You can’t see it…
You can’t smell it…
Often you can’t even taste it…
But this invisible assassin is an expert at killing your fish.
I am talking about disinfectants like chlorine and chloramine, found in your tap water.
To you and me, these disinfectants are considered harmless.
But to your fish, they are deadly.
Want to use tap water in your aquarium?
If you don’t remove these disinfectants, your fish will die.
Fortunately, water conditioner is what you need to do exactly that!
Today I am going to teach you everything you need to know about water conditioner
- What is water conditioner and what does it do?
- A quick history of aquarium water conditioner
- Do you need to use water conditioner?
- How often should you use water conditioner?
- What are the different types of water conditioners?
- Why you shouldn’t use water conditioner with a salt water tank
- Using water conditioner with a small tank
- The best water conditioner
What is water conditioner and what does it do?
When most people mention water conditioner, they are talking about a solution that you add to tap water to make it safe for your fish – it changes the condition of the water.
You see, the reason tap water is considered safe to drink is because it has chemicals added to it to kill bacteria and viruses.
The problem is, these chemicals not only kill your fish fish, but also the good bacteria inside your aquarium – the ones providing biological filtration to your tank.
By adding a water conditioner to your tap water, you can neutralize these chemicals, keeping your fish happy and healthy.
A quick history of aquarium water conditioner
At first, the only disinfectant in tap water that aquarists needed to be worried about was chlorine.
Chlorine was simple enough to get rid of – you could remove it by leaving the water to sit for an extended period of time or by boiling the water over night.
Then along came a game changer: Sodium thiosulfate.
When added to tap water, this compound instantly removed chlorine. Best of all, it was harmless to fish.
This could be considered the first water conditioner.
Then the game changed again.
Water supplies began to add both chlorine and ammonia to the water. These two chemicals combine to form chloramine.
If you were to just remove the chlorine, you would leave behind the ammonia, which is also dangerous to your fish.
And so a new water conditioner was introduced, one that not only removes the chlorine but also neutralizes the ammonia.
Nowadays water conditioners do so much more than just neutralize chlorine and chloramine…
They also remove metals like lead and copper, help get nitrates under control, and even contain additives like Aloe Vera that can improve the coat of your fish.
Beginners and experts alike can simply add water conditioner to their tap water and neutralize all the nasty stuff.
Preparing water for aquariums has never been easier!
Do you need to use a water conditioner?
I often get asked:
Why can’t I just add straight tap water to my aquarium?
I usually answer this question with another question:
Do you think there are fish living in our municipal water supply?
The answer, no.
And that’s because the water contains so much chlorine that fish can’t live in it.
But don’t just take my word for it…
The US Fish & Wildlife Service states that a pint of chlorine would be all that is needed to poison fish in 20,000 gallons of water (two tanker trucks).
It doesn’t take much chlorine to kill your fish.
Your tap water likely contains more than enough to do the job…
According to the World Health Organization, most drinking water contains concentrations of between 0.2–1 mg per litre of chlorine.
Even on the lower end, that amount of chlorine is lethal to fish.
The Food and Agriculture Organization of the United Nations states that active chlorine concentrations of 0.04 – 0.2 mg per litre are considered toxic to the majority of fish species.
Fish don’t swim in chlorine in their natural environment – so don’t add it to your tank.
Unless you really know what you are doing, I recommend using a water conditioner for tap water.
Why saltwater tanks don’t need water conditioner
Water conditioner should only be used with freshwater aquariums only.
This is because water conditioner does not remove chloramine and heavy metals. Instead it neutralizes them, rendering them harmless to your fish.
The problem here is that they still exist in your water, meaning algae and cyanobacteria can still use them as a food source.
Where possible, I recommend using RO/DI water for salt water aquariums.
RO/DI water not only has heavy metals, chlorine and chloramine, and other nasty stuff as well, but also the good stuff like magnesium and calcium which help buffer your tank (KH) and other trace elements.
Yes, this make straight RO/DI water less suitable for freshwater aquariums. But for a saltwater aquarium, the salt mix adds the good stuff back into the water anyway.
That said, a bottle of water conditioner can be a life-saver in an emergency where you find yourself needing to treat tap water for your tank. I keep a bottle on hand, just in case.
One final word of warning for those of you with protein skimmers – unless a water conditioner specifically states it won’t cause a protein skimmer to foam, I would recommend caution.
When in doubt, assume that your water conditioner is not protein skimmer safe.
How often should you use water conditioner with tap water?
You should use a water conditioner each and every time you perform a water change or top off your freshwater tank.
Simply add the water conditioner to the tap water before you pour it into your aquarium.
