I've been hearing arguments both ways about treating new fish prophylactically. I currently quarantine all new fish but was wondering if maybe I should treat them for parasites prophylactically. The reason I want to be a little more proactive is that I've lost quite a few fish while in quarantine and think that perhaps some could have been saved with treatment. I also think that while quarantining new fish helps avoid many problems, it is not 100% failsafe as a fish can be carrying a parasite load ( or bacterial infection ) which is just below threshold for causing illness or death in that fish but once introduced into your DT can sicken or kill other fish.