API aquarium salt for freshwater fish
Regular price
$59.00
Regular price
Sale price
$59.00
Unit price
/
per
| Packaging | Price | Price per kg | vs 453 g |
|---|---|---|---|
| 936 g | $59.00 | $63.03 | −44 % |
| 453 g | $51.00 | $112.58 | — |
| 22.67 kg | $292.00 | $12.88 | −89 % |
$19.66 × 3 with no fees
Klarna.
This salt, made from evaporated sea water, is added to a freshwater aquarium at start-up and at every water change, at a rate of one heaped tablespoon per 20 litres of replacement water. Some live plants are sensitive to it.
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The summary
- The dose: one heaped tablespoon per 20 litres, or half a teaspoon per 4 litres.
- When to add it: when filling the tank, at every water change, and during recovery from illness.
- What you need to know: salt does not evaporate and filtration does not remove it.
- Salt or targeted treatment: salt supports water maintenance, while a treatment is for a fish that breathes poorly or is losing weight.
- With live plants: some plants are sensitive to it.
- Shipping: by tracked parcel from France, which can be combined with the rest of your order.
Evaporated sea salt for freshwater aquariums, to be dosed at water changes
API aquarium salt for freshwater fish is a water conditioner made from evaporated seawater, to be added when filling the tank and at every water change. The dose is one heaped tablespoon per 20 litres, calculated on the volume replaced only. Salt does not evaporate and filtration does not remove it, which is why it is dosed this way.
This salt comes from evaporated sea water, and it is used in a freshwater aquarium. It provides electrolytes, which improve the fish's respiration by acting on how their gills function and by reducing their stress. The dose is one heaped tablespoon per 20 litres, or half a heaped teaspoon per 4 litres if your volume is small.
🐟 Salt and gills
A freshwater fish lives in water far less salty than its own blood. It therefore constantly maintains the balance of the electrolytes in its internal fluids, that is, the dissolved mineral salts that conduct electricity. These electrolytes play a part in the exchanges that take place through the gills: the uptake of oxygen, and the release of carbon dioxide and ammonia. When they are lacking, these exchanges work less well, which is why a salt supplement accompanies the moments when your fish are under the most strain, such as filling a new tank or a large water change.
🔁 The salt stays in the tank
Salt does not evaporate and is not removed by filtration, and it is this fact that determines how you dose it. A level that drops by 3 cm through evaporation represents a loss of water, not of salt: topping up the level from the tap therefore requires no addition. On the other hand, the water you remove during a water change carries its share of salt away, and it is that volume, and that volume alone, that you re-dose. The two actions look alike, but only the second keeps the concentration stable, whereas adding salt with every top-up makes it rise from week to week.
Count the volume changed, not the volume of the tank
Re-dosing on the total volume at every water change makes the concentration rise week after week. In a 200-litre tank where you replace 40 litres, the dose is calculated on 40 litres. Dissolve the salt in a separate bucket of water before pouring it in, rather than dropping it into the tank as crystals. And bear in mind that some live plants are sensitive to it.
Monitoring nitrite during a refill
After filling a tank or a large water change, the nitrite drop test is the one to keep beside this salt. It shows whether the bacterial colony in the filter is properly converting the fish waste, something no addition of salt can replace. In a few minutes, you know whether the tank is ready to receive new fish.
This salt changes neither the hardness of the water nor its pH, so your settings stay the ones you know. If you are treating the tank at the same time, pour in the treatment or supplement first into the fresh water, then the salt. In a 100-litre tank, one heaped tablespoon per 20 litres means 5 spoonfuls when first filling, then one spoonful for every 20 litres replaced at each maintenance.
🧂 The three times to use it
Salt is added on three occasions, and no others. At start-up, it is dosed for the full volume of the tank; after that, it is only topped up for the water that has been replaced. It also supports the recovery of a sick fish, particularly in the case of an infestation by skin or gill parasites, alongside the appropriate treatment and not instead of it. For a fungal disease, it is not enough and serves only as support for the medication.
When filling with water
Add the salt when setting up a freshwater aquarium, before the fish arrive.
At water changes
Dose according to the volume replaced, each time you remove some.
