I recall seeing something about good and trace elements. Is it a particular kind of food that works best or vary on ratios? I feed mostly frozen. Would pellets or flake have more since they tend to pack in vitamins?
I don't know what foods might be best or worst with respect to trace elements. A study of what is in them, such as some folks have done in the past) does not really say how much of what is released to the water when the food is metabolized. Companies do not need to add them to the food for them to provide many elements, since most are already an integral part of the things used as the food components (such as shrimp or nori).
My main reason to post here was to remind folks that water changes and dosing are not the only ways trace elements get in, so that someone doing neither of these is still adding trace elements. :)