Best Aquarium Water Conditioner (Review & Buying Guide) in 2018

If you’re filling your fish tank with tap or well water, using a water conditioner is a must. Tap water contains chemicals which, although they’re safe for humans, can be harmful to your fish. Using a water conditioner is a simple and effective way to keep your fish happy and healthy in their home. They’re easy, fast, and safe for your fish – not to mention being highly cost-effective. These conditioners work through a series of chemical reactions which remove harmful substances from the water, or convert them into something safe.

With so many water conditioners out there, though, knowing which one to choose can be tough. We’ve searched the market to track down the best aquarium water conditioner available. We’ve also answered some common questions about how these conditioners work, how to find the best product for you, and how to properly use them. We hope this buying guide helps you provide your scaly family members with the healthiest home possible.

Best Aquarium Water Conditioner Buying Guide & FAQ

And there you have it – our top 10 water conditioners. Hopefully among the list you’ll find the one that’s right for your aquarium. With so many to choose from, though, we know it can be difficult to pick the right conditioner for you – that’s why we’ve addressed some common questions and concerns about these products below. If you’ve ever wondered exactly what chloramine is, or why tap water conditioner is so vital, read on!

aquarium conditioner

What to Consider When Buying Aquarium Water Conditioner

Which water conditioner you choose will be a combination of factors; below we outline some of the most significant.

  • Aquarium or Pond?

Water conditioners are usually tailored to use with either an aquarium or a pond, since these two environments are very different. For one thing, since ponds typically contain a larger volume of water than aquariums, they require a larger dose of conditioner. For this reason, pond water conditioners tend to be more highly concentrated than their aquarium use counterparts. Ponds’ large surface areas also means that some chlorine is naturally liberated from the water through evaporation. Because of this, pond water conditioners sometimes contain smaller doses of de-chlorination chemicals.

  • Salt or Fresh Water?

Many water conditioners are suitable for use with both fresh and salt water, but not all of them. Always check the manufacturer’s guidance to see whether the conditioner is suitable for the type of water you’re working with.

  • Do you need a Stress Coat?

Some water conditioners contain what’s known as a stress coat. This consists of ingredients which either provide or promote the fish’s natural protective slime coat. With proper care, fish are usually very good at maintaining their slime coats without help. However, if a fish becomes injured or sick, using a product which promotes a healthy coat can aid the healing process. For fish in a new tank, using a stress coat can also be a good idea. It will help to protect them against bumps and scrapes whilst they adjust to their new environment.

  • What chemicals does it work with?

Some conditioners, usually those marketed as ‘complete’, remove virtually every potentially harmful substance: chlorine, chloramine, ammonia, nitrites, nitrates, and heavy metals. Not all conditioners do this, however. When setting up a new tank, using a complete conditioner is a good idea, but beyond this stage – assuming the aquarium is properly maintained – chlorine and chloramine are the biggest issues to address. When choosing a conditioner, check the manufacturer’s recommendations, as it may need to be teamed with another product to offer full water care.

Benefits of Using Aquarium Water Conditioner

There are many reasons that aquarium and pond owners alike choose to use a water conditioner. Below are some of the most important.

  • Water conditioners make tap water safe for fish to live in – this means you don’t need to find an alternative water source
  • Water conditioners are easy to use
  • Water conditioners are a cost-effective way to maintain optimum water qualities
  • Conditioners remove chloramine and ammonia from water
  • They can support your fish’s natural slime coat
  • Some conditioners support good bacteria in the water – much like a pro-biotic
  • Keeping a fish’s water in good condition will lead to longer, healthier lives for your pets
  • Most conditioners will not impact the pH of your pond or tank

Chlorine and Chloramine

Most of us have heard of chlorine – the sharp-smelling gas which is used to kill bacteria in both swimming pools and tap water – but chloramine is perhaps a less familiar name.

