What's it look like when he goes to the toilet, look at the anus does it look enlarged and inflamed, here is abit of info on leeches but i'm not the author of it.
Leeches
Symptoms:
Infected fish can be seen with worm-like organisms up to 2 inches, which firmly attach to the skin, fins, or gills. Red lesions or sucker marks may even be present.
Cause:
Leeches. Leeches feed on flesh and blood and can cause significant damage if they are not dealt with swiftly. Leeches often carry various bacterial and parasitic illnesses; therefore, secondary infections may follow. Leeches are usually introduced into the aquarium via live foods and plants.
Treatment:
The most effective medications are Fluke-Tabs, Clout, Paragon and Trifon. Salt dips are also very effective. Removing live Leeches from fish is not advisable considering how strongly they adhere to the body of the fish. Attempting to remove them may cause significant pain to the fish as well as physical damage. The lesions caused by the parasites should be treated to prevent secondary infection as well as aid in healing. Carefully dab the wounds with Methylene Blue. If you suspect that your fish may have a secondary bacterial infection, it is highly recommended to supplement treatment with a medicated antibacterial food.
