A tank that has gone cloudy, or a fish showing the first fuzzy patches of fungus, rarely gives much warning, and salt is one of the oldest and cheapest responses a fishkeeper has.

This is Supa's tonic salt, used as a mild conditioner and antiseptic in freshwater aquariums, sold in a resealable tub to keep the salt from picking up moisture between uses. Supa give three separate dilution guides depending on the job: general water conditioning, an active outbreak, and hatching brine shrimp eggs.

• Mild conditioner and antiseptic for freshwater aquariums
• Water conditioning: 1 teaspoon per 18 litres
• Outbreak dilution: 1 teaspoon per 5 litres, rising to 2 teaspoons per 5 litres on day two
• Brine shrimp hatching: 6 teaspoons per 5 litres
• Resealable tub, 250G

On the numbers. Supa's own directions are dilution by teaspoon rather than a precise weight, so measuring is only as accurate as the teaspoon used, and the outbreak dose is meant to be changed daily rather than dosed once and left. This is a general aquarium salt, not a targeted medicine for a specific fish illness.

Who it's for: freshwater aquarium keepers wanting a general-purpose salt for routine water conditioning, tackling an active outbreak, or hatching brine shrimp eggs, all from one tub.