Is Fish Tank Water Good For Orchids? (Let’s find out!)

Keeping the aquarium water fresh offers your lovely fish and floating plants a healthy environment. However, one should not change all the aquarium water with fresh one as it may be risky for the fish. People wonder if fish tank water is good for orchids.

Fish tank water can prove effective for the growth of your orchids. The water that may prove risky and unhealthy for fish is quite healthy for the growth of plants. Different nutrients make this kind of water a great fertilizer for plants

If you have aquariums and orchids, you can recycle fish tank water by feeding your orchids with it, as it may help in the faster growth of the orchid plants.

Read on to find out everything you need to know for successfully growing and caring for orchids in fish tank water. You might also enjoy reading: What Are The Differences Between Tulip And Rose?

Is Fish Tank Water Good For Orchids?
Is Fish Tank Water Good For Orchids? (Let’s find out!) –

Orchids Characteristics

Most orchids are known to be Epiphytes, which means they grow on other objects and stick to rough bark or even stone. The more popular orchids are phalaenopsis hybrids (AKA moth orchids) and dendrobium hybrids.

To successfully grow an orchid, it is essential to understand its needs and requirements. The rule of thumb for successfully growing orchids is to duplicate their natural conditions as closely as possible.

Below is a table containing orchid plants’ characteristics.

Genus nameOrchidaceae (1)
Common NameOrchid
Orchid plants number of genera600
Plant typePerennial flower
Light requirements– Bright
– Indirect light
Soil TypeWell-draining orchid soil mix and aerated
pH requirements5.5 to 6.5
Watering requirementsWater your orchid once a week and allow the soil to dry out between waterings partially.
Orchids require high humidity and airflow around the roots, with regular drying periods alternated with heavy watering.
– To determine your orchid’s water needs, frequently check the soil until you.
Orchids temperature requirements50 to 85 F (10 to 29.45 C)
Fertilizer requirements – During the growing season, feed your orchids weekly with a weak powder or liquid fertilizer solution.
– In winter, don’t fertilize your orchids; keep it warm, and cut the water back to once a month. Ensure it stays hydrated by misting it frequently.
Orchids container requirements – The most appropriate size container to grow orchid is between 4 to 6 inches (10.16 to 15.24 cm) in diameter.
– It is best to use shallow pots because orchids spread their roots to the sides and not down.
– In a greenhouse-type environment, orchids thrive hanging baskets or mounted on slabs.
Orchids Plants Characteristics –

Is Fish Tank Water Healthy For Orchids? 

It is safe to use fish tank water for orchids because fish tank water contains beneficial bacteria, potassium, phosphorus, nitrogen, and trace nutrients to promote healthy plant growth.

But, avoid using the tank water of orchids or any other houseplants if you treat the fish for diseases. It is also a good idea to alternate with some pure water once in a while.

For best results:

  • Ensure you know your fish tank water parameters, including total dissolved solids (TDS), pH, nitrates, and hardiness.
  • Also, remember that aquarium water is generally pretty “dirty” compared to the water quality your orchids would receive in nature, so you might consider mixing the tank water with RO water
  • You could also mix tap with reverse osmosis; ensure you let the tap water sit out for a day before eliminating the chlorine. You just need to put the water in an open container and let it sit for one or two days, and the chlorine will evaporate. Mixing rain or RO water with a small amount of tap water might make the aquarium pH more stable. Even though the nitrogen measurements are reasonable, it might become more acidic with only rain or RO.
  • Do not water your house plants, including orchids, with fish water if you have added any of the following to the tank: aquarium salt, any fish medication, and chemical, including pH adjusters or algae killers. Adding algae ridding chemicals (pesticides) is generally more harmful than good for both your orchids and fish.
  • Also, ensure you properly maintain your fish tank, it will not stink.
  • Old aquarium water is excellent for orchids, particularly if you have fish that create a lot of waste, such as goldfish.
  • If you provide your orchids with the right amounts of water, light, food, and warmth., they will not develop any issues.  
  • Different useful constituents of the fish tank water make it fertilizer for the plants. Here are some nutrients available within the fish tank water.
    • A good amount of potassium
    • Adequate phosphorus
    • Beneficial bacteria
    • A healthy quantity of nitrogen
    • Some useful trace nutrients 

See also: How Long Do Flowers Actually Last Without Water (And how can you make them last longer?)

What Are The Benefits of Fish Tank Water for Plants? 

The main reasons people use fish tank water are 

  • Nitrogen
  • The bacteria in the fish tank water helps break down the nutrients for better absorption by the plants. 

Here are some advantages of using fish tank water for irrigation of orchids. 

  • It is a rich source of nutrients like nitrogen, phosphorus, potassium, etc. 
  • This water contains useful bacteria. 
  • Aquarium water is useful for killing harmful algae. 
  • It helps to adjust the pH level in plants. 

When Aquarium Water Proves Harmful for Plants? 

Normally, aquarium water proves very beneficial for plants. However, if it is diluted or has too much salt in it, don’t use it for your plants. Having too much salt may affect the growth of your orchids. 

