Okay, so my cockerel seems to have some kind of respiratory problem (rattling when he breathes). So I got some Terramycin (oxytetracycline HCI) soluble powder. According to the instructions, I need to give a dosage of 400 milligrams in every gallon on water. But I don't have anything that measure milligrams, or even grams. I can measure teaspons, tablespoons, ounces, cups, milliliters... but no grams. Does anyone have any idea how to convert this? I googled it but couldn't come up with a way to convert milligrams to milliters or any other measurements I had.