Planted tanks can bring beauty to any room and provide a more natural home for your fish. If you’ve ever tried to grow underwater plants, you likely know how challenging it can be to keep them alive, let alone healthy and vibrant. Using the best aquarium plant fertilizer can help you create the most beautiful planted tank. Think of your fertilizer like plant food. Our favorite aquarium plant fertilizer is the SeaChem Flourish Freshwater Plant Supplement.
Plant fertilizers can help maintain a beautiful and thriving aquatic plant community, but not all of them are safe for your other tank inhabitants such as your aquarium fish and shrimp. We’ve tested many different fertilizers and put together these reviews to help you choose the best one for your tank.
Best Aquarium Plant Fertilizer Options:
What Is the Best Aquarium Plant Fertilizer?
Our overall favorite aquatic plant fertilizer is the SeaChem Flourish Freshwater Plant Supplement. It provides all of the nutrients your aquarium plants need to grow and thrive, and it’s safe for your fish, aquatic invertebrates, and healthy tank bacteria.
Do Aquatic Plants Really Need Fertilizers?
Most aquarists understand that aquatic plants need carbon dioxide and light to grow, but many don’t know that a myriad of macro and micronutrients are also required. Aquarium plants need nitrogen, phosphorous, and potassium in relatively large quantities, along with many other nutrients in less significant volumes.
Your tank plants may be able to grow to some extent in unconditioned tank water. However, most require some type of fertilizer to thrive and produce that naturally vibrant and healthy look planted tank owners strive to achieve. Even hardier plant species, like an Amazon Sword, Anubias, or Java Fern, will appreciate a little fertilizer every now and then. If you have fast-growing non-aquatic plants like pothos in your tank, they can overpower your aquatic plants and make fertilizer a good idea.
A good fertilizer will provide your aquatic plants with everything they need to maintain healthy growth while remaining safe for fish and their tankmates.
How to Choose an Aquarium Plant Fertilizer
There are several things you should consider when choosing a fertilizer to add to your planted tank.
The most important aspect of an aquarium plant fertilizer is its nutrient content, as this will determine how effective it is at keeping your plants healthy. Not all nutrients are equally important, and aquarists generally break them down into two categories based on how much of each is necessary for plant health: macronutrients and micronutrients. It is important to make sure your plants get the correct essential nutrient profile for their health.
Macro Versus Micronutrients
Macronutrients are those that your aquatic plants need in large quantities to thrive. Aside from sunlight and CO2, macronutrients are the most essential things your planted tank needs to grow.
Micronutrients are those that your plants need in far smaller quantities. Many of the micronutrients aquatic plants use are found naturally in tap water, so you may not need to add them to your tank at all. However, you’ll need to add others for the best growth environment possible.
Nitrogen is the most critical macronutrient for your tank plants. Plants can get some nitrogen naturally from fish waste and leftover food once your tank bacteria break them down to nitrates. However, aquatic plants need an abundance of nitrate, and levels in your aquarium likely won’t be sufficient without supplementation.
Phosphate is crucial for all plants, including aquatic ones. This nutrient is used for photosynthesis and energy storage, so it’s directly responsible for plant health and longevity.
Your aquatic plants use the final macronutrient, potassium, to aid in the transportation of water and food. Potassium helps maintain healthy-looking plants and vibrant leaves.
Your aquarium plants need an array of other nutrients in far less significant quantities for healthy growth. These include iron, zinc, copper, boron, manganese, molybdenum, sulfate, chloride, calcium, and magnesium.
Many of these micronutrients are naturally present in your tap water as ions, so while supplementation doesn’t hurt your plants, it may not be totally necessary in some cases.
The specific amounts of each nutrient your live plants need will depend on many different factors. Heavily planted tanks require far more nutrients, as do rapidly-growing plants, like Waterweed and Hornwort. The size of your plants, number of other tank inhabitants, and natural water quality can all affect how much of each nutrient your plants need. As such, it’s not possible to identify exact amounts without rigorous testing.
How Do Your Plants Take In Nutrients?
Aquatic plants generally use two different methods of nutrient absorption – roots or water column absorption. The absorption method of your plants can help determine what type of fertilizer you need.
Some plants like Echinodorus and Cryptocoryne take in nutrients through their root systems, much like terrestrial plants. It’s best to use slow-release tablets in your substrate for these plant types, as liquid options won’t provide adequate nutrients to their roots.
Other aquarium plants like green pennywort, java ferns, and Anubia only absorb nutrients through their leaves. Slow-release tablets are far less effective for these plant species, so a liquid fertilizer is better for them.
Types of Aquarium Plant Fertilizer
There are three primary types of plant fertilizers, each of which is ideal for different setups and plant species.
1. Liquid Plant Fertilizer
Liquid plant fertilizer is a liquid formula that requires you to add the desired quantities for your tank size directly to your water. Application is the most straightforward, but it’s easiest to over-treat your water with this type of fertilizer.
