This does look like ich, a common but problematic parasite. Is he behaving any differently? Rubbing against rocks or plants? Ich will cause skin irritation that fish will try to relieve by scratching their skin. I’ve had some success treating ich in my tanks with increased temperature. Ich can’t reproduce in temperatures above 86 degrees Fahrenheit so you can break the cycle that way. They also make ich medications, but depending on the size of the tank, that could be very expensive and will dye the sides of the tank. What fish are in the tank? That will help determine the best treatment.
Regardless of treatment (medicine or heat), there are a couple things to remember:
1. Heat and medication both reduce the dissolved oxygen in the tank, so be contentious if oxygenation. One way to combat this is to increase surface agitation. This can be done with air stones, aiming a water pump more toward the surface, or lowering the water level so the return from the filter (assuming a hang-off-back filter) will create more of a splash. Frequent water changes will also help with this, as well as help clean the infested water.
2. Ich is a parasite with a multi-phase life cycle. The white spots are the adult stage which are immune to treatment, and will fall off in order to reproduce. Often, this can be confused with having cured the ich, and people will sometimes stop medicating. It is important to medicate until there is no sign of ich for at least 5 days.
Good luck!
