What is The Best Water to Use in Your Fish Tank

By Eddie Waithaka @aquariawise

What is The Best Water to Use in Your Fish Tank

Aquatic pets are some of the most exciting animals you can ever keep in your home. The calming zen of watching them swim is on another level, plus you can interact with your fish while feeding them in case you need some lively-action.

The only downside is that they are fragile and need a very definite environment to survive and thrive, including the water you keep them in and the food you feed them.

For this reason, knowing what water to fill your aquarium with and the parameters to keep an eye on is a standard skill when starting the hobby.

Overall, tropical fishes will survive and thrive in tap water as long as it’s not filthy or filled with chemicals such as chlorine. If in doubt, you can have it tested just to be sure.

Adding a conditioner with every water change also goes a long way.

Take a close look at the water analysis from your local department. Though the results might vary from day to day, you’ll still be able to make informed decisions from the numbers you get from one review.

RO water is not a must when keeping tropical freshwater fish but might be necessary for saltwater tanks. In case you decide to use it in your freshwater aquarium, make sure you remineralize since it’s often too pristine for most fishes.

Tap water is also cheaper than RO water.

Below is all you’d need to know about aquarium water in better detail. Please read on.

Using Tap Water in Your Fish Tank

Ordinary tap water is the best and the most affordable to use in a fish tank, considering the whole hobby revolves around a safe and clean aquatic environment.

Even so, it is recommended that you let your water sit for several days before adding fish in all this while conditioning it to remove chlorine and other elements that may be harmful to your fish.

Please note that many governments allow treatment plants to use chloramine and chlorine to disinfect drinking water. But although the amounts used are safe for human consumption, they are often harmful to most ornamental fish kept in home aquariums.

It is also not uncommon to find minerals and heavy metals such as iron, copper, and calcium in tap water, hence the more reason to make your water safe for use in a fish tank.

That said, remineralizing your tap water before filling your aquarium is equally crucial since the natural process the water goes through not only adds trace elements, but also strips others, which are helpful to your fish survival.

How to Prepare Tap Water For Use in Your Fish Tank

Probably the first and most important step while preparing tap water before placing fish in is dechlorination. This is so because all the trace elements from disinfectants are the one chemical you will not miss.

Chlroine based disinfectants are harmful to fish, damaging their delicate gills and skin surfaces. Fish that are exposed to high levels of chlorine will show signs of irritation, such as swimming erratically or attempting to leave the water.Aquarium Wiki.

At lower levels, chlorine from disinfectants may not necessarily kill your fish but can still harm them.

Chlorine damage to the gills is especially severe breathing difficulties. Affected animals may exhibit fast gill beats and gasp on the surface in an attempt to get enough oxygen into their tissues.

The symptoms can easily be mistaken for oxygen deficiency, parasites, or some sort of disease; read more here.

How To Dechlorinate Water For Fish

The most artless and least expensive way of dechlorinating your tap water for use in a fish tank is by use of chemical dechlorinating products (simply referred to as conditioners), which you will readily get in your local fish store.

But please note that not all products are the same. Ideally, you want to get a brand like API stress coat water conditioner that will remove chlorine, chloramine, and ammonia in water, plus replace your fish’s protective coat all in one go.

The dosage of each product is also slightly different, so remember to refer to the label on your purchase.

That said, most conditioners will require you to use a drop of conditioner for between 0.5 to 2.5 gallons of water or 0.5 to 1 teaspoon for every 10 gallons of water. You’ll only need to add the amount to the water you intend to replace in your tank and not the whole volume.

Another solution that might work as well as conditioning is passing your tap water through an under sink RO filter, but make sure it is a quality model that is designed to remove chlorine, chloramine, and ammonia.

A simple faucet or under-the-counter drinking water carbon type filter will work as well if you make sure your water is allowed enough contact time with the filtration media.

Because chloramine exhaust carbon much faster than regular aquarium water, ensuring you purchase a tap-water unit that has an indicator that tells you when its time to change your cartridge is recommended.

One last hack that might help is aerating your fish tank water with an air pump before adding your fish to the tank. The circulated current will aerate your fish tank and help remove chlorine.

How to Remove Heavy Metal From Water For Aquarium Use

Tap water from local departments has trace minerals and heavy metals together with chlorine and chloramines. And albeit many of these elements not being harmful to fish per se, some like copper and iron are known to cause serious harm to fishes like koi and inverts such as shrimp and snails.

Miinerals like phosphates and silicate also encourage algae growth by providing them with nutrients to feed on. Calcium, on the other hand, forms a white residue on aquarium glass surfaces, which although not harmful to fish, can be quite unsightly and filthy.

For that reason, expelling these minerals and metals from tap water when in excess amounts is recommended.

Some water conditioners can detoxify heavy metals, allowing them to precipitate so they can be removed by your filtration. But you will need to have a chemical filter media for superior efficacy.

Use chemical sponges that will remove metals as water passes through them. Products like Poly filters or resin-based water purifiers work great at removing unwanted trace elements.

Poly filters are a specially formulated material bonded to a synthetic matrix that can absorb and adsorb contaminants and other toxic materials. They’ll remove heavy and normal organic loads, ammonia and nitrites, heavy metals (copper, iron and free copper iron, aluminum, lead), phosphates and tannins, and humic acid.