Liquid formulas are best for plant species that absorb nutrients through their leaves, as it gives them the most straightforward access to the nutrients they require.
2. Pre-Packed Substrates
Pre-packed substrates contain the nutrients required for healthy plant growth within the substrate itself. The application of nutrients is very straightforward, and the substrate controls the release rate to ensure that they get dispersed evenly.
The major downside of pre-packed substrates is that you can’t control the amount of the nutrients added to your tank without restricting substrate or adding more. This may put limitations on how your tank is set up.
Additionally, the nutrient-rich substrate will need to be replaced over time rather than cleaned like some other substrates. As such, the cost in the long run can be higher.
Pre-packed substrates are best for plants that absorb nutrients through their roots.
3. Aquarium Fertilizer Root Tabs
Fertilizer root tabs are small tabs that you place under or within the substrate in your tank. They offer an excellent way to customize how much of the necessary nutrients are available in your substrate, unlike pre-packed options. These are clearly for your rooted plants.
Root tabs are relatively easy to use, but they’re not quite as convenient as liquid fertilizers. They allow you to use any substrate you like, and you won’t need to replace it as often as you would with pre-packed substrates.
As the name suggests, fertilizer root tabs are best for aquatic plants that absorb nutrients via their roots, as they deposit nutrients into your substrate for use.
Advantages of Using Aquarium Plant Fertilizer
Aquarium plant fertilizers offer many different benefits to your planted tanks. Below are the most compelling reasons to use a good plant fertilizer in your aquarium.
Help Maintain Plant Health
Of course, the number one reason to use an aquarium plant fertilizer is that it keeps your plants healthy and helps them live longer. The nutrients in fertilizers aid in oxygen absorption, photosynthesis, energy storage, and water and food distribution through your plants. All of these benefits translate to healthier plants that will live longer and be able to stand up to disease and other common problems.
Boost Plant Growth
Plants require the macronutrients and many of the micronutrients we mentioned previously in order to grow. When you first plant in your tank, you’ll want the specimens to take root and grow into the space you’ve allotted for them. The nutrients in aquarium plant fertilizers promote and are necessary for growth.
Improve Tank Appearance
The nutrients in fertilizers stimulate chlorophyll production, which means your tank’s plants will look greener and more robust. Healthier plants are a huge benefit for a planted tank, and the improvement to your setup’s natural beauty is a nice bonus!
Healthy For Fish and Other Tank Inhabitants
Healthy, thriving plants produce more oxygen and consume more nitrates – which are poisonous to fish and naturally occurring in all tanks – than dying or sickly plants. More oxygen and more efficient scrubbing of harmful compounds ultimately mean your fish, invertebrates, and tank bacteria all benefit.
Best Liquid Plant Fertilizers for Aquariums
After testing many different liquid formulas in a variety of planted tanks, we’ve narrowed down the options and decided on what we believe are the best liquid fertilizers available. The following are our top picks, and we’ll include more in-depth reviews below:
- Seachem Flourish Freshwater Plant Supplement
- Seachem Flourish Potassium 500ml
- Seachem Flourish Phosphorus 500ml
- Seachem Flourish Nitrogen 500ml
- API Leaf Zone
1. SeaChem Flourish Freshwater Plant Supplement
This liquid fertilizer contains an abundance of micronutrients as well as some macronutrients that will help your plant thrive. You will need to supplement this with more macronutrients, which SeaChem sells separately.
The metals required by your aquatic plants aren’t chelated, which means they’ll fall out of suspension if they sit too long. This makes it harder to over-dose your tank, but you will need to add to your water daily or every other day. Despite the frequent dosing requirement, it’s very affordable.
This formula is entirely safe for fish, invertebrates, and all other organisms in your aquarium.
- It has non-chelated metals to maintain tank safety
- The formula boosts disease resistance for your plants
- It includes an abundance of nutrients required by your plants
- It’s harder to over-dose your tank than with other liquid fertilizers
- It’s safe for fish and all other organisms
- You’ll need to supplement this with other macronutrient fertilizers
- You’ll need to dose your water at least every other day
- It contains fewer macronutrients than many other formulas
2. SeaChem Flourish Potassium 500ml
This fertilizer from SeaChem contains only potassium, which means it lacks nitrogen, phosphate, and all of the micronutrients your plants need. You’ll need to supplement this with other products, but this is very helpful for treating potassium deficiency in your tank without throwing the other nutrients out of balance.
Provided you use this formula as directed and monitor your potassium levels, this is completely safe for fish, invertebrates, and healthy tank bacteria.
This fertilizer is very affordable, even when you combine it with the other supplements you’ll need for healthy aquatic plants.
