Tönnies was best known for playing for MSV Duisburg, playing in 179 league games and scoring over a hundred goals. He also played for Schalke 04, SpVgg Bayreuth, 1. FC Bocholt, Rot-Weiss Essen and Wuppertaler SV. He held a Bundesliga record, scoring the fastest hat-trick (three goals). He held the record from 1991 until 2015, when Robert Lewandowski beat the record.