fertilising planted aquariums

There are many different brands, types and methods of fertilising planted aquariums and it can be a daunting task figuring out what will work best for your particular setup. It’s a question we often get asked in store. That’s where this guide will hopefully help you make the right choice to make sure you can maintain a healthy and amazing looking planted aquarium.

Planted Tank basics

The key considerations to keep in mind if you want to encourage and maintain vibrant & healthy plant growth.

Pick the right plants !

Whenever you buy plants make sure you check their requirements – ask the store, research and then purchase.

How to plant your plants

Some plants need to be rooted in a substrate. Some plants float. Some plants can be attached to wood or rock. some will grow tall, some small. Some plants cannot be grown underwater! Make sure your placement is right for each plant

Choosing the right equipment

Using the right light, temperatures, filtration and substrate are just as important as what fertiliser you use. An unsuitable light for example will not provide good growth. different temperatures will call for different types of plants.

Stocking suitable fish

Make sure you know the requirements of which fish you want to, or are keeping. Can they be kept with plants? Will they benefit from a planted aquarium? Will they eat plants? Will a clean up crew be possible?

Test your parameters

Test your tap water as well as your aquarium water. Bare minimum it’s recommended to test for pH Ammonia, Nitrites and Nitrates. Phosphates, kH and gH are also helpful to test for.

Consult a deficiency chart

I’ve attached a very helpful nutrient deficiency chart provided by Seachem to this guide. This can be incredibly useful in some circumstances if you can narrow down what problems you are facing.

We’re always more than happy to help you diagnose and address problems in your aquarium so don’t be afraid to ask!

Making sure your setup will suceed

Using the correct type of lighting

‘Low Tech’ setups will nearly always use lower intensity lighting to help prevent excess algae growth and to accommodate easy to care for plants.

‘High Tech’ setups contrarily will usually employ high intensity lighting to help encourage vivid colours of certain plants such as red leaved plants (alternanthera) and to encourage dense growth.

It’s important, regardless of what type of setup you choose, to make sure your light can provide the correct type of light (PAR - light that plants can use) and most importantly for the right duration (photoperiod).

Maintaining appropriate circulation

It’s not always essential to provide strong circulation, and you should research what flow rates are recommended for your size aquarium, fish and plants, however, some groups of plants such as carpeting species will benefit from strong circulation (A turnover of roughly 8 - 10 times an hour can be beneficial).

Floating plants and those that grow on the surface (Nymphoides) may be damaged by strong water flows near the surface, so positioning of the outflow is critical.

If your filtration is not sufficient to provide amble circulation then you can always add a secondary filter, upgrade or even use a circulation pump.

Providing the best base for plants

The vast majority of aquatic plants will benefit from a specialised planting media. There are several reasons for this but the main benefits are that they allow healthy root growth, can store & release nutrients and they can act as an active bed for a beneficial bacteria colony. 

Most types of sand and gravel are inert (will not alter water chemistry) and are not porous. This means that they cannot store nutrients. Gravel and sand can be used in a planted tank but it’s important to pick the best plants for this and to address the lack of nutrients, whether this be by using root tabs underneath the roots, or by addressing nutrient needs solely through liquid fertiliser.

Also keep in mind some plants prefer to be attached to wood or rock! (Java fern, Anubias, Bucephalandra etc.)

is there enough carbon dioxide for my plants?

This is quite often the deal breaker when it comes to what plants you can and cannot grow. Carbon dioxide is an essential nutrient to basic plant metabolism, and should be the first thing you check for if you see signs of deficiencies in your plants.

In terrestrial plants (plants grown on land) CO2 can be taken directly from the air surrounding them. In aquatic environments however, CO2 intake is limited to how much CO2 the water surrounding the plants has dissolved. ‘Easy’ plants or low demanding plants are those plants that have low CO2 demands or plants that can derive a source of carbon from the water column.

For the majority of aquarists, the easiest way to add carbon dioxide is to either inject gaseous CO2 and dissolve it into the water column, or to use a liquid carbon source. CO2 injection is by far the most efficient choice for most aquariums, but liquid supplementation is always an option if the cost of CO2 kits are out of your budget. As with fertilising, there is a lot to consider with using CO2 and we’re always happy to help answer any questions and guide you along the way.

Now to the main topic of this guide, Fertiliser

In this guide I’m going to be talking a lot about different nutrients needed by plants and, well quite frankly, it is not the simplest of topics. I STRONGLY recommend that anyone reading this does their own research and uses any information here as a guide only. I would also strongly suggest that if you think you need to add any supplements to your fertilising regime, you test your water parameters (if possible) to see if you have adequate levels, and to consult deficiency charts to get a rough idea of what might be the cause.

Comprehensive & Basic Fertilisers.

