Can You Use Aquarium Water for Perennial Garden & Outdoor Vegetables? Answered

Each individual can waste about 30 gallons of water every day without even realizing it. As an environmentally-conscious person, you’ve probably implemented measures to reduce water waste in your home. And reusing water might not be a new concept. If you run the tap to water your plants, you may have thoughts of occasionally replacing your tap water with fish tank water instead of discarding it. 

But is watering plants with aquarium water a good idea? In other words, is fish tank water good for perennial gardens and vegetables? The fishes may no longer appreciate the dirty aquarium water, but your perennial garden and outdoor vegetables will thank you. The fish tank water is rich in nutrients that plants need to flourish. However, there are a few exceptions to keep in mind. 

Stay with us to learn more about watering plants with aquarium water. 

Is Fish Tank Water Good for Perennial Garden and Vegetables? 

The microbes (good bacteria) in your aquarium break down the leftover foods, dying plant materials, and waste from the aquatic animals. The decomposition process gives rise to the level of nitrates and phosphates. 

The perennial plants and vegetables in your garden require nitrogen, phosphorus, and potassium in the highest quantity. And your fish tank water could be concentrated with these nutrients, typically depending on how often you change the water. 

A sufficient supply of nitrates could boost the amount of chlorophyll in your plants, increasing their photosynthetic efficiency. The plants will produce bolder foliage or healthy flowers and seeds. As for the phosphates, these compounds help with root growth, tillering, and plant maturity. 

When Not to Irrigate Your Garden Using Aquarium Water 

Even though watering plants with aquarium water offers beneficial nutrients, it may not be the healthiest choice, especially if it is the plants you plan on eating. 

If the aquatic animals are infected with zoonotic diseases and parasites, applying the water in your garden can put your family at risk. For example, salmonella can get into the soil and colonize the plants. However, the salmonella strains usually pose a non-negligible threat. 

On a positive note, it’s alright to use aquarium water in a garden with veggies and edible plants if you don’t add chemicals to the fish tank to regulate pH. And it’s not only about pH-regulating chemicals but also aquarium treatments for killing algae and preventing fish diseases. 

You’ll also want to avoid watering your perennial garden and outdoor vegetables with fish tank water in case you: 

  • Own a saltwater aquarium – You are irrigating your garden to hydrate the vegetable plants. Unfortunately, saltwater has the opposite effect. While plants also need salt to grow and produce, high concentrations will do more harm than good. Plants will show signs of wilting and reduced growth. 
  • Have neglected your aquarium in ages – If you haven’t changed filters or deep cleaned your aquarium as recommended, the water might contain high amounts of nitrogen, potassium, phosphorus, and ammonia. Unfortunately, too many of these nutrients can harm or even kill your plants. For instance, excessive nitrogen in the soil could lead to more leaves but less fruit.

Can You Replace Fertilizers With Aquarium Water or Use Both? 

Since fish tank water can supply the nutrients you see on plant fertilizers, replacing the store-bought fertilizers with aquarium water may seem a sensible thing to do. You will save money in the process. However, the answer depends on the tank size, contents, and cleaning pattern. 

If you change the aquarium water regularly, such as weekly, the plants may not get enough nutrients from that fish tank water alone. Therefore, you cannot do without artificial or organic fertilizers. 

If you have a lot of aquatic plants in the fish tank, they will reduce the nutrients in the water. As such, you can use both. 

In case the aquariums are large with a couple of plants and have messier fishes like goldfish, watering plants with aquarium water should suffice. 

If you have to dilute the fish tank water to have enough for your perennial garden and vegetables, there’s probably no harm in supplementing with fertilizer. 

It’s fair to say there’s no definite answer to this question. You may have to use the trial and error method to see what works best for your vegetable and perennial plants and flowers. 

How to Use Fish Tank Water in Your Garden

You don’t need special equipment to collect water directly from the tank for watering your plants. You can use a hose, siphon, or gravel vacuum to draw the aquarium water into a large bucket. 

The more the water looks dirty, the more nutrients it is likely to carry. If the fish tank water is not murky, you can take the bucket to the garden and start watering plants right away with a can, cup, or ladle. This is often the case if you do partial water changes. 

If you are changing all the water in the tank, it will be highly concentrated in nutrients. Such aquarium water will need to be diluted with fresh water before you can use it, especially on delicate vegetable plants or seedlings. 

Can You Use Aquarium Water for Perennial Garden & Outdoor Vegetables? The Takeaway 

Discarding fish tank water could be a waste of nutrients. Aquarium water packs a lot of essential plant nutrients. Besides nitrogen, phosphorus, potassium, and ammonia, fish tank water also accumulates beneficial micro-organisms that may help improve soil health and function. In some cases, you may not need store-bought fertilizers in your garden. On the flip side, delivering too much-concentrated aquarium water could lead to overfeeding your plants with nutrients. But you can always dilute the water before applying it to your vegetable or perennial plants.

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