My dog has had mushy or muddy diarrhea on and off for a month, sometimes normal; he is 6 years old, energetic with good appetite, and the stool is slightly green

Soft, muddy stools indicate gastrointestinal upset, possibly from overeating, irregular feeding, bacterial infection, or internal parasites.

Do not ignore it. Ensure the kibble is well sealed and unspoiled, feed on a regular schedule with two meals a day, and avoid non-kibble foods that cause indigestion.

During diarrhea, reduce portions and add probiotics, then observe. If there is no improvement, take the dog to the clinic for a fecal or blood test to rule out parasites, gut flora imbalance, or infection, and treat accordingly.