Changing aquarium water,etc.

[Aquawater]

I have a freshwater tank and I need to do a full water change. And I’m changing the gravel as well.Too much moss, alga and when you stir up the gravel the tank becomes way over clouded. Most of the gravel is removed and the bottom of the tank is covered with debris.. Any recommendations on how to achieve this task?
Just drain the tank and clean with some sort of cleanser ? If so what do you recommend? Pic below is on its side?

 

[earhtmother]

Best cleaners for tanks are vinegar, aquarium salt and elbow grease, NEVER soap. It sounded like you had already removed the gravel, so if all that is left is *crap* then simply using a clean rag is the easiest way to remove it. If you have a gravel cleaner you should use it at least every other week during water changes to help preven the build up happening again. If you don't own one then you need to get one.