benzenering said:
This is the antibiotic I myself would use for internal protozoan, as a first step anyway. Twice I have stopped a "mysterious" problem killing off 1-2 fish every day, which obviously was from some protozoan. However, I gather this antibiotic is much more effective taken internally, which means medicating their food. This should be done for no less than 10 days to 2 weeks, with no food other than the medicated being fed, so the fish are more likely to be eating it. I have read fairly professional articles saying much the same, that metro is best when ingested. Seachem make a product called MetroPlex which is straight metronidazole, this may be the one you have; but there are some other brands.
If the internal protozoan is the issue, so far as I know it spreads from fish to fish, but not on objects within the tank. I have added new fish to my tank after this treatment (waiting 4+ weeks after the last fish death to be sure) and it never came back. This was on the advice of a very knowledgeable aquarist. I had some internal protozoan twice, both times (a good two years apart) introduced with new acquisitions. Hence one learns the value of quarantining. I've no idea how effective it is when added to the tank water, with respect to internal protozoan and parasites.
As to the time period, like all antibiotics, they must be continued for the prescribed period, regardless (unless obviously if it is one that is harming the fish or something), so I would do the period recommended on the label if you use it.
Byron.