If filters do not work as you expected, use your under sink RO drinking water filter to rid the metals, then remineralize your water by adding items such as seachem replenish, and potassium bicarbonate, baking soda (sodium bicarbonate) or alkaline (acid buffers) to maintain the right ph.

Can You Use Purified (Bottled) Water For Your Fish Tank

Purified water is water that has been filtered or processed to remove impurities like chemicals and other contaminants, usually produced from ground or tap water.

Bottled or RO water is sometimes used interchangeably with purified water. But in some countries where public drinking water is filtered and processed, the term might also encompass unbottled or RO sources.

That said, purified water like any water will support aquatic life in aquariums, but in the case of reverse osmosis water, it lacks minerals essential to your fish’s development.

This means that if you decide to add water from a RO source in your fish tank, you will also need to remineralize it with products like replenish and ph buffers, and even conditioners to create an ideal environment for your fish.

Please note that keeping your fish in water that lacks these essential minerals and no buffering capacity will gradually kill your fish, even if the effects are usually not apparent in the beginning.

On the flip side, bottled water purified for human consumption will have some amounts of minerals, including iodine and chemicals such as chlorine, some of which are unsafe for fish, particularly in excess quantities.

The water is usually also devoid of oxygen, so it would also need to be oxygenated first.

In other words, bottled-mineral water does not guarantee the survival of your fish either.

So, I would suggest you use regular tap water and buy ideal anti-chlorine agents to make it safe for your fish. It is more accessible and will even cost you less in the long run.

See more below.

Using Distillled (RO) Water in Your Fish Tank

Overall, it’s unnecessary to use RO water for freshwater aquariums, though it’s strongly recommended if you don’t trust your tap-water source.

However, RO water is quite necessary for saltwater and reef tanks because they are notoriously difficult to maintain. It’s a great starting point for new marine aquarium owners and reefers seeking to create ideal water conditions for their fish and coral.

Reverse osmosis water is entirely free from chemicals toxic to fish like chlorine and chloramine, is neutral ph, and contains no water hardness, which allows you to control the parameters of your water chemistry, meaning you can support whatever aquatic life your desire.

The only con of using RO water is the water is usually too pure for fish to live in. Therefore, you will need to remineralize it to make it ideal for your tropical fish and corals.

Preparing RO Water for Freshwater Aquarium

Once you’ve obtained the contaminant and mineral-free water by reverse osmosis, you’ll now be able to regulate the water profile to best match your fish’s needs.

But you’ll need to adjust some parameters to ensure the water is well constituted for a fish’s survival.

The three benchmarks you need to check are the general hardness (GH), carbonate hardness (KH), and the ph balance of the water.

In general, most tropical fish will either want a softer, acidic environment or favor a harder-alkaline setting.

Raising The General Hardness (GH)of RO Water for Fish Tank

General hardness of your water is the measurements of calcium and magnesium content.

The more minerals present in the water, the harder it will be.

Therefore, to raise the GH (general hardness) of your RO water, add mineral-rich limestone or crushed coral, and aragonite can be mixed with your substrate. These are made of calcium carbonate and will increase the general hardness of your tank as they dissolve.

Even so, make sure you do not raise the levels too far unless your plan on keeping species like African cichlids that prefer thing on the harder-more alkaline side.

Raising The Carbonate Hardness (KH) of RO Water for Fish Tank

Carbonate hardness measures carbonate and bicarbonates present in water, which acts as buffers to your aquarium ph.

So, to increase your water KH, add sodium carbonate or bicarbonate (soda ash or baking soda) or add alkaline buffers (available in pet stores) in your water.

Natural media that raise your water GH, such as aragonite and crushed coral, can also be used to increase your aquarium KH, but they will impact the ph as well.

How to Buffer The Ph of RO Water for Fish Tank

Buffering your RO water ph for use in your fish tank is not too technical, more so because most remedies that increase the GH and KH of your water will impact ph.

Crushed coral and aragonite will slightly boost your water ph. Limestone can also be added to elevate both the ph and general hardness.

Small amounts of baking soda will work to increase the KH and water ph. But the best way to target the ph independently is to add a store-bought buffer such as seachem alkaline buffer.

That said, please exercise extreme caution when buffering your water ph or down because significant swings will very likely kill your fish.

Learn much more about using RO water in your fish tank: general hardness, carbonate hardness, and ph in this full article on Freshwater systems website.

If you are located in the USA (more so Florida) and are looking to buy tropical (freshwater ) mentioned in this or any other post (and more), check out Consolidated Fish Farms Inc.

Also Consider usingAquariawise Coupon Code for a 10 percent discount on eligible purchase. They are a great source for healthy aquarium fish, plus we get a small commission with no extra cost to you.

Happy Fish Keeping🐡🐟🐠.

← All articles

The Aquarium Club ↓

Join the 37k+ strong aquarium community

The AquariaWise Newsletter is known for cutting through the noisy world of pet fish keeping showcasing stunningly breathtaking aquarium fish and superbly insightful aquarium plants to help you bring out the peace and serenity you seek with your aquariums. And it doesn't stop there... think aquarium fish care, plant care, building fish tanks, everything aquariums... you'll be right at home.