Not if you stand idle.
Empty 1/3 of you tank every week and replace with fresh water. That should keep things leveled.
A fish actually excretes ammonia dissolved in water. At the temperature and pressure that fish are normally found ammonia is a gas.
Fish smells like ammonia when it starts to spoil.
Ammonia is harmful to fish. Its is a by product of the nitrogen cycle, which is what keeps the water stable in your tank(i wont delve into that) but yes ammonia can burn fish, especially those who lack scale's.
Is it ammonia
Cod fish or any type of fish will have ammonia like smell when it is no longer fresh. This smell will begin to appear as you are cooking it. It may also have a taste that is similar to ammonia, too.
No
Yes ammonia can do that. It is toxic for rats.
It would die. The ammonia would kill the fish if amounts were elevated.
The fish is undergoing normal decomposition, which releases ammonia. The fish may be too "expired" at this point to eat. If in doubt, throw it out!
Ammonia can be built up in them separately or the two together. Some species of fish produce more waste and therefore more ammonia than others, for example the goldfish. Turtles are also very wast producing and turtle tanks are often high in ammonia. All fish produce ammonia. So yes.
Yes
Ammonia can be found in people also over 10,000,000 people have it in them and die from it