- It allows you to treat potassium deficiency, specifically
- It helps keep leaves full and healthy
- It’s safe for fish and other tank inhabitants
- It’s affordable
- It doesn’t contain all of the nutrients you need for healthy plant growth
- It requires more water testing than an all-in-one formula
3. SeaChem Flourish Phosphorus 500ml
This formula from SeaChem contains only phosphorus, which means you’ll have to purchase other supplements to provide your plants with nitrogen, potassium, and the array of necessary micronutrients for the best results.
This formula allows you to treat phosphorus deficiency in your aquatic plants without disturbing the levels of the other nutrients in your water. As long as you use it as directed, it’s completely safe for all of the organisms in your tank.
This liquid fertilizer is very affordable, so you’ll be able to purchase this along with the other necessary supplements without spending too much.
- It allows you to treat phosphorus problems without disturbing other nutrient levels
- It improves plant life and longevity
- It’s safe to use in tanks with fish and invertebrates
- It’s very affordable
- It contains only a small portion of what your plants need to thrive
- You’ll have to test your water frequently when using it to monitor levels
4. SeaChem Flourish Nitrogen 500ml
This liquid fertilizer contains only nitrogen. In most cases, you’ll also need to purchase supplements that include phosphorus, potassium, and all of the required micronutrients to maintain plant health and boost growth.
The benefit of a standalone nutrient like this is that you can fine-tune your nitrogen levels without having to worry about creating imbalances in other nutrients as you would with an all-in-one formula.
This fertilizer is very affordable and is likely to fall within your budget, even when you consider that you’ll need to make additional purchases.
- It provides an easy way to treat nitrogen deficiency
- It improves plant coloration and boosts growth
- It’s safe to use in any tank, as long as you follow dosing directions
- It’s affordable
- It will require you to purchase additional supplements
- Frequent water testing is necessary to get correct nitrogen levels
5. API Leaf Zone
This formula contains potassium for more vibrant, healthy plant leaves, as well as chelated iron to keep leaves green and promote growth. This doesn’t include the other macronutrients or micronutrients your plants require, so you’ll need to purchase additional supplements.
The combination of nutrients means you won’t be able to treat deficiency of one without also raising levels of the other. This likely won’t be an issue for most tanks, but it gives you less control than single-nutrient fertilizers.
This option is very affordable. Even when you combine it with other necessary supplements, it’s likely to fall within your budget.
- It boosts plant growth
- The formula promotes green, healthy-looking leaves
- It’s safe for all tank inhabitants if used as directed
- It’s very affordable
- It doesn’t require all of the nutrients your plants need
- It gives you less control over nutrient levels than single-ingredient options
Pre-Packed Substrate Aquarium Plant Fertilizer
If you’re looking for a more straightforward – and sometimes safer – dosing method than a liquid fertilizer, we recommend the below pre-packed substrates for your tank.
1. UP AQUA Sand for Aquatic Plants
This pre-packed substrate is formulated to maintain a very steady pH level, which improves nutrient uptake in your plants. It does lower the water pH slightly, so keep that in mind when purchasing.
This substrate includes all of the nutrients required for plant growth and health, but you may need to supplement as time goes on and the nutrients get used. We found that this lasts for about a year before a noticeable decline in nutrients.
It doesn’t produce cloudiness in your tank, and it’s safe for use in aquariums with fish and invertebrates.
- Includes all of the nutrients you’ll need for plant health
- The slow-release substrate controls nutrient levels wonderfully
- It helps control water pH once stabilized
- It doesn’t make your water cloudy
- It lasts for quite a long time with little maintenance
- It’s only available in black
- It lowers your tank pH a bit
Aquarium Root Tab Plant Fertilizer
Root tab plant fertilizers offer a convenient way to add nutrients to your tank while limiting the risk of overdosing. Below are our favorite root tab fertilizers for use in planted tanks.
SeaChem Flourish Tabs Growth Supplement
These root tabs include all of the nutrients your plants require, including nitrogen, potassium, phosphorus, and an array of micronutrients. You may need to supplement with a liquid formula if you run into issues, but these tabs are all you need in most cases.
They’re easy to use and control the release of nutrients into your water to help maintain healthy levels, so you won’t need to worry about overdosing.
These are only suitable for plants that uptake nutrients from their roots. They’re safe for fish and invertebrates, as well as healthy tank bacteria.
- The slow-release design helps limit over-dosing
- Their under-substrate placement is ideal for plants that absorb nutrients through their roots
- They contain all of the nutrients your plants need to thrive
- They’re safe for fish and invertebrates
- They contain relatively small doses of macronutrients
- They’re only suitable for plants that absorb nutrients from their root systems
2. API Root Tabs
These root tabs contain potassium, nitrogen, phosphorus, iron, and several other micronutrients that will leave your aquatic plants looking healthy and full. All nutrient levels are relatively low, so you may need to supplement these tabs with another fertilizer if you notice a deficiency of one of the nutrients.
