Seachem MetroPlex is probably the best of the Metro based medications out there. It seems to work very well whereas other brands Ive used actually seem like they have difficulty dissolving. This stuff is such a fine powder it dissolves quickly and completely.
My dosing lets me use the entire contents of a tube in my treatment but I understand that technically this product is by weight and not volume in the container. kind of like that bag of chips you buy at the store. That being said if you need to dose this out in smaller doses the best way would be by weight and not the little spoon they give you.
Have to also give a lot of praise to Pet Mountain for carrying this product in a 6 pack for a reasonable price. I always keep it on hand in my fish first aid box.