Hello; Allow me start with my version of an answer to the cycling question. When I began, around 1959, the term cycling was not used by anyone that I was aware of. Back then I came to think of it as “aging the water”. I learned fairly soon that a newly set up tank went thru stages for several weeks until it became mature. Once mature a tank can stay set up for several years with reasonably simple maintenance.
If starting with new tank, gravel, filters heater and other stuff, I do the following. I will fill a tank with water to check that it does not leak, empty it and then clean it with a paste made from non-iodinized salt. (This paste can be used with a soft sponge or cloth to clean the crud in an old tank without scratching the glass. (Make sure the sponge has not been used for anything else. I usually buy a new sponge and use it only for my tanks. ) I rub the paste on the inside and outside of the glass and then rinse it away. (This cleans the glass and flushes away contaminants that may have gotten in the tank.) I rinse the new gravel several times until it is fairly clean. I then put the empty tank on a stand and level the tank. Put the gravel in and add water. Set up and start the filter running. I let the tank sit for two or three days with the filter running and use this time to get the heater set to the desired temperature. (It is also a good time to check again for leaks, as there is no mad scramble to find a place to put fish if it does leak.) I will allow the tank to stay this way for a week before thinking about adding fish.
At least two things happen during the week the tank sits. One is the chlorine and chloramine from the tap water need to be taken care of. If you happen to be where the water company only uses chlorine all that is needed is to let the tank sit empty a few days. I am in that kind of place. If the tap water has both treatment chemicals the chloramine does not simply dissipate and some sort of water conditioner is needed.
Another is the tank will sometimes develop cloudy water to some extent as bacteria bloom and the stuff remaining in the gravel gets into the water. This is usually only for a few days.
What I called a “mature tank” is now usually called a "cycled tank". The fish, snails, other animals and decay of organics in an aquarium make waste products as part of metabolism. Some of the waste is mostly only unsightly but the ammonia waste is toxic. Over a day or few the ammonia can build to harmful levels in a closed system like a tank. The fish get harmed as the levels of ammonia built up. There are three ways to deal with the ammonia that I know of.
First way to deal with ammonia is large and often water changes. This removes some of the ammonia and dilutes the remainder with fresh water. If you put too many fish into a new tank setup the ammonia will need to be diluted often. The fish are constantly releasing ammonia into the water.
Another way to deal with the ammonia is to grow a lot of the right sort of bacteria. Turns out there are natural bacteria we can grow in our tanks that change toxic ammonia into a much less toxic chemical. This is what “cycling a tank” is about. Getting these bacteria to make a home in our tanks.
One good thing about these bacteria is they will eventually find a way into our tanks on their own. Trouble is it can take many weeks. So until the bacteria become established the water change will be your friend.
There is a way to speed up the “tank cycle” process. That is to get some solid material from an already “cycled “ or “established” aquarium. Solid surfaces from a cycled tank have colonies of the bacteria living on them so adding this to a new tank gets the bacteria into the tank.
The last way is the use of commercial products. I have never used them myself so cannot give reliable information. Maybe others can.
Good luck
