How To Treat Tap Water For Goldfish – Tips For A Healthy Tank

It’s a common myth that goldfish are an easier start to fishkeeping than tropical fish and that they don’t need as much care to keep healthy. Although you don’t need to keep their tank heated, you still need to maintain their water quality, and you need to know how to treat tap water for goldfish.

If you use tap water for your goldfish tank or bowl, you must first treat the water to remove chemicals like chlorine and chloramine. If these are not removed, they will damage your fish’s gills and organs. Read on for how best to treat tap water and keep your goldfish environment healthy.

Does Goldfish Water Need To Be Treated?

When you perform your weekly water changes for your goldfish tank or bowl, you’ll need to replace about 35% of your tank water with fresh, clean water. This helps to maintain healthy levels of nitrates and ammonia in the water, which keeps your goldfish healthy.

The other reason you need to perform these water changes is that goldfish are messy fish – they tend to make a lot of waste, and by leaving the water, this will accumulate, and your goldfish is likely to get sick and die as their water gets dirtier.

Most of us change the water with fresh tap water. However, this water must be treated to remove harsh chemicals like chlorine.

Your tap water will have chlorine in it to make it healthier for humans to drink. Chlorine is one chemical added to our water to kill bacteria and other pathogens, but you can treat your water to remove it. While the amount of chlorine in our tap water won’t bother us, it can be detrimental to your goldfish.

The biggest issues for goldfish in untreated tap water are chlorine and chloramine, which adds extra ammonia to their water. Not only are chlorine and ammonia bad for your goldfish, but they destroy the healthy bacteria that keep your biological filtration system functioning.

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Now that we understand why tap water needs to be treated for your goldfish, let’s look at the how.

How To Treat Tap Water For Goldfish

Several methods are available to treat water for your goldfish; some require leaving the water to sit, or you could use special aquarium water conditioners.

You should test the parameters of your water to see how hard or soft it is and what the ammonia levels are, for example. Keep your goldfish happy and healthy by taking the time to do these tests – it will make a great deal of difference and help you know what is causing issues in your tank.

Test Strips:

Soften Tap Water For Goldfish

First, goldfish prefer to live in soft water. Hard water has excess calcium and magnesium, which are not great for your goldfish. You might consider treating your water to soften it if you live in a hard water area, as the high mineral levels in hard water will affect the goldfish’s organs.

As easily 85% of the USA has hard water, you will need to tackle this issue somehow. The easiest way to soften hard water is to boil it. If you know you’ll be doing a water change, boil up the required tap water in advance and leave it to cool down to tap temperature.

Boiling the water causes the calcium and magnesium in the water to form a precipitate. When you pour off the water, be careful to leave the sediment on the bottom of the container behind.

However, boiling is not the most effective way to soften your aquarium water. One of the suggestions for softening your tank water is to add a water-softening pillow. The pillows are not left in the filter long term, just until the required softness is reached.

Condition Tap Water For Goldfish

How to treat tap water for goldfish also involves conditioning it before adding it to the tank so that you’re not adding unwanted chemicals and heavy metals into your goldfish’s environment.

Non-Chemical Methods To Dechlorinate Tap Water

You can leave regular tap water to stand for twenty-four hours, allowing the chlorine and chloramine to dissipate. You’ll need to leave it standing in an open vessel to allow the chemicals to evaporate. I used to use a large bucket and prepare the water the day before my weekly water change.

If you decide you don’t want to wait that long but don’t want to add conditioners to your water, you can use a UV light to speed up the dichlorination process. The UV light can be used to sterilize your water and kill algae effectively. You should avoid using this over your tank, directly on your fish.

Fishkeepers with large tanks requiring a lot of water to be conditioned often opt for Reverse Osmosis filters to remove chemicals from tap water. Still, these are not usually necessary in a smaller system like a small tank or fishbowl and are aimed at tanks of 100+ gallons.

Another option that some fishkeepers use is to collect natural rainwater for tank water changes.

Chemical Methods To Dechlorinate Tap Water

A relatively quick and easy way to dechlorinate and treat tap water is to buy water conditioning drops. This is probably the easiest method for treating water in a small tank.

However, if you have many or very large tanks, this can quickly become a pricy option, and you may prefer to invest in reverse osmosis filters instead.

Several brands of tap water conditioners are on the market, but all perform more or less the same job. They detoxify heavy metals in your tap water and remove chlorines and chloramines.

The conditioning drops are usually good value for money and will help protect your goldfish from irritated tissues, gills, and organs. Use these drops in your tap water at the recommended amount – 3ml per ten gallons of water.

How To Treat Tap Water For Goldfish

Other Treatments For Tap Water

Other times may arise when you need to treat the tap water you use for your goldfish. You can use Stress Coat to treat tap water for your tank before adding it. You can use this for weekly water changes or as an additional treatment when changes have stressed fish, such as adding new fish to the tank.

Suppose you accidentally added chlorinated water to your tank, which has upset the fish and destroyed the balance of bacteria in your biological filters. In that case, you can boost your tank by adding API Quick Start.

By using Quick Start, you add freshwater bacteria, which will help with the tank cycling process. You can also use this routinely in your tank when adding new fish.

Can You Use Bottled Water For Goldfish?

If you’re concerned about using tap water for your goldfish, you might be wondering if it’s possible to use bottled water instead. If you choose to top up your tank with bottled water, you must ensure that the water you buy is drinking quality.

It should NOT be:

  • Ionized
  • Flavored
  • Distilled
  • Demineralized

If you’re going to buy bottled water to use for your water changes, you should look to buy in bulk to keep the costs down. You will still need to condition the water to remove any chlorine or chloramine.

How To Change Water For Goldfish

Water changes are a weekly part of goldfish tank maintenance. The general rule is to remove and replace about 25% of the tank water every week with new, fresh water.

By performing regular water changes, you will keep ammonia levels down and remove dirt and waste that could decay and dirty your water. If your tank or bowl has gravel, you can use a gravel hoover to siphon the dirty water from the bottom of the goldfish tank and keep the substrate clean.

When you replace the dirty water with fresh tap water, always be sure to let it stand for 24 hours first or treat it with a suitable aquarium water conditioner.

Ensure that the new water matches the temperature of the water in the tank, as sudden temperature changes could shock and kill your goldfish.


As you can see, there are both natural and chemical options for how to treat tap water for goldfish. An aquarium water conditioner is hands down the quickest, easiest way to treat tap water and keep your goldfish thriving in their aquarium.

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