Ulcerative colitis (UC) is a disease that causes long-term inflammation in the digestive tract, and many people with this condition require surgery to remove the colon and create a new J-pouch for stool. Some patients develop a problem called pouchitis, where this pouch becomes inflamed. Current treatments are limited, and there are no known ways to prevent pouchitis from starting. This study is being done to find out if a natural mineral supplement called Aquamin® can help reduce inflammation and protect the gut lining in people with a J-pouch, and may reduce the risk of pouchitis. By understanding whether Aquamin® is safe and helpful, the study team hopes to find a new and better way to prevent inflammation and improve the long-term health of people with UC.

Inclusion Criteria:

• Must be able to give written informed consent (or assent as appropriate)
• Must have the following: UC with ileal pouch-anal anastomosis (IPAA) using a J-pouch without an ileostomy within the last eight months
• For pre-menopausal women 11 years of age and older with intact reproductive organs, a negative pregnancy test is required within two weeks prior to the baseline visit. Participants in this age group must agree to use an acceptable form of contraception throughout the study per protocol.

Exclusion Criteria:

• Female subjects must not be pregnant or lactating; and female of childbearing potential unwilling to use acceptable birth control throughout the study.

• Must not be participating in any other interventional trial using an investigational drug.

• Subjects likely to be uncooperative or unable to comply with study procedures

• History or diagnosis of Crohn's disease

• History or diagnosis of hereditary gastrointestinal (GI) syndromes, Severe gastrointestinal bleeding/complications, (gastrointestinal bleeding from gastric or duodenal ulcers, or gastrin-secreting tumors).

• History or diagnosis of any gastrointestinal malignancy

• Kidney disease, including kidney "stones" or hypercalcemia. acute renal failure (past 12 weeks). (Note: A doubtful stone passed in the urine more than three years ago is not considered evidence of current renal stone disease.)

• Congenital coagulopathies or hereditary hemorrhagic disorders; treatment with therapeutic doses of warfarin or heparin

• Participants will be excluded if they have used any of the following within the past 30 days or are unwilling to withdraw for 30 days prior to entering into the study:

  • Calcium, Magnesium, including multivitamins that have low amounts of Calcium/Magnesium and fiber supplements. (Multivitamins without any minerals are allowed).
  • Non-steroidal anti-inflammatory medications (NSAIDs), such as Naproxen or Ibuprofen (except for occasional pain control or low dose aspirin for cardiovascular disease prevention) per protocol.
  • Oral or rectal Corticosteroids (a type of steroid drug such as prednisone or cortisol that helps the body to regulate stress response, immune response and inflammation) and antibiotics (except these can be used briefly during a flare-up once the study treatment has begun after the subject enrolled, if prescribed by the personal physician). Inhaled and skin corticosteroids preparations are ok and not an exclusion criteria.