I dont know about amazon but buying pure ammonia without additives in the uk is illegal, im sure you could import some from some where if you wanted to though. There's an aquaria based alternative by waterlife called biomature which is an ammonia based solution which ive used for fishless cycling many times with great results.
Depending in your tank size, 100ml should be able to cycle upto 20gallons but anymore i would get 2 bottles or a bigger 500ml bottle.
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Fish die belly upward and rise to the surface. It's their way of falling.