Can this product be used to skim coat a concrete fountain basin to make waterproof?

No, do not use QUIKRETE® Hydraulic Water-Stop Cement to skim coat a concrete fountain basin. If the concrete fountain basin is not already sealed, QUIKRETE® Heavy Duty Masonry Coating blended with QUIKRETE® Concrete Acrylic Fortifier replacing a portion of the water content as per instructions may be used to “paint” the inside of it with two coats if it only has very thin hairline cracks. If there are larger cracks present, they should first be repaired with an appropriate product before applying the coating, such as QUIKRETE® FastSet Repair Mortar No. 1241 or QUIKRETE® Vinyl Concrete Patcher No. 1133. Neither of these will be a color match to the existing bird bath. Products containing cement, such as QUIKRETE® Heavy Duty Masonry Coating, QUIKRETE® FastSet Repair Mortar, and QUIKRETE® Vinyl Concrete Patcher change the pH level of any water with which they have contact during the curing of the material. They should be allowed to cure for 28 days, then be rinsed thoroughly, before the bird bath is returned to service for the birds. Refill it with water, then continue to monitor the pH to ensure it has stabilized. Please call the QUIKRETE® Technical Center at 1-800-282-2858 to discuss further.