into the growth phase quickly.

Diatoms, dull plants that are attacked by algae and deteriorating growth are all common symptoms in a newly planted tank. With the steps below, we can minimize or even skip most of the downsides, while accelerating the maturation process. To see how we managed the tank above, see our link on Solving algae issues without algicides.

Main goals in the first few weeks of a new planted tank

  • Accelerate microbial propagation, and thus maturation of the tank
  • Accelerate ammonia cycling
  • Remove excess ammonia and organic waste
  • Reduce free floating particulate matter and algae spores
  • Reduce pathogenic microbes that cause plant melt and livestock stress
  • Ensure that plants have enough nutrients and CO2 to acclimatize fast

Creating an ideal environment for microbial growth

At the heart of accelerating a tank's maturation is creating a conducive environment for beneficial microbes - principally, the microbes that are responsible for ammonia cycling, consumption of algae and pathogenic bacteria. These microbes tend to favor aerobic conditions. For ammonia cycling bacteria, having organic carbon, phosphates and magnesium available will speed up their propagation rates. Ensuring good gaseous exchange and oxygen levels in the tank is very important. Even for a tank with many aquatic plants, plants only produce oxygen during the light window of the day, which could be less than 1/3 of the day depending on the tank setup. Microbial action runs 24/7 and having good oxygen levels throughout the day is ideal. 

1. Seeding the tank with starter bacteria/microbes.

Use a matured filter or mix a portion of substrate from a previous setup in the new setup to seed the tank with microbes. Using a portion of matured filter media in a new filter setup also helps. Adding commercial bacteria strains can also speed up the process.

2.  Having good oxygen levels through having a clean water surface.

Make sure your water surface does not get clogged with an oily film. Using a surface skimmer ensures that the water surface is always clear. Surface skimmer filter intakes are especially good because they take in organic waste that gather at the water surface and feed it directly into the filter with oxygen rich water.

3. Having good oxygen levels through having a good flow pattern.

Gaseous exchange only occurs at the water surface - being able to circulate oxygen rich surface water with water layers deeper in the tank is important. Make sure the flow pattern in your tank exchanges the surface layer of water in the tank with water deeper down in the tank.

4. Aim for filter turnover between 6x and 10x.

For most tanks, having a filter of at least 6x the tank size is ideal. This means that for a 100 litre tank, you will want a filter that runs at a flow rate of least 600 litres per hours.

5. Plant densely from the start.

Plants stabilize the system by absorbing ammonia, heavy metals and by providing a favourable home for microbial life. Aim to have at least 50% of the tank substrate surface area planted. Adding adequate nutrients/CO2/light from the start for plants to adapt well to the new environment is important.

A good flow pattern brings oxygen rich surface water to deeper water layers in the tank. A stronger flow brings debris and organic waste particles to the filter to be digested.

Using a surface skimmer intake for the filter keeps a surface film from forming and feeds oxygen rich surface water directly into the filter. Waste proteins accumulate on the water surface are drawn directly into the filter to be digested.

Having a clean water surface, and a slight ripple across the surface layer of the tank gives good oxygen levels without needing the usage of air stones.

Aged filter media looks yucky but contains useful beneficial microbes. Mixing aged and new filter media is a good way to kick start your microbial community without spending money on expensive commercial additives. Squeezing the detritus from old sponge filters into your tank or filter will also work.

Removal of organic detritus, excess ammonia, pathogenic bacteria, algae spores

For aquasoil and soil based substrates, a lot of volatile organic matter can be released at initial submergence of the soil. For ammonia rich aquasoils, a high level of ammonia can be released. ADA aquasoil for example, can release 10+ppm of ammonia within the first few days of submergence. This makes large, regular water changes necessary for the first couple of weeks if a dark start was not used when starting the tank. Even for tanks where less volatile substrates are used (for example, inert sand), large water changes are useful for removing potential algae pores and organic detritus from acclimatizing plants that shed their old leaves. This prevents algae from blooming out of control and smothering plants during the initial few weeks.

1. Large water changes during the initial weeks.

For tanks using aquasoil, we recommend changing water (60-80%) once every 2 days for the first couple of weeks, then once every 5 days for the next couple of weeks after that. After the tank has stabilized, a water change schedule of once every week should be adequate.

2. Siphon away detritus on the substrate surface during water changes.

Algae spores and organic detritus gather on the substrate surface. Siphoning away surface debris by water changing the 2hr Way removes detritus and minimizes algae blooms in a new tank. Having a clean tank environment reduces melting in newly introduced sensitive plant species.

3. Cutting away badly deteriorating old growth on acclimatizing plants.

As newly introduced plants acclimatize to the tank environment, they will produce new leaves that are optimized for the new environment. At the same time, they may shed older leaves and channel the energy into new growth instead. As the plants stop defending old growth, old growth attracts algae. Allowing the plant to refresh itself by cutting away old growth and making space for new leaves reduces algae significantly in the tank.

4. Removing minor algae blooms manually during water changes.

Diatoms, green dust algae and BGA are common in new tank setups. Rather than using harsh algicides at this early stage of the tank, minor algae clumps should be siphoned away during water changes so that they do not smother plant growth. We have more details on this in this guide on controlling algae without algicides.

Deteriorating old leaves are an algae magnet. These can be removed as the plant replaces them with fresh new leaves that are resistant to algae.

Trimming off old growth reduces over-crowding and gives space for new algae free growth. 

Ensure plant growth parameters are in place

Deteriorating plants contribute to organic waste levels and are a prime target for algae. Having good growth parameters is essential for plants to adapt to the new tank conditions quickly and having a large healthy growing plant mass is the fastest way to stabilize a new tank.

