Sounds funny to mention constipation in fish but it's not. Its not that uncommon and if left untreated can lead to death.
Symptoms are no apitite, and swelling of the abdomen.
Usually caused by feeding too much protein and hard-to-digest matter. caused by feeding too much protein and hard-to-digest matter to a fish. Bloodworms are notorious for causing constipation.
Treatment
One of the best cures for constipation is to feed peas just shell them and drop them in. If your fish won't eat them you can administer epsom salts in the amount of 1tbl per 5gal this should get things moving again.
Once all is back to normal change the diet to include more veggies and less protien rich foods.