Recovering
Salt supports the treatment of a sick fish, at the same dose.
🌿 Planted tank and aquaponics
Some live plants are sensitive to salt, so caution is called for in a planted aquarium. In an aquaponic system the question is different, because the whole circuit feeds crops and sodium, which does not evaporate, builds up there with every addition. If you need to treat a fish, move it to a separate quarantine tank, where the salt can be dosed without affecting the plants or the system's water. The guide to fish to raise in aquaponics will help you choose species suited to your set-up.
🪣 Which pack size to choose
Three pack sizes are available, and the choice depends on how often you change your water rather than the volume of your tank. The 936 g size treats about 830 litres of water. For a living-room tank in which you replace 20 litres a week, you use one heaped tablespoon each time, and this size then covers around forty water changes, or more than 9 months of maintenance.
The 453 g size suits a small tank or a first trial, while the 22.67 kg bucket is aimed at an installation with several tanks, a breeding operation or a shop. Whatever the size, keep the salt dry and tightly closed, and take it out with a clean spoon so as not to introduce anything into the tank. Throughout the period of use, also keep an eye on your water readings, and in particular on nitrite, which salt does not bring down: a tank where it appears needs bacteria and time.
Technical specifications
The essentials
- Dose
- 1 heaped tablespoon per 20 LOr one heaped half teaspoon for 4 litres.
- Origin
- Evaporated seawater
When to add it
- The three stages
- Filling, water change, recovery
- For what volume
- On the volume replacedSalt does not evaporate and filtration does not remove it.
Precautions
- Live plants
- Handle with careSome plants are sensitive to it.
- Hardness and pH
- UnchangedSalt has no effect on general hardness or on the pH of the water.
To budget for separately
- Dissolving bucket
- A clean bucket kept just for the tub
- Water monitoring
- A nitrite test
In the box
- 1 pack of 453 g, 936 g or 22.67 kg depending on the size chosen
Dose, composition, yield and warnings taken on 11/10/2026 from the API Aquarium Salt data sheet and packaging.
Two bottles for two different situations
This salt goes with water that is being refreshed. The other product is for a fish that is unwell.
Routine maintenance, or a fish that worries you
Both products are poured into the tank water. They do not answer the same question.
| What the product is aimed at | For a fish that breathes poorly or is losing weight | For a tank that is starting up or having its water changed | Directions for use | Can be given in the food | Added with every water change | Be careful with live plants | Activated carbon to be removed during use | Price | |
|---|---|---|---|---|---|---|---|---|---|
| Preis Carely gill and intestinal care forYour choice | The fish's gills and intestine | Yes | No | 15 ml per 100 L on days 1, 2, 8 and 9 | Yes | No | No | Yes | $33.00 |
| Recommended API aquarium salt for freshwater fishYour choice | Adding electrolytes to the water | No | Yes | 1 heaped tablespoon per 20 L | No | Yes | Yes | No | $51.00 |
Preis Carely gill and intestinal care for
What brings you here
What the product is aimed atThe fish's gills and intestine
For a fish that breathes poorly or is losing weightYes
For a tank that is starting up or having its water changedNo
Use
Directions for use15 ml per 100 L on days 1, 2, 8 and 9
Can be given in the foodYes
Added with every water changeNo
What you need to know
Be careful with live plantsNo
Activated carbon to be removed during useYes
In the shop
API aquarium salt for freshwater fishRecommended
What brings you here
What the product is aimed atAdding electrolytes to the water
For a fish that breathes poorly or is losing weightNo
For a tank that is starting up or having its water changedYes
Use
Directions for use1 heaped tablespoon per 20 L
Can be given in the foodNo
Added with every water changeYes
What you need to know
Be careful with live plantsYes
Activated carbon to be removed during useNo
In the shop
Protocols, compositions and warnings recorded on 20 September 2026 from the Preis-Aquaristik instruction leaflet and from the product sheet on the official API Fishcare website.
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Dispatched as a tracked parcel from France, and can be combined with the rest of your order. The exact charges and delivery times are shown at the basket once the address has been entered. Outside the European Union, import duties and taxes are payable by the recipient.
Frequently asked questions
8 questions
6 key questions, 8 in the detailed view
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