1. Aim for high CO2 levels (if injecting CO2)

Having high CO2 levels greatly accelerates aquatic plant growth and adaptation. Newly introduced plants which may have been grown emersed have to adapt to extracting CO2 out of the water column upon submergence. The biological machinery to extract CO2 is energy intensive and having ample CO2 available will speed up acclimatization significantly. 

2. Dose a comprehensive water column fertilizer.

Many aquarists avoid fertilizing their newly planted tanks as newly submerged aquasoil is nutrient rich. However, newly introduced plants will not have developed root systems yet and have limited ability to draw nutrients from the substrate. These plants will use their internal energy stores as well as draw nutrients through the water column, thus having all essential nutrients in the water column allows plants to acclimatize faster.

Fresh aquasoil often release ammonia, which can provide nitrogen for plants. However, nitrogen is not the only nutrient that plants need to grow. Many of the other nutrients required such as Magnesium or Potassium are not emitted into the water column significantly by aquasoil - they may be contained within the soil matrix but the plant needs to have an established root system in order to access it. Dosing a comprehensive fertilizer into the water column is thus very helpful to newly introduced plants.

Signs of tank maturity and stabilization

When newly introduced plants acclimatize to being planted in a tank, they tend to channel their energy into producing new leaves that are adapted to the new environment. New leaves that are well formed and healthy produce defensive chemicals at the molecular level that deters algae from attaching to them and also prevents damage from microbial decomposers. Observing new leaves that are large, well formed with good coloration and clean of algae is a sign that the plant is adapting well. Old leaves are abandoned and the plants stop defending them from both microbes and algae.

Deterioration of older leaves is an expected symptom in newly introduced plants. These leaves can be cut off to make space for new growth. For stem plants, the healthy top portion can be replanted, and the damaged bottom portions uprooted and discarded. There are many signs that tank stability is moving in a positive direction:

1. Signs of healthy new growth.

Plants produce new growth adapted to the new tank conditions. If the plant has successfully acclimatized, new leaves should be very algae resistant even if the older leaves are attacked by algae. You can then trim off older leaves to give space for new algae free growth. Over time, the entire tank of fresh new growth will be very resilient against algae.

2. Cloudy water turning crystal clear.

Matured biological systems have plenty of bacteria bio-films that bind fine particulate matter down and keep the water crystal clear. Beneficial microbes keep pathogenic bacteria down, creating a healthier environment for livestock.

3. Ammonia cycling complete.

Ammonia readings would diminish to zero as the tank completes its cycle. In lower pH tanks, this could take a couple of months.

4. Reduction of algae.

As the tank matures, there should be reduced incidence of algae - diatoms and green dust algae which are more common in fresh planted setups should disappear on their own as plant growth accelerates. Plant growth out complete algae over time, and microbes that are micro herbivores also reduce algae in the tank.

What if the tank fails to stabilize?

Tanks generally start to stabilize fast when plants acclimatize to the new tank environment and start growing fresh new algae free growth. However, there are many variables that may set back the process such as a lack of equipment, poor tap water quality, weak initial plant samples, poor substrate choices and more. On the other pages on this site, we describe how to optimize each element, however, due to limitations of each hobbyist due to regional or budgetary reasons, switching out tank equipment or other essential parts of the system may not be feasible. In the hobby often we have to make the best of what we have. These are the few steps you can take if the system cannot stabilize itself with the steps above.

1. Patience. How long to wait?

Tanks can take much longer to settle in sometimes. Having a misstep that crashes the system or a spike in plant stress can retard plant growth for weeks. Plants will also take longer to adapt in cases where tap water quality is questionable or other growth parameters are not in place due to equipment restrictions. Give the tank some time - low tech (non-CO2 injected tanks) can take a few months to stabilize and start growing well. A low tech tank should not take more than 6 months to stabilize. For a CO2 injected tank, taking more than 3 months could be a sign that there are more serious fundamental problems with the setup used (or that it is a poorly optimized setup).

2. Changing out plant selection.

Plant species selection has a huge impact on tank outcomes. Plant species vary greatly in their demands. Switching out difficult/picky species for easier plants is one way to move forward with a difficult tank. Sometimes shifting a difficult plant's position in the tank to a more optimal spot can also work for borderline cases. 

3. Tune down the light. At least for the short run.

Algae is the largest problem for most tank setups that fail to stabilize. Tuning down the light can help mitigate algae issues significantly. The light can be tuned back up after the tank has stabilized. This is a significant factor often ignored by most folks as light levels in the tank are difficult to measure without more specialized tools.

All aquatic carpets can be grown with 40-50umols of PAR at substrate, as long as CO2 is ample. Most green plants will also grow well at this level, though higher light can give more compact growth. Red plants will start getting good coloration around 100 umols of PAR. Even the most demanding species can start growing between 100-150 umols of PAR. While some species will develop better coloration and density with higher light levels, we can start tanks at lower light levels to allow stability to set in first. This is especially so for tanks that do not have demanding plants that require a lot of light.

Lower light levels make it much easier to manage algae. However, PAR meters are expensive and most hobbyists will have to guess the PAR levels for their tanks.


With the steps above, tanks at the 2hr Aquarist gallery can be brought to a good level of maturity in about 6 to 8 weeks. The pictures taken above and below show the difference after 45 days from first planting. The more delicate species such as Hygrophila chai and Eriocaulon species were only added after the first 2 weeks has passed. 

There are many other factors that may confound the hobbyist's journey that may be hard to control for, such as tap water quality, or the quality of freshly introduced plants. However, having good maintenance and good tank cleanliness maximizes chances of success even when other factors are not optimal.

To learn more about tank cycling and related articles, click here.

To learn more about gaseous exchange, click here.