Thanks for you posts guys! Im not a fan of H2O2, it would kill both, the good and bad bacteria. Since the undesired "whatever" seems to outcompete the good ones, H2O2 would make the problem worse. Or i would have to run with H2O2 for the rest of the grow.
Its a shame that you can't get Hydroguard/Aquashield in Europe, what sterile agent would you propose?