If you don’t, you are basically dumping toxic chemicals into your fish tank.
Those of you who are in the process of cycling a new tank will need to add water conditioner every day until your tank has finished cycling.
Different types of water conditioners
At the time of writing this there are four different types of water conditioners commonly used in aquariums.
Instantly removes chlorine but leaves ammonia and heavy metals
Even though Dechlorinators have become less popular because they do not deal with ammonia, you can still find them on pet store shelves. CrystalClear Vanish is one of the more popular brands.
Warning – If your tap water contains chloramine, a dechlorinator can cause ammonia to build up to dangerous levels!
2. Chloramine Neutralizer
Instantly removes chlorine, breaks down chloramine and neutralizes ammonia in one of two different ways:
- Binds the ammonia molecule, causing it to become harmless to your fish
- Converts the ammonia into ammonium, also harmless to your fish.
Fritz Pro is a popular water conditioner that just focuses on chlorine and chloramine without all the extra stuff.
While some brands of chloramine neutralizer will also neutralize heavy metals, others will not – always check the packaging to make sure you are buying the right water conditioner for your situation.
Important note: If you use an ammonia test kit that is not specifically for ammonia (NH3), it can also pick up the harmless ammonium (NH4). This can make the result look dangerously high, even though it isn’t.
3. Complete Conditioner
Generally speaking, when most aquarists mention water conditioner, this is the type they are referring to.
As the name suggests, this water conditioner does it all:
- Eliminates chlorine
- Neutralizes ammonia
- Detoxifies heavy metals
- Eliminates copper
- Buffers pH
- Protects fish slime coats
The number of actions will entirely depend on the brand of complete conditioner.
My personal favorite complete conditioner is Seachem Prime, I use it in all my aquariums and it takes the top spot in my best water conditioner recommendations.
4. RO Water Conditioner
Okay, so technically this isn’t a water conditioner but rather a re-mineralizer. But because both manufacturers and hobbyists refer to it as a water conditioner, I decided to include it here.
Many Reverse Osmosis (RO) systems remove chlorine, chloramine and the other nasties found in tap water.
Because of this, you won’t need to use a water conditioner with RO water.
But RO water also has the good stuff too, like calcium, potassium, sodium and magnesium – trace elements that are essential for a healthy tank.
An RO water conditioner replaces these missing minerals.
However, an RO water conditioner is generally unnecessary in a saltwater tank, as salt mix does the same thing.
Water conditioner and small tanks
A little bit of water conditioner goes a long way.
For smaller tanks, like betta tanks under 20 gallons, it can be difficult to measure out a precise amount with the cap. Often you will only need a couple of drops.
That’s why I use a measuring syringe like this one.
It allows me to accurately measure out even the smallest amount, so I don’t add too much water conditioner to my tank.
Best water conditioner for your aquarium
I was considering making a list of the most popular water conditioners. But when I stopped to think about it, they all do a similar job to varying degrees of success.
But one water conditioner is unrivaled in its ease of use, ability to condition water and value for money. When it comes down to it, I honestly can’t recommend anything else…
The best water conditioner – Seachem Prime
- Long lasting – 500 ml treats up to 5,000 gallons (20,000 Litres)
- Does not affect pH levels
- Removes chlorine, chloramine
- Detoxifies ammonia, nitrates, nitrites
- Detoxifies heavy metals
- Encourages natural slime coat in fish
If you use a water conditioner with your aquarium you are likely nodding along at my top pick – as a water conditioner, Seachem Prime is unbeatable.
Ask any aquarist to recommend a good water conditioner and Seachem Prime will likely be the response.
Not only is Seachem Prime a complete conditioner, but I found that Seachem Prime lasted the longest. It was the most concentrated formula on the market, meaning you don’t need to add as much to your water.
A bottle of Seachem Prime can last years depending on the size of your tank, and with no expiry date, it won’t go off.
Seachem Prime is also protein skimmer-safe.
Seachem also makes a similar water conditioner designed just for reef tanks, Aqua Vitro Alpha. While you can find it online occasionally, it is typically only stocked by local fish stores. While I recommend using RO/DI water for your reef tank, I keep a bottle on hand in case of emergency.
Seachem Prime really is the ultimate aquarium water conditioner!
Seachem Prime Instructions (click to expand)
When used correctly, water conditioner is an effective way to make your tap water aquarium safe.
Water conditioner has become an essential part of my water changing routine.
One final word of warning before I leave: some brands of water conditioner smell like rotten eggs (sulfur). This is completely normal. Just do what I do and hold your breath when you measure it into the water.
Do you use a water conditioner for your aquarium? Let me know in the comments below