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Review - Water Conditioners and Dechlorinators

There is a wide range of products available for 'conditioning' water to make it safe for aquarium use. Not all of these products do quite the same job, and in some cases the details on the packaging are a bit vague. This can lead to confusion when attempting to chose the right conditioner to suit your needs. Below is a summary table of the major brands available, along with some more detailed notes about their uses and limitations. This information should allow you to quickly compare the products available, and decide which best fits your requirements. See the manufacturers pages for the full information available - the amount of detail provided varies somewhat between manufacturers!

This review covers products intended for use in dechlorinating water, binding heavy metals, and providing a protective coat to fishes' scales - it does not cover bacterial starter products, which will be the subject of a separate review.

There are also a number of products which are designed as a slime coat protector only. As they are not dechlorinators, they have been omitted from the main table for clarity, but are included in the summary table of recommendations below. There are also products which are marketed as emergency ammonia removers, but which can also remove chlorine and chloramine, and have therefore been included in the main summary table.

Summary of Water Conditioner Products
Product and
Deals with chlorine/ chloramine?Binds heavy metals?Slime coat protector?Contents (where specified)
and links to manufacturers info
API Ammo LockY/YNN
API Stress CoatY/(Y)*YAloe VeraSodium thiosulfate, Aloe Vera
API Tap Water ConditionerY/NYN
AquaScience UltimateY/YYYBuffer system, dechloraminating agent, physiologically active electrolytes, tertiary polymer system, stabilizers
Hagen/Nutrafin AquaplusY/(Y)*YPure Herbal Extract
Kent Ammonia DetoxY/YNNContains Hydrosulfites
Kent ChlorinexY/NYNDeionized water, sodium thiosulfate, stabilizers.
Kent Pro Tech Coat FreshwaterY/NYPolyvinylpyrrolidone (PVP)Deionized water, polyvinylpyrrolidone, sodium thiosulfate, inorganic stabilizers, preservatives.
Kordon AmquelY/YNNSodium hydroxymethanesulfonate
Kordon NovaquaY/(Y)*YSynthetic colloidUnique combination of chemical compounds and inorganic salts
Marineland BIO-SafeY/YNNSodium hydroxymethane sulfinic acid
Seachem AmGuardY/YNN
Seachem ChlorGuardY/NNN
Seachem PrimeY/YYYContains complexed hydrosulfite salts
Tetra AquaSafeY/YYYSodium Hydroxymethane Sulfinate, Polyvinyl Pyrollidones, Organic Hydrocolloids, Organic Chelating Compounds.
Waterlife HaloexY/(Y)*YAloe Vera

* Note: Products where the second "Y" is in brackets are those which state that they remove chloramine, but in most cases contain only sodium thiosulfate (the same as standard dechlorinators for chlorine only). Usually, a higher dose is recommended for chloramines - this is to make sure the chlorine part is split from the chloramine and neutralised - however, this releases the ammonia part, so the chloramine is not fully dealt with. An example of the manufacturers' awareness of this, is shown by the fact that API recommend Ammo-Lock in conjunction with Stress Coat, if you need to deal with ammonia.

In cases where the ingredients are not stated for standard dechlorinators, it is highly likely that the dechlorinator is sodium thiosulfate.

Additional manufacturer's comments

The quotes below have been included because they are relavant to the other notes and discussion on this page.

API Stress Coat
"If you need to detoxify ammonia use Ammo-Lock 2."
"Protein skimmers should be turned off for at least one hour after adding Stress Coat in order to prevent excessive foaming."

Kent Pro Tech Coat Freshwater
"Pro Tech Coat Freshwater is different than competing products because it contains only costly polyvinylpyrrolidone as the coating ingredient. This same product is FDA approved as an ingredient in human medicinal and nutrition products. Competing products contain cheap fillers such as aloe vera and carboxymethylcellulose which then decay in the aquarium and lower the redox and the overall water quality."