When we talk about comprehensive fertiliser, we are referring to a fertiliser that includes several needed nutrients, and a product that could be called a ‘complete’ fertiliser. To call a fertiliser a complete fertiliser does NOT necessarily mean you do not need to add other nutrients. It would be impossible to create ONE and only ONE fertiliser for all setups, as there will always be different circumstances to consider.

In some cases, you may not need to add any more nutrients, or you might not even need to add nutrients at all if your using a nutrient rich substrate (always check to see for how long each substrate will release nutrients). The best way to work with these products is to use them as a foundation to work from.

Extra supplementation

Iron (Fe)

This is one of the most common fertiliser picked off the shelf after comprehensive fertilisers. In the case of low tech setups, the iron contained within the comprehensive fertiliser might be enough.

In a higher tech setup or a setup with quick growing plants, iron can be depleted quickly. Iron is essential for production of chlorophyll (what provides the green pigment to leaves) as well as growth and basic metabolic processes.

Note: - Red plants will not get any 'Redder' from putting more iron fertiliser in unless they are deficient. In order to achieve deeper and more vibrant reds you may want to instead look at lowering nitrate levels and increasing light intensity.

Nitrogen, Potassium & Phosphorus (NPK)

The dread I see in customers faces when I suggest adding some of these nutrients to their aquariums goes to show how controversial their use is seen to be. These three nutrients are ‘Macro Nutrients’, meaning they are essential for plant growth and metabolism in higher quantities than any other (not including Hydrogen, Oxygen and Carbon).

Nitrogen & Phosphates – to dose, or not?

Sources of nitrogen and phosphorus will often be present in aquarium water from organic waste i.e. fish food, fish waste, decaying plant matter and even the water source you use. Not every aquarium will need supplementation of these two nutrients, although deficiency in these two is more common than many people think. It’s important to test your levels in these two (Nitrogen content is best tested via Nitrate and Ammonia/Ammonium tests) as well as consulting a deficiency chart to determine if your levels are low.  High levels of either of these two nutrients may result in algae growth in the best-case scenario and fish fatalities in the worst, so make sure you monitor your parameters!


When customers come to the shop with signs of deficiency, this is one of the top contenders. Potassium is quite often lacking in aquariums. Many Comprehensive fertilisers will contain a source of potassium as it is unlikely to cause algae problems. Having said that, in high tech tanks or setups with lots of plants this is often not enough.

Liquid Carbon

As mentioned previously, a source of carbon can be added to aquariums via liquid supplementation. There is often much confusion as to how you can add ‘liquid CO2’ to your aquarium, as surely CO2 can’t stay dissolved in a liquid for however long a treatment is on the shelf? Liquid carbon fertilisers are NOT dissolved CO2! They are instead a source of carbon that can be used by plants. Without going into a painful complicated biochemistry lesson, the source of carbon (most) products use is very similar to a carbohydrate that plants utilise in the processes of using CO2. So in essence, it’s a shortcut in the process that can bypass the (sometimes) need for dissolved CO2.

Surely theres not more?

It’s perfectly possible to maintain a healthy planted tank with a fraction of what’s been mentioned here, but to continue with the theme of this guide, it all depends on your setup!

High density/High tech/fast growing setups will quite often need higher concentrations of trace elements to maintain peak health. Trace elements can be quite often depleted very quickly after dosing.

Growth boosters

Seachem advance is a misunderstood and underrated supplement. Designed to be used on top of any fertiliser schedule, it acts to increase root production, nutrient absorption and eventually increase growth. It is comprised of ‘Phytohormones’ (think steroids for plants) and it’s main purpose is to help plants utilise the nutrients provided more efficiently. Want proof? The 5ft planted aquarium instore had a course of Seachem advance for the first three months and the growth far exceeded expectations (mine included), especially with some of the more delicate stem plants.

Buffers & Minerals– do I need to use them?

A tricky question and, well it depends! If you’re reading this guide in an area with similar water parameters to our shop (high pH, kH & gH) then the majority of the time you will not need to add any more mineral content to increase these levels (unless you are trying to reach a set goal). You may however want to look at ways to decrease your parameters. To generalise, most plants will prefer a more neutral or even soft setup and so using buffers to decrease kH (carbonate hardness) will help not only lower pH, but some will also provide available sources of CO2 (acid buffers).

Another case where you will need to use buffers and minerals is if you use RO or very soft water. It’s important to remember fish and plants do need some mineral content, and every species will have an optimum general hardness (gH) and carbonate hardness (kH). If you are using solely RO water then you will need to add buffers to increase these parameters.


There are many different types of planted aquarium setups, and each setup may differ in nutrient requirements. Research what setup you want to create, what plants you want to grow, what fish you want to keep. And don’t forget, you can always ask a member of staff instore for information on any of the products mentioned here. We’re more than happy and advise on products, plants and livestock.

Our 5ft planted aquarium