With fish you want a hardy fish.
I have used Zebra Danios to cycle with and never lost a single one.
I used to keep a school of 10 in my 46 gallon, you don't need that many but they do like to school so at least 4 or 5.
Amonia? I used 1/2 teaspoon in my 75 gallon but concentrations vary so start out low. It is easier to add more rather than have to change water because you have too much.
I used 3ppm amonia level to fishless cycle with great results.
You will need a good pure amonia with no additives. Shake the bottle, it should act like shaking water, if it forms any bubbles it is not good to use.
The only place most members here, myself included, have been able to find adequate amonia is Ace hardware with the Ace brand industrial amonia 10% amonium hydroxide.
In either method a good test kit is a must as the amonia, nitrite and nitrate need to be closely monitered. I recommend the API freshwater master test kit.
PS: if cycling with fish never let amonia or nitrite get above 1ppm at the most, partial water changes are required for a fishy cycle.
