I'm a FW
guy and know virtually nothing about SW
, but I'll chime in on what I can. "Pure" and "Clear" ammonia are not necessarily the same thing. You want to make sure the bottle you have is simply ammonia and water. You don't want any dyes, detergents, surfactants, scents, etc... Ace Hardware is a great place to pick it up, and it's also readily available online.
Here's a fishless cycling ammonia calculator. Type in your tank volume, the ppm
you're shooting for and the strength of your ammonia. It will give you a guideline of how much to add.