I USE ROMAN LETTUCE. I JUST PUT HALF A LEAF IN THERE A DAY. I TAK EIT OUT EVERY NIGHT. SOME TIMES I WONT PUT IT IN THERE. I WOULD SAY 3 OR 4 NIGHTS A WEEK TOTAL, ON AVERAGE. SOMETIMES ALL WEEK. USE A LITTLE COMMON SENSE. IF IT LOOKS BAD TO WHERE YOU WONT EAT IT THEN DONT GIVE IT TO THE FISH. ALSOLOOK TO OTHER ALTERNATIVES TO FEEDING. NOT JUST LETTUCE. AND DONT GET HOOK ON IT. WASH IT REALLY WELL. TRY MAKING YOUR OWN FOOD WITH ZOE FOR GOOD NUTRITION. GOOD LUCK!