The short answer
Aquarium salt can be a useful occasional tool for certain conditions, but it is not right for every fish or plant and shouldn’t be added routinely to a general freshwater tank. Many plants, and some scaleless fish and invertebrates, react badly to it. The honest answer for most keepers is: you usually don’t need it, and clean, stable water does far more good — so use salt cautiously and deliberately, not by default.
When salt is sometimes used
Aquarium salt (not table salt or marine salt) is sometimes used as a targeted, short-term aid for specific issues in certain fish. Some keepers use it to support fish through particular ailments or stress. But whether it helps, at what strength, and for how long depends entirely on the condition and the species — so it should be a considered decision, not a habit.
When to be cautious or avoid it
Take real care with salt if you keep:
- Live plants — many are damaged by salt.
- Scaleless fish (like some catfish and loaches) — often salt-sensitive.
- Shrimp and snails — invertebrates can be very sensitive.
In a planted or mixed community tank, salt can easily do more harm than good. Always research your specific fish and plants before adding any.
The safer default
For the vast majority of freshwater tanks, the priority is a cycled tank, clean water and low stress — not additives. If you’re considering salt for a suspected illness, check your water first and consult a vet or experienced fishkeeper about whether it’s appropriate for your species and condition. This is general guidance, not a diagnosis or dosing recommendation. See also how do I prevent fish disease?