My first question was going to be: are you sure he is a male? Large poops often precede an egg. If there is an egg, do not remove it . S/he will just lay more to replace lost ones.
He should go to an avian-experienced veterinarian ASAP for complete examination, diagnosis and appropriate treatment. Check the link http://www.aav.org/association/index.php?content=activeMembersList
for members of AAV in your area or call your regular vet and see who they recommend. His/her droppings should be examined for parasites and bacteria just to make sure everything is ok. Bacterial or protozoal enteritis can cause large droppings.
Pet/feed store medications are harmful, ineffective, immuno-suppressive, and make them much worse and may interfere with the veterinarian's diagnosis and treatment. Do not use them.
If he is a she, them you need to do everything you can to discourage egg production. It is very hard on them. Photoperiod, diet and sexual stimulation are important factors.
Birds should be on a high-quality, preferably prescription, pelleted diet. In addition, they should be offered dark leafy greens, cooked sweet potatoes, yams, squash, pumpkin; entire (tops and bottoms) fresh carrots and so forth. No seeds (and that means a mix, or millet, or sprays, etc etc.) and only healthy, low-fat high fiber people food. A dietary change should be closely monitored and supervised by your avian vet. High fat diet (seeds) causes estrorogen spike and ovulation.
Birds should get 12-14 hours dark, quiet, uninterrupted sleep at night. Any less and they can suffer from sleep deprivation and associated illnesses. They should be covered or their cage placed in a dark room that is not used after they go to bed. Longer dark hours is a natural way to decrease estrogen.
The cage material should be cleaned everyday, and twice a day if the bird is really messy. Paper towels, newspaper, bath towels are ok. Never use corn cob, sawdust, wood chips, or walnut shell. And no nest-like structures.
Never give grit, gravel sandpaper or cement perches. A bird will eat those to excess when it is not feeling well or if there is a nutritional deficiency. They do not need it at all (an old myth from the poultry days, even poultry do not need it). It can cause an impaction and lead to serious or fatal consequences.Calcium deficient birds (females laying eggs) will eat it to huge excess.