Frankfurt / Main (AP) - Europe's currency guardians are using all means against the economic slowdown: Banks have to pay even higher penalty interest in the future, if they park money at the European Central Bank. In addition, the central bank is investing billions in bonds. That was decided by the ECB Council in Frankfurt. Thus, the central bank again tightened its ultra-loose monetary policy. The key interest rate, which has been at a record low of zero percent since March 2016, remains unchanged at this level.