Generally with no notable signs of parasites and the fact that its scratching suggests flukes. With flukes other symptoms you may notice is rapid breathing, fish acting lethargic or swimming near the water surface, hiding in the corner of tank or behind rocks, loss of appetite, shaking its head, flashing/darting, develop clamped fins, , or scratching against objects. They may also exhibit what looks like yawning from gill irritation develop, cloudy eyes and loss of color.
Often, you can offer a freshwater dip for 5 mins in tap water the same temperature as display tank. This will dislodge flukes if any and offer temporary relief. Assure the container used is Clean and after returning fish to tank, look on bottom of container for what looks like fish scales or sesame seeds. Those will be fluke worms. You may need a flashlight to best see them.
You can do prazi as a precaution assuming its flukes. To be safe , dose at 80% of recommended and allow it to do its thing for 8 days, do a water change and do one more 8 day dose interval
Use airstone with prazi as it does reduce both oxygen and appetite
