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Can You Use Plant Fertilizer In Aquarium?

Aquariums with lots of real plants are becoming increasingly popular recently. They’re beautiful and create amazing ecosystems for the fish and plants alike. Keeping these plants healthy and happy is vital to the tank. Plant care begins in the soil, so you might be wanting to use your garden fertilizer just to give your aquarium an extra boost. But is it really a good idea?

You should not use regular plant fertilizer in your aquarium under any circumstances. Most plant fertilizers contain ammonia and can increase the amount of nitrates in your aquarium, both of which can be detrimental to the water quality. However, there are some aquarium-safe fertilizers on the market.

In this article, you’ll learn why you shouldn’t use regular plant fertilizer in your aquarium and what you can use instead. In addition, you’ll learn how to introduce a new fertilizer into your tank’s ecosystem to ensure that you don’t cause harm to anything in it.

Should I use Regular Fertilizer in my Aquarium?

can I use plant fertilizer in aquarium
Standard plant fertilizer can be purchased from almost anywhere, and it’s inexpensive. That’s why picking up a bag on your way home from work and sticking it in your aquarium can be so enticing.

You should not use just any old plant fertilizer in your aquarium because of the chemical compounds it may contain. Using it can be harmful to your fish and your plants.

What Could Go Wrong?

Several issues could arise if you use regular plant fertilizer in your aquarium. These can include:

  • Throwing off the balance. Balance is critical in an aquarium, as every little change could and will impact the water quality, whether it be in the pH, the alkalinity, ammonia, nitrates, or nitrites. Fish and aquarium plants are extremely sensitive to issues with water quality, and the smallest change could be fatal.
  •  Creating algal blooms. An increase in one chemical or another could lead to a bloom of algae. For example, excessive nitrates can trigger a brown algae bloom, but excessive phosphates can trigger a green one. These can become out of hand quickly and deprive fish and plants of essential nutrients, not to mention the impact it’ll have on your aquarium’s overall appearance.
  • Casualties. Fish and plants in aquariums can be very sensitive to change. Chemical imbalances can cause issues like burns and even ich to occur in your fish. However, the stress alone of the influx of chemicals can cause both fish and plants great amounts of stress, which is enough to kill them.

If you have to choose between using regular plant fertilizer in your aquarium and letting your plants essentially fend for themselves, choose the latter until you can find a better option.

Do Aquarium Plants Even Need Fertilizer?

can I use plant fertilizer in aquarium
Plants can get a lot of the nutrients they need from fish food and the waste that the fish produce. There are a few types of plants that can technically do without fertilizer, such as the java moss and java fern. However, for most types of aquarium plants, you do need some type of soil.

What Can I Use?

Part of the appeal of using regular old garden fertilizer is that it’s easy to find and inexpensive. You can get special aquarium soils from most pet stores. However, if you really need to, you can also use organic potting soil.

Organic Potting Soil

Organic potting soil is generally okay for use in an aquarium because it doesn’t contain as many harsh chemicals as a non-organic soil would. The thing to remember above all else with an aquarium is that your plants are going to get a lot of what they need from the fish they live with, whether from their food or their waste. You can usually find a decently sized bag of organic soil at your local garden center, hardware store, or even online.

However, organic soil can also get expensive, and depending on the size of your aquarium, you might buy too much. Soil in an aquarium, like gravel, doesn’t need to get changed very often (every 1-2 years), so you may find yourself with lots of leftover soil.


  • Easy to find
  • Not harmful to fish
  • Extra soil can be used elsewhere


  • Expensive
  • Can get messy
  • Usually only sold in large quantities

Aquarium Soil

Aquarium soil is the best option. It is specially made for aquariums, and therefore has everything a plant will need. If you’re looking to get serious about your planted tank, it’s certainly worth the investment. Usually, aquarium soil is clay-based, meaning it comes in little beads instead of loose particles, which can create less mess in the tank.

However, aquarium soil is harder to come by than organic potting soil. You can usually only get it in-store from pet stores, which might be a less convenient stop for you than your local grocery store. In addition, though, it can also get pricey. With this type of soil, you might not even need a fertilizer.


  • Less messy
  • Specially engineered for planted tanks
  • Won’t need a separate fertilizer


  • Hard to find
  • Expensive

Fertilizing Your Aquarium

If you find yourself making a choice that requires a separate fertilizer, there are plenty of options on the market. The most popular option is liquid fertilizers, which can be found in most mainstream fish care brands, like Seachem and API. These go directly in the tank and, since they’re not in the form of regular plant fertilizer, they create no mess.

Be careful not to overdo it with any kind of fertilizer. Even though they are meant for aquariums, they do still contain things like nitrates and nitrates, because plants need that to thrive. If you notice any kind of blooms of issues in testing, lay off of the fertilizer for a little bit until it subsides.

However, if you desire solid options, there are also pellets and tablets that you can buy. To use this kind of fertilizer, you can just place them in your soil and they’ll dissolve on their own. When adding any loose items, like pellets or new soil, always do so with a funnel rather than pouring it right in as that can both create a mess and clog your filter.

Final  Thoughts

You can and should use plant fertilizers in your aquarium, but you need to make sure they’re aquarium-specific and safe to use. If you opt for actual aquarium soil, you might not need a secondary fertilizer, but it’s good to get a bottle to have on hand anyway.

If you choose to use a different kind of soil, you definitely need a secondary fertilizer. Always make sure to keep up with the filter and do regular water quality checks. Otherwise, your plants won’t do well, fertilized or not. Happy planting!

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