This question isn’t as easy to answer as you’d expect. Of course white spot ( Ichthyophthirius multifiliis ) is visible on the fish with the naked eye. But unfortunately there is a similar looking disease against which the white spot disease remedy is powerless: the velvet disease ( Oodinium ). White spot disease is caused by ciliates (single-cell organisms with cilia to propel them), which – along with many other single-cell organisms – can be safely and easily killed off with the remedy JBL Punktol Plus 125 . But Oodinium is a dinoflagellate (a kind of algae) which can ONLY safely be killed by means of copper (copper content 0.3 mg/l; with JBL Test Cu Cuivre ) . For example, the remedy JBL Oodinol Plus 250 contains copper and is therefore effective against Oodinium. JBL Punktol Plus 125 against white spots does NOT contain any copper!
But if you misdiagnose it, and it is velvet disease, not white spot disease, using the white spot remedy will have no effect. All your fish could die before you even notice your mistake. It is better the other way round: if the fish have white spots, but are misdiagnosed and treated for Oodinium, the active substance will also treat the white spots. It won’t work as well as the white spot remedy, JBL Punktol Plus 125 , but it will work. The main drawback is that not all aquarium dwellers tolerate copper. For shrimps and other invertebrates copper, even in its smallest measurable amounts, is lethal. Using JBL Punktol, therefore, is not only the more congenial, but also the more effective solution!
A glance through a microscope with a mere 400-fold enlargement would settle the matter. The white spot pathogens are quite large ciliates, which move actively and often have a clearly visible nucleus. Ideally the hoof-shaped nucleus needs to be seen in side view . If the ciliate turns the nucleus can become line-shaped (a rotated horseshoe) . Typically the ciliate itself is round in shape.
Oodinium, the pathogen of the velvet disease, is more oval in shape and often has a visible “polar cap” and is nowhere near as agile as the Ichthyo parasite. It is also significantly smaller and doesn’t have a clearly visible nucleus, as the white spot ciliate does.
So using a microscope can really be a great help when distinguishing between these two diseases to reach the right diagnosis. Because even though these diseases show up differently in appearance on the fish, these differences are not so easily visible to the naked eye. Young Ichthyo pathogens can look like velvet disease and several Ichthyo pathogens in one place look like a fat Ichthyo spot.
Use the benefits of a simple microscope to make a reliable diagnosis!