Metronidazole works quite well for many parasitic infections. It works even better at higher temps, around 90 degrees F. However, telling the difference between HLLE and HITH is not the easiest thing in the world. What size tank is your pike in? I would just keep up with the significant water changes, vitamins, and diverse foods. It may help to drop the GH of the tank as well, as many blackwater cichlids suffer from HLLE due to elevated bacterial counts and stressful water conditions. Metro will do nothing for HLLE. It may help some with HITH. Either way, it will definitely help clear out internal parasites. Nice pike - good luck with it!
J