Can You Use Well Water In A Fish Tank? (Hint: It Depends)

🀝 Our content is written by humans, not AI robots. Learn More

If you get your water from a private well, you might wonder about its suitability in a fish tank or home aquarium.

This guide answers the question: “Can you use well water in a fish tank?”

πŸ“Œ Key Takeaways:

  • You might be able to use untreated well water in your fish tank, depending on the impurities your well contains.
  • If your well water contains heavy metals, salt, or minerals, you may need to filter the water before using it in your fish tank.
  • Alternatively, use distilled water, reverse osmosis water, or filtered bottled water in your aquarium.

πŸ€” Can You Use Well Water For Fish Tank?

You can use well water in a fish tank. However, well water may contain contaminants that are harmful to aquatic life, such as heavy metals, nitrates, and hydrogen sulfide. We recommend testing your water before using it in a freshwater or saltwater fish tank.

If harmful contaminants are discovered, consider buying a water filtration or purification system or using distilled water as your tank water instead.

Using well water for fish tank

πŸ”Ž How To Know If Well Water Is Safe For Fish Tanks

Conducting a water test is the best way to know whether or not it’s safe to use well water for your aquarium.

Choose a certified testing laboratory for the most accurate results. You can either test for specific contaminants that are known to be harmful to fish (see the list below) or buy a well water testing package that detects a range of the most common impurities in groundwater supplies.

Even as little as 0.5 PPM (parts per million) of a contaminant in your well water might be enough to harm your fish species. So, if any potentially dangerous contaminants are detected, even in small amounts, it’s likely unsafe to use well water for your fish tank.

Water testing with tap score

🧫 Potential Harmful Contaminants In Well Water

Wondering which potential well water contaminants may be harmful to your fish? Below, we’ve shared the top impurities to be aware of.

  • Nitrates and nitrites – Natural compounds of nitrogen and oxygen which cause stress, and disease, and inhibit a fish’s ability to reproduce.
  • Hydrogen sulfide – A colorless gas, known for its rotten egg odor, which interferes with the respiration process and potentially causes stress, reduced appetite, sideways swimming, and death in fish.
  • Heavy metals – Including cadmium, copper, and zinc. Lead may also leach into your water if you have lead pipes. In high amounts, heavy metals are dangerous to aquatic life.
  • Hardness minerals – Certain fish species can’t survive in hard water (tap water that contains a lot of calcium and magnesium minerals). Fish may experience stunted growth or organ damage as a result of high mineral exposure.
Well being replenished by rain water

πŸ†š Well Water Vs City Water For Fish Tanks

You’ve probably read warnings about adding normal tap water to a home aquarium. These warnings assume that your water comes from a municipal supplier.

Municipal water, or city water, contains chlorine and other harmful chemicals that are used to disinfect the water supply. Chlorine is one of municipal water’s most dangerous chemical components and will kill fish if the water isn’t left to sit for 24-48 hours, allowing the chlorine to evaporate, before use in an aquarium.

Thankfully, well water is usually chlorine-free. The only exception is if you’ve recently shock-chlorinated your well, and may have traces of chlorine leftover.

However, well water often contains higher levels of other contaminants that might harm your fish tank’s inhabitants, including nitrates, heavy metals, and hydrogen sulfide, compared to your city’s local water supply.

So, well water may also be damaging or even fatal to fish – it just depends on what exactly your well water contains.

πŸ†š Well Water In Freshwater Tank Vs Saltwater Tank

Generally, freshwater fish aren’t quite as sensitive to contaminants as saltwater fish. So, untreated well water may be dangerous to use in saltwater and freshwater tanks – but especially so in saltwater tanks.

Freshwater and saltwater fish have different preferences and requirements for water parameters and pH.

πŸ“Œ Most saltwater fish need a pH range of between 8.0 and 8.4, while most freshwater fish need a pH of 6.8 to 7.8. The normal pH range in wells supplied by groundwater is 6.0 to 8.5, while shallow or surface water wells have a pH range of 6.5 to 8.5.

There are commercial products and DIY remedies (like baking soda) that can be used to adjust your water’s pH level in a fish tank if necessary.

πŸ“– How To Make Well Water Safe For Fish Tanks

There are two ways to guarantee safe well water for fish tanks: water filtration and conditioning.

Filter Your Water

Unlike municipal water, well water isn’t filtered before it reaches your home. It’s your job to treat it, if necessary, to make it safe to drink.

