Ich (white spot)

White spots that look like salt on fins and body are usually ich (Ichthyophthirius multifiliis). It spreads. The free-swimming stage is what medication hits. The spots you see are already under the skin.

What it looks like

• Tiny white grains on body and fins, not a few large lumps
• Flashing — rubbing on décor
• Clamped fins, hiding, appetite gone when it gets heavy

Not every white mark is ich. Lymphocystis is cauliflower lumps. Epistylis looks fuzzier. Wounds are wounds. If you are unsure and fish are flashing, treat as ich anyway — waiting is how you lose a school.

Why it showed up this week

Ich rides in on new fish and explodes when something stresses them: a cold bag, a 10-degree swing, ammonia, bullying. The parasite was often already in the tank at a level you could not see.

Quarantine is how you stop bringing it into a display. QT basics. Slow acclimation is not quarantine, but dumping a cold bag into 78°F water is how you start this page.

Treatment that actually finishes

1. Confirm the livestock. Warm-water protocols are not for fancy goldfish. Shrimp and snails hate copper. Scaleless fish (corys, loaches) are sensitive to a lot of bottles.
2. Raise temperature slowly toward the upper end for those species — often 78–80°F for tropicals — to speed the life cycle. More air: warm water holds less oxygen. Filter outflow at the surface, or an airstone.
3. Medicate the whole tank (or the hospital tank the fish are in). Stopping when spots vanish leaves tomites in the water. Finish the label course.
4. Pull carbon while you medicate. Carbon eats the medicine.
5. Do not treat one fish in a cup and leave the display. The tank is infected.

Follow the bottle. Malachite green blends, some ich-X type products, copper — they are not interchangeable with inverts. If the display has shrimp you care about, hospital the fish and accept that the display may still need a fallow period.

Salt can support some freshwater treatments. It is not a guaranteed solo cure, and it is a bad idea with plants and scaleless fish if you dump it.

What not to do

• Huge water changes mid-course without redosing
• Stacking three medications because the spots are ugly
• Turning the heater to 86°F on goldfish
• “It cleared, so I stopped on day three”

After it is gone

Keep temperature stable. Do not add more fish for a couple of weeks. Watch for a rebound. If ammonia crept up because you stopped water changes during treatment, start measured changes again: water change calculator.

Healthy tanks still get ich. Fast treatment beats shame. The boring prevention is QT, not another bottle of “stress coat.”