Does the bottle list the ingredients?
I imagine that the content and the results are the same. Only thing that springs to mind is the dosage level - for a pond you would have to add more, not only for volume, but also to allow for evap, dilution due to rain, etc.
I just searched for it and it contains malachite green which does cure ich, so it should work - just would be careful with the dosage - it can treat up to 960 gallons!