Well water has the advantage of being naturally filtered by layers of rock as it seeps into the aquifer – but that doesn’t guarantee that it’s free from nitrates, heavy metals, and other contaminants that could harm fish.

Good filters to use for well water are:

  • Air injeciton/oxidation systems – Remove iron, hydrogen sulfide, and manganese
  • Reverse osmosis filters – Remove virtually all impurities from well water
  • Water distillers – Purify water in small batches
  • Whole home heavy metals filtration systems – Target lead, cadmium, copper, zinc, and more

You’ll also need to soften your water if you have a hard well water supply. Many types of fish are affected by exposure to hardness minerals. But many fish don’t do well with the high sodium content of salt-softened water, either, so you might need to further treat your soft water to make it safe for a home aquarium.

Water softener and whole house filter

Condition Your Water

Water conditioning is the second stage of water treatment that we strongly recommend. You should condition your water whether it’s normal tap water or well water.

Water conditioners:

  • Neutralize chlorine and unwanted metals
  • Convert nitrates into nitrogen gas, which can dissipate from water
  • Adjust water’s pH (to some extent)

By conditioning your water, you’ll make 100% sure that it’s safe and ready for use in your fish tank.

πŸ“‘ Alternatives To Well Water For A Fish Tank

If your well water isn’t suitable for use in your home aquarium, there are a few alternative water sources to consider:

Distilled Water

Distilled water is water that has been boiled and separated from is impurities through evaporation and condensation. Distilled water is almost entirely pure, which makes it safe to use in a fish tank.

You can buy bottles of distilled water online or make your own distilled water with an at-home countertop water distiller.

Filling the imber isla water distiller

Reverse Osmosis Water

Reverse osmosis water is very similar to distilled water in that it’s almost 100% pure. The only difference is the water treatment process.

RO water is sent through a semi-permeable membrane, which separates the majority of total dissolved solids, including minerals, salts, chemicals, metals, and microorganisms.

You can buy reverse osmosis filters to treat your tap water at home or buy bottled RO water from most grocery stores and online.

Filtered Bottled Water

Finally, you can use filtered bottled water in your fish tank – just check that the filtration process has removed the contaminants that are dangerous to fish, since not all filtration processes remove the same contaminants.

Check on bottled water labels

πŸ“ Final Word

It might be fine to use well water for your fish tank. But keep in mind that even trace levels of nitrates, certain heavy metals, and hydrogen sulfide can also cause stress in both freshwater and saltwater fish, and toxicity occurs easily.

If you’re uncertain about the safety of your well water for a fish tank, get your water tested. You’ll either be reassured by the results or you’ll be able to install a water filtration solution that targets the contaminants highlighted by the test.

Water testing with tap score

❔ Can You Use Well Water In A Fish Tank? FAQ

How do I make my well water safe for my fish tank?

You can make your well water safe for a fish tank by filtering the water to remove potentially harmful levels of nitrates, heavy metals, hydrogen sulfide, and other contaminants affecting your water quality. If you want to be really safe, you could use distilled water in your tank to ensure no contaminants whatsoever are present.

Do you need to condition well water for fish tank?

No, you don’t need to condition well water for a fish tank – but we would strongly recommend it. The main role of a water conditioner is to remove chlorine and chloramine, which are only usually found in city water. However, water conditioners also correct water’s pH level, and some conditioners convert nitrate to nitrogen gas, allowing it to dissipate out of the surface of the water. This is useful for both city and well water supplies.

Is well water with a water softener safe for fish?

No, well water that has been softened by a salt-based softener isn’t safe for fish. Many saltwater and freshwater fish species, especially tropical and ornamental fish, are affected by the minerals in salt-softened water. It’s better to use distilled bottled water, which is 100% safe for fish, in your fish tank.

Is filtered well water safe for fish?

Yes, filtered well water should be safe for fish – as long as the water filter removes the impurities that are known to be dangerous to fish, like heavy metals and nitrates. Test your water after filtering it to check that it now contains no harmful contaminants.

  • Laura Shallcross
    Senior Editor

    Laura is a passionate residential water treatment journalist who holds an undergraduate degree in Print Journalism and a master’s degree in Creative Writing. Over a span of 5 years she's written on a range of topics including water softening, well water treatment, and purification processes.

Scroll to Top