Can You Use Aquarium Water For Plants?

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Your aquarium may be home to plenty of beautiful fish and even aquatic plant life. But if you also keep a garden, it is totally natural to wonder can you use aquarium water for plants?

It is not only possible, but beneficial for most species of plants to be watered using average water from an aquarium. Because plant life requires nutrients to survive, and aquarium water is a natural source of some of the same nutrients, plants can thrive on aquarium water. However, this is only the case with freshwater from aquariums.

Although it seems pretty straightforward, there is a lot to unpack about the benefits and the disadvantages to watering your plants with aquarium water.

In this article we’ll go over what kind of aquarium water is acceptable to use on your plants, as well as the pros and cons of doing so. We’ll even answer some frequently asked questions! So let’s get started. 

Can You Use Aquarium Water For Plants?


The general answer to the question is yes, in most cases. This is because most aquariums which house fish naturally get pretty dirty with the detritus and debris that comes with the habitat of any living creature. 

While your fish may need you to swap this water out pretty regularly and return to a cleaner base of water to swim in, your plants actually can benefit from all of that dirt and algae.

What fertilizer does for your house plants by way of giving them potassium, nitrogen, or other helpful compounds, aquarium water can also do.

With that being said, there is a right way and a wrong way to use aquarium water on your plants, and disadvantages as well as benefits. Let’s go over them below:

Pros to Using Aquarium Water On Plants

  • Aquarium Water Has Nutrients – This is the main factor that should put you in favor of using aquarium water on your plants. Plants need nitrogen and other nutrients to survive. Usually, the best way to get them this is through manure, or fertilizer specifically made with this ingredient. However, aquarium water can provide these!
  • Aquarium Water is Cheaper Than Fertilizer – Because your fish will double as the producers of the nutrients that make aquarium water so rich in benefits, you may not even need to buy as much fertilizer. Aquarium water can fill that need for you!

Cons to Using Aquarium Water on Plants

As great as these benefits may seem, there are still some downsides. Let’s take a look at these risks below:

  • Aquarium Water May Not Be Rich Enough – Although really filthy aquarium water that is being switched out for the health of your fish can replace fertilizer, there is a chance that it simply won’t do the trick for some plant species. This is more likely if you switch your water out more than twice a month.

How to Use Aquarium Water on Plants?

Now that we’ve covered the pros and cons that mainly come into play when deciding to use aquarium water on your plants, let’s go over the best way to put that aquarium water to use! Check out the step-by-step guide we’ve prepared below:

  1. Check the Size of Your Tank – You will want to make sure your plants get the most out of each dose of aquarium water: however, if you have a small or even medium sized fish tank and numerous, thirsty plants, you won’t be able to replace all your watering routine with aquarium water. Keep this in mind so your plants are properly hydrated!
  2. Set Aside Old Tank Water During Water Change – You never want to simply scoop aquarium water out of your tank to give your plants a drink randomly. Instead, wait for your regular water change, and only set aside the old water for your plants. Fresh aquarium water likely won’t do your plants as much good, without as many nutrients.
  3. Check For Dilution Needs – The water that you use on your plants should be cloudy, as most exchanged aquarium water is after being filled with fish waste. However, if it is so murky that you can’t see through it, dilute it with clean water before giving it to plants. This will allow your plants to have plenty of nutrients without overfeeding them.

What to Avoid When Using Aquarium Water on Plants:

In addition to the cons that can be part of using aquarium water on your plants, there are actually some big factors to completely avoid when adding fishy water to the environment and care of your plants. These rules are listed below:

  • Never Use Saltwater – If you have an aquarium for saltwater fish and therefore use salt water, you absolutely cannot use this water on your plants and expect a healthy result. Only attempt to use aquarium water on plants if you own freshwater fish!
  • Do Not Forget Fertilizer – You need to have aquarium water that is both rich in nutrients, meaning it is rarely changed out, and plentiful enough to keep your plants hydrated and nourished. Otherwise, combine aquarium water with fertilizer.
  • Do Not Overfeed Your Plants – The potassium and other nutrients in aquarium water is great for plants, but not if it comes in too much abundance! Especially if you plan on combining fertilizer with aquarium water, make sure to dilute the foggiest waters for the greatest results.

Related Read: Can You Use Bottled Water In A Fish Tank?


Is aquarium water good for watering plants?

Yes, aquarium water is great for watering most species of houseplants and even some decorative plants outdoors. Plants need nutrients like nitrogen, potassium, phosphorus, and many more to survive. Usually, they get these from fertilizer. 

However, fish naturally produce these minerals in dirty water, so it is great to take that cloudy water during a tank water change and use it to water your plants.

Is aquarium water good for succulents?

Many people love succulents for their variety in size and color, as well as their hardy nature. Usually, these desert-dwelling plants do not require too much watering or care compared to other species of flora. 

However, aquarium water is usually not good for succulents. This is because a cactus, like a succulent plant, thrives best when it is able to grow gradually over a long period of time. Too much of a good thing, like the nutrients found in aquarium water, can cause your succulents to burst out in new growth. 

What this results in is usually a split succulent. It can even cause root rot, since your cacti may not be able to process the nutrient-rich water fast enough and is used to infrequent moisture. 

Related Read: How Long Do Aquarium Plants Take to Root?

Wrapping Up

To sum it all up, you can use aquarium water for houseplants, to the benefit of your plants’ health! For most plants, the very compounds that a fish’s waste produces turn out to be a superfood!

The exceptions to this are if your water is too cloudy with nutrients, meaning you could risk overfeeding your plants, or if you have saltwater, which should never be used on plants. Succulents and cacti should also not be watered using aquarium water.

In spite of these exceptions, it is still generally true that watering your houseplants with aquarium water is a great idea!

Recommended Read: Can You Add Gravel After Water In A Fish Tank?