Ice-binding proteins from the sea-ice microalgae Fragilariopsis cylindrus (fcIBPs) belong to a protein family widely spread among several organisms, from sea-ice microorganisms to cold-tolerant fungi. Their mechanism of action, the interaction with ice crystals and their influence on ice growth, differs from the one observed for fish or hyperactive AFPs. In order to understand the attachment process of fcIBPs we observed free growth of one ice single crystal from the melt. We present a new growth pattern of ice in the presence of IBPs. We used bright field microscopy and Mach-Zehnder interferometry to determine crystal morphology and growth rates parallel and normal to the basal plane. We corroborated our observations by fluorescence microscopy using the fcIBP fused to a fluorescent protein. Our results all indicated that fcIBPs bind preferentially to the basal plane, and to a less degree to some prismatic plane of the ice crystal. Whereas the observed strong suppression of growth normal to the basal plane was expected as directly reflected by morphology observations, ice growth enhancement by fcIBPs in direction of the basal plane, never observed before in other IBP kinds, was surprising. Set in a natural frame, the proteins, expelled from the microorganisms in the brine space primarily located between the basal planes of elongated crystals of columnar sea ice, may be helpful in maintaining a liquid environment by strongly controlling ice growth on the basal plane.