Blockchain is a distributed ledger technology that enables cryptocurrencies, such as Bitcoin and Ethereum. However, it suffers from the scalability problem, which means that not all generated blocks can be added to the chain in a timely manner. For the Internet of Things (IoT), which involves a large number of interconnected devices, blockchain is infeasible due to the scalability issue. Instead, a different distributed ledger technology, IOTA Tangle, is expected to be widely adopted in IoT applications. Nevertheless, it has been found that the tip selection and weight update operation of IOTA Tangle could negatively affect its efficiency. To tackle this problem, Fishing Net Topology (FNT) was proposed to completely eliminate the tip selection and weight update operation. However, in our research, we noticed that the width of the fishing net used in FNT remains unchanged, which has a serious impact on the performance of FNT. In this paper, we focus on Wireless Sensor Networks (WSNs), which are often used to implement IoT applications. Specifically, we present a secure data storage scheme based on FNT for WSN, Adaptive FNT (AFNT). Our experimental results indicate that AFNT outperforms FNT in terms of layer number, average fishing net width, percentage of over-approved nodes, and percentage of over-approving nodes.