Chloramine, as its name suggests, is a derivative of chlorine and ammonia. It forms when a chlorine atom replaces a hydrogen atom in a molecule of ammonia. Chloramine is sometimes added to tap water as a disinfectant, since it is less potent and more stable than chlorine. Where chloramine is not added to tap water, it can still from in an aquarium or pond. This happens when ammonia in the water, which is produced by fish as a waste product, reacts with dissolved chlorine gas:

2 NH3(g) + Cl2(g) ⇌ NH2Cl(g) + NH4Cl(s)

In small doses, chlorine and chloramine are perfectly safe for humans, but for fish these same doses can be harmful, because of their much smaller body sizes and the sensitivity of their gills. Chlorine dissolved in water can produce chemical burns on fish’s gills, preventing them from properly absorbing the oxygen they need to survive. The chemical can also be absorbed into a fish’s body, and cause further burns internally. Even very low doses cause irritation which will be stressful and impede the fish’s quality of life.

Chloramine can also inflict severe damage on fish. When absorbed into the bloodstream, it reacts with hemoglobin (the substance responsible for carrying oxygen round the body), and transforms it into methemoglobin. Methemoglobin is far less efficient at carrying oxygen, so this process can result in the fish struggling to maintain oxygen levels. Fish suffering from chloramine damage will often gasp for breath at the surface of their tank or pond. Both chlorine and chloramine also kill bacteria indiscriminately – this means they kill off the helpful bacteria which break down waste products in a normal aquatic environment, leading to a buildup of ammonia and nitrites.


Q:  What is an aquarium water conditioner?

A:  An aquarium water conditioner is a formula which is added to tap water to make it safe for fish to live in. The chemicals used to kill bacteria in our tap water – chlorine and chloramine – are dangerous for fish, so must be removed. Certain conditioners also remove waste products which naturally from in an aquatic environment but can be harmful, such as ammonia, nitrites, and nitrates.

Q:  How does aquarium water conditioner work?

A:  Water conditioners work through a number of chemical reactions which remove chlorine, and transform chloramine and waste substances into less harmful ones. Chlorine is removed in a chemical reaction known as reduction – ingredients such as sodium thiosulfate convert harmful chlorine atoms into harmless chloride ions (Cl-). The same type of reaction breaks down the bonds between the chlorine and nitrogen atoms in a molecule of chloramine. The chlorine atom is replaced with a hydrogen atom, forming ammonia, which is much less harmful, and usually processed into even less harmful ammonium by helpful bacteria in the tank. Some conditioners remove ammonia too, by converting it into ammonium as the bacteria would. This process involves adding an additional hydrogen atom to an ammoia molecule, transforming it from NH3 to NH4.

Q:  When to add water conditioner to the aquarium?

A:  When you first set up an aquarium or pond using tap water, you should add a complete water conditioner before introducing the fish to their new home. You will also need to add water conditioner whenever you top up or replace the water in the tank. Always check the manufacturer’s instructions for advice about how the conditioner should be used.

Q:  How much water conditioner to use in fish tank?

A:  The amount of conditioner you need to use will depend upon the size of the tank and the concentration of the conditioner. Most conditioners will recommend a dose per gallon of water – usually three to five drops – so always check the label before use.

Q:  How often to use water conditioner in the aquarium?

A:  Each manufacturer will have slightly different recommendations about how often to use their product, but generally speaking it should be used when a new aquarium or pond is set up, and whenever the water is topped up or replaced. Experts recommend changing 10 -15 per cent of a tank’s water every week; this means in most cases the appropriate amount of conditioner should be added to the water on a weekly basis.

aquarium conditioners

Our Top Pick

Having searched the market, we believe that the best aquarium water conditioner has to be SeaChem’s Prime formula. Not only does it offer fish complete protection against most substances in tap water which can be toxic to fish, it also protects fish’s natural slime coats, helping them stay healthy and happy.

Prime offers all of these benefits without affecting the water’s pH, and is diverse enough to be used in both fresh and salt water. Overall, we believe that SeaChem’s offering provides aquarium enthusiasts with a highly effective – not to mention easy – way to maintain the best quality water for their fishy friends.