These tabs dissolve very rapidly, so they can be a bit challenging to get into the substrate quickly enough. Once dissolved, they maintain a healthy level of nutrients, but they also make your tank water rather cloudy.
These are affordable, but your total may add up if you need additional nutrients.
- The formula helps limit overdosing of any single nutrient
- The tabs dissolve to fertilize your substrate quickly
- They contain at least trace amounts of all necessary nutrients
- They are very affordable
- The tabs dissolve too quickly sometimes to get them buried properly
- They make your water cloudy
- You will likely need to supplement with other fertilizers
Aquarium Plant Fertilizer FAQs
Is Aquarium Plant Fertilizer Safe For Fish?
Aquarium plant fertilizers are generally safe for fish, invertebrates, and the healthy bacteria residing in your filtration system. The nutrients can become a problem for your tank inhabitants if you over-dose. Overdosing is more often an issue for macronutrients than micronutrients, as larger quantities of nitrogen, potassium, and phosphate are needed for plant health.
If you follow the dosing directions carefully and have proper water testing kits for the nutrients you’ll be adding, you can ensure that your fish and other organisms remain safe while maximizing the benefits of fertilizing your aquatic plants.
When Should I Fertilize My Aquarium Plants?
We recommend adding fertilizer to your tank within the first few days of introducing your plants to the environment. Transplanting can be stressful for a plant, so providing them with the necessary nutrients right away will help them root and flourish, giving them a head start on growth.
The frequency with which you fertilize your tank will depend on several factors, including the volume of plants in your tank, the type of plants, and the kind of fertilizer you use.
The more plants you have in your tank, the more fertilizer you’ll need and the more often you should dose your water. Each plant you have will require the nutrients you’re adding, so you’ll want to test your water regularly to ensure you’re dosing the appropriate amount. Once a week may be adequate for one tank, while daily applications might be required for another.
The types of plants you have in your tank can help determine how frequently and how much you dose as well. More rapidly growing species will require a larger volume of nutrients. Plants like Hornwort and Waterweed may need more frequent fertilizing than Anubias and most mosses.
Lastly, the type of fertilizer will often determine dosing frequency. Liquid fertilizers may need to be added to your tank daily or every other day. Root tab fertilizers can often be effective with monthly dosing, while pre-packed substrates can often be useful for a year or more with proper care.
Can Liquid Fertilizer Kill Fish?
Liquid fertilizer contains high concentrations of nutrients that can be harmful and even fatal to fish if dosed inaccurately. Specifically, elevated levels of nitrogen and copper can kill fish and invertebrates and may interfere with healthy bacteria growth in your filtration system. You should always take great care to follow dosing recommendations and monitor your nutrient levels with regular water testing. You should also be careful whenever dosing a shrimp tank.
How Do You Fertilize a Planted Aquarium?
The process of fertilizing your planted aquarium will depend on the type of fertilizer you get.
If you’re using liquid fertilizer, you simply dose your tank according to the directions by measuring and adding fertilizer directly to the water.
If you’re using fertilizer root tabs, you’ll bury the recommended number of tabs in your substrate. The tabs will dissolve over time and fertilize the plants with roots in your substrate.
Finally, if you’re using a pre-packed substrate, you add the substrate to your tank just like you would any standard sand, gravel, or river rocks.
How Can I Make Aquarium Fertilizer at Home?
You can make a DIY aquarium fertilizer by mixing potassium sulfate (sulfate of potash), potassium nitrate (KNO3), and hydrated magnesium sulfate in a ratio of 2:1:5. Many of these ingredients are available online, and you can find some in major retailers.
Many aquarists add chelated metals in trace amounts to their homemade aquarium fertilizer, but you can supplement micronutrients with SeaChem Flourish Freshwater Plant Supplement for ease of use and ratios.
Does Miracle Grow Kill Fish?
Miracle Grow products may be useful for some aquatic plants, but they are toxic to fish and invertebrates. The chemicals can leach ammonia into your aquarium water, which can quickly pollute your tank. Additionally, the nutrient levels will likely be very high in a planted tank with these terrestrial fertilizers.
As such, you should avoid using Miracle Grow products in any tank that will house fish, snails, crabs, or other non-plant organisms.
Planted tanks can be very appealing, adding tons of natural beauty to any room. Maintaining healthy, vibrant aquatic plants can be very challenging, but aquarium plant fertilizers help add the necessary nutrients to help your plants thrive.
Our favorite planted tank fertilizer is the SeaChem Flourish Freshwater Plant Supplement. It provides all of the nutrients your aquarium plants need in small enough quantities to be completely safe for fish, invertebrates, and beneficial tank bacteria. Are you an aquarist who uses fertilizer in your fish tank? Did you see a major change before and after using fertilizers? We would love to hear about your experience.