Regarding the aquarium landscaping, I bought a new 50x30 aquarium and some aquatic mud. Want to landscape the fish tank! But I heard that the fish tank has been disinfected and opened.

Disinfection is only to prevent parasites from surviving in the box. Stones, water plants and the like bought from outside should be disinfected before being put into the tank. To tell the truth, this kind of cylinder can be washed with water and wiped with cloth. There is no need to sterilize the cylinder. Open the jar ... since you are a beginner, you just need to buy some fish that are easy to raise (you can ask what fish are easy to raise, or ultra-simple zebrafish) and then put some nitrifying bacteria, so that you can buy some other fish in a few days or a week. Now we should be careful not to let the fish freeze to death in winter, and then don't raise too many fish at once. My personal standard is not to make the tank look too crowded and unsightly, so be it (by hand).