The dirtier the Aquarium water, the more Ammonia and Nitrate amounts will be in your water. Don’t store it for more than a few days in a cool place because besides stinking bad, there are also chemical reactions (algae growth and other harmful bacteria) in stored aquarium water that might not be beneficial to your plants.

What Kind of Water Should I Use To Water Orchids?

Orchids are not similar to the normal plants planted in the soil. The plants in your orchids are usually planted in moss, bark, or any other component that has essential nutrients for the healthy growth of plants.

As these are planted off to the soil, they are relatively sensitive. Any negligence to them may result in their improper growth or even death. 

Being very sensitive but lovely plants, the growth of orchid plants is affected by improper irrigation for other reasons. Watering improperly is the major reason for the orchid plant’s death.

So, make sure that you use an effective kind of water for them and water them properly. In the later section, we’ll break down some effective kinds of water that will help in the healthy growth of your orchids. 

Generally, watering your orchid early in the morning is better, ensuring complete water evaporation on the foliage and the crown by nightfall. And the kitchen sink is the best place to water your orchid plant. You can use lukewarm water and avoid using softened salt.

You will need to regularly water your orchid plants if your house is hot or has low humidity. Water your orchid plant for about 15 seconds, and make sure you wet the media thoroughly.

See also: Here Are The Reasons Garden Furniture Is So Expensive?

Is Fish Tank Water Good For Orchids? (Let’s find out!) –

What Kind Of Water is Effective for Orchids?

Here are different kinds of water that may prove effective for your orchids. 

1- Rain-Water

Rainwater is a good choice for orchid plants as it has many essential nutrients such as healthy salts, pollen, dust, and lots of organic matter. But make sure that you use fresh rainwater.

If you store it for your orchids, make sure that you have made proper arrangements to store it. Prevent it from being overheated or being too cold. Also, cover it to avoid its exposure to dangerous chemicals. 

2- Tap-Water

If you manage to maintain the amount of chlorine that tap water contains, it could be the perfect option. It’s easily accessible and is also rich in different nutrients like hormones, bacteria, salts, chlorine, magnesium, and so on.

However, make sure that it has a normal quantity of all these nutrients. Such water varies from place to place. Hence, make sure that it is effective for plants.

3- Distilled Water 

Whether you use it for yourself or your plants, distilled water is a great idea. However, using it for big orchids may be expensive. So, make sure that it doesn’t cost you too much.

If you can manage it at a reasonable price or have a small orchid, it can be useful for your orchids.  

4- Well Water 

Well water, also called spring water, has many heavy minerals and excessive amounts of other nutrients. So, before using it, make sure that it is normalized to a normal nutrient level. 

See also: 3 Top Gardening Gloves For Thorns.

Is Fish Tank Water Safe For Plants?

Fish tank water is safe and effective for your plants only when it contains a normal amount of salt. The rest of the nutrients contained in this kind of water will help in the effective growth of the plant. 

Generally, the water that you think is dirty and inappropriate for your fish will prove very effective for your orchids. So, never make the mistake of throwing this water off without any useful use.

The feed of fish has many useful nutrients that keep on adding nutrition to the water. However, at a certain point, the water of the aquarium becomes unhealthy for the fish, but it is not useless at all. 

However, using salted water can do severe damage to your plant, particularly potter indoor plants.

Is Fish Tank Water Good For Potted Plants?

If you have plants potted in soil, fish tank water is good to use for them. However, if you have orchids, make sure that the aquarium water you’re using for them is not too alkaline. 

How Often Should Water Orchids?

Generally, it is recommended to water orchids once a week during the winter and twice a week when the weather conditions become warm and dry. In addition, the size of your orchid container influence how often you need to water your orchid plants, regardless of climate conditions:

  • A 6-inch container needs water every 7 days.
  • And a 4-inch container needs water every 5 to 6 days.

Tips For Caring and Growing Orchids With Fish Tank Water

  • Remember that orchids are epiphytes and would die if you leave them in water for any period. They are typically used to hanging out on the trees’ branches.
  • The most common orchid sold to the general public is the phalaenopsis orchid, which is relatively easy to grow.
  • Ensure you check the pH (ideal pH is 5.5 to 6.5) to ensure it is in the proper range for orchid growing
  • And if you are new, you can start with a few plants to see how the fish tank water affects them before committing completely. 
  • Avoid using fish tank water if you add any salt to your aquarium water for the fish.
  • Add orchid fertilizer every couple of weeks

See also: Are All Hydrangeas Actually Perennials?

Wrapping Up

If you’ve wasted your aquarium water by dumping it in the toilet or outdoors, stop making this mistake, as this water can help in the healthy growth of your plants.

However, make sure that this water is not too alkaline, as overuse of salt may harm the orchids. If you’re changing your fish tank water regularly, use it for irrigating your orchids, as it’s very beneficial for them. 


Hello friends, I am Altiné. I am SO excited you are here! I am the guy behind Plants Heaven is a blog that shares information about preparing, creating, and maintaining gardens in and out of your home, regardless of where you live. My goal is to help you learn to love gardening and reap the benefits that come with it. I am still learning; therefore, the information I share on this site may not always be “expert” advice or information. But, I do my VERY best to make sure the information shared on this blog is both accurate and helpful.

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