Seachem Prime
"Converts ammonia to non-toxic form which can be removed by biofilter. Can be used to alleviate ammonia/nitrite stress in cycling tank. For exceptionally high chloramine concentrations, a double dose may be used safely. To detoxify nitrite in an emergency, up to 5 times normal dose may be used. If temperature is > 86 F (30 C) and chlorine or ammonia levels are low, use a half dose. Prime(tm) will not over-activate skimmers."

Tetra AquaSafe
"AquaSafe will not remove ammonia from an uncycled, overstocked, or underfiltered aquarium."

Summary: Recommendations for use*
If you need a conditioner for...Consider...
Economical removal of chlorine only
(API Tap Water Conditioner and Kent Chlorinex also bind heavy metals)
API Tap Water Conditioner
Kent Chlorinex
Seachem ChlorGuard
Wardley Chlor Out
Removal of chlorine, heavy metals and slime coat protectorAPI Stress Coat
Hagen/Nutrafin Aquaplus
Kent Pro Tech Coat FW
Kordon Novaqua
Waterlife Haloex
Complete removal of chlorine, chloramine and ammonia only (no other additives)API Ammo-Lock
Kent Ammonia Detox
Kordon Amquel
Marineland BIO-Safe
Seachem AmGuard
Complete removal of chlorine, chloramine and ammonia, heavy metals and slime coat protectorAquaScience Ultimate
Seachem Prime
Tetra AquaSafe
Protection against ammonia in a cycling tankAPI Ammo-Lock
AquaScience Ultimate
Kent Ammonia Detox
Kordon Amquel
Seachem Prime or AmGuard
Slime coat protection onlyMarineland BIO-Coat
Seachem StressGuard
* Note that the recommendations for use are a guide based on the information available from manufacturers. If you have any concerns about the suitability of a particular conditioner for your needs, you should contact the manufacturer directly.

Question: Do I need a slime coat protector in my water conditioner?

This is an area which has been the subject of some controversy on the net and elswhere, and note that the conditioners detailed above do not all contain the same type of slime coat protector, so the issues raised may or may not apply to specific conditioners. The main questions raised are:
- can they be harmful?
- do they actually work?
- even if they do, do I need them?

One of the main reasons for the first question above is the concept that anything which sticks to the body tissues of fishes might also stick to the gill tissue and inhibit the function of the gills, or even suffocate the fish. I do not know of any definitive evidence to support this claim, and some claim the complete opposite - that substances like aloe vera do not adhere to fishes in water in any case, and therefore do nothing.

Another controversial question originates from the suggestion by some manufacturers that their product stimulates the fish to increase its own slime coat, rather than providing an artificial one. This might be taken to mean that the mechanism is to cause irritation to the fish, like a parasite might for instance, hence stimulating the fish to produce more of its natural slime coat. These claims are vigorously supported or denied, depending on who's opinion you are hearing.

Widespread use of the products would suggest that they cannot be harmful in any obvious way, and some manufacturers claim to have data to demonstrate that these products work (but no references or links to papers published in peer-reviewed journals unfortunately). So if we assume the products are harmless and can protect a damaged area and/or promote healing, should we be adding them at every water change? If you have a tank full of healthy fish, this is certainly debatable.

The whole basis of these additives is that fish are protected by a slime coat, which a healthy fish can produce without assistance! If you have faith that they help when fish are injured or 'stressed' (a vague term often mis-used by manufacturers), then by all means use them when that situation arises. If no problem is evident, then many people take the approach that you should not add any unnecessary chemical or other substance to your aquarium, which there is not a clear need for (an approach I certainly agree with).

One of the important reasons for this approach is that it is difficult to assess the interaction of different elements within a dynamic system like an aquarium. But if adding them "won't cause any harm", then isn't it "better" to just add them in any case? Are there any disadvantages?

Note Kent's comments above with respect to PVP vs Aloe Vera. There is some truth to those statements, in that substances like aloe vera are certainly adding to the organic waste load in a tank (note API's comment that protein skimmers should be turned off for at least an hour after adding Stress Coat, to prevent excessive foaming). Given that protein skimmers, activated carbon and water changes are all means employed to reduce organic load in the aquarium, there is certainly an argument for not adding more, unless it is strictly necessary.

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