Seachem
Seachem Prime Water Conditioner
A concentrated water conditioner. The manufacturer states it treats ammonia, nitrite and nitrate, and that a 500 mL bottle covers 50,000 gallons.
View on AmazonLast updated: 2026-04-10
How we researched this: we compared the manufacturer's specifications and label claims, published guidance and reported owner experience. We have not tested this product ourselves, and nothing here is veterinary advice. Editorial policy
Strengths
- Maker says it binds ammonia
- Highly concentrated
- Maker: 500 mL treats 50,000 gal
- Dechlorinates tap water
Drawbacks
- Strong sulfur smell
- Difficult to dose small amounts
- Confusing instructions
Seachem Prime Water Conditioner: In-Depth Research
Editorial analysis by the FurReviews team, based on manufacturer specifications, published guidance and reported owner experience. We have not tested this product ourselves.
What a water conditioner has to do
Tap water is treated to be safe for people, and the things that make it safe for people are harmful to fish.
Chlorine damages gills and kills the nitrifying bacteria in your filter. It does gas off over a day or two if water is left standing.
Chloramine is chlorine bonded to ammonia, and it is increasingly what water companies use instead, because it is more stable in the pipes. That stability is the problem: chloramine does not gas off, so leaving water standing overnight does nothing. It must be chemically broken.
When a conditioner breaks chloramine, it releases the ammonia that was bound in it. A conditioner that only removes chlorine leaves that ammonia free in your tank. That is the reason to use a product that also binds ammonia, and it is the main functional difference between a basic dechlorinator and a comprehensive one.
Check with your water supplier which they use. It changes what you need.
Concentration, and dosing carefully
Highly concentrated conditioners are economical and easy to overdose, which is the practical trade-off.
The ammonia claim, read correctly
Products that "detoxify" ammonia and nitrite do not remove them. They bind them into a form described as non-toxic and still available to your biological filter.
Three consequences:
Using it properly on a water change
When a conditioner is not the answer
Storage and shelf life
Keep the bottle closed, cool and out of sunlight. These products have a sulphur smell that intensifies with age and is not in itself a sign of failure, though a bottle that has been open for years is worth replacing.
Write the opening date on the bottle. A conditioner that has quietly stopped working is an invisible problem.
Who should look elsewhere
If your supply is chlorinated rather than chloramined, a basic dechlorinator does the essential job for less. If you have persistent ammonia, the answer is water changes and finding the cause, not more conditioner. And if you are cycling a tank, buy a liquid test kit before buying anything else.
Seachem Prime Water Conditioner: Common Questions
Do I need a water conditioner for tap water?
Yes. Chlorine damages gills and kills filter bacteria, and chloramine — increasingly what suppliers use — does not gas off at all, so leaving water standing overnight does nothing. Chloramine must be chemically broken, and breaking it releases the ammonia it contained, which is why a conditioner that also binds ammonia matters.
Does it actually remove ammonia?
No — it binds it into a form described as non-toxic and still available to your filter bacteria, typically for around a day or two. It is a bridge during a cycle, an emergency or a filter failure. The actual fix is water changes and a functioning biological filter.
Why does my ammonia test still read positive after dosing?
Because standard liquid test kits measure total ammonia, bound and free alike. A reading after dosing cannot tell you which you have. Judge by the fish and by the trend over several days rather than chasing a number you have just dosed against.
Can I overdose a concentrated conditioner?
Yes, and concentration is exactly why care matters — a few millilitres treats a large volume. Measure with the cap graduations or a syringe, and dose against your actual water volume, which is ten to fifteen per cent below the tank's nominal size once the rim gap, substrate and decor are accounted for.
Can I rinse my filter media in tap water?
Never. Chlorine and chloramine kill the nitrifying bacteria you spent weeks growing, and rinsing media under the tap is the most common way people accidentally restart a cycle in an established tank. Rinse it in water you have just siphoned out of the tank.
Where to Buy
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