After the glass has been cleaned, take out any decorations, rocks, or artificial plants that are causing significant algae growth. You should not use soap or detergents to clean them. It is very difficult to remove soap completely and can cause damage to fish.
Make a 10% bleach solution and soak the items in it for 15 minutes. To remove any residual bleach, scrub the items with a sponge and rinse in warm water. You should not put them back into the aquarium until you are satisfied with the chlorine smell. To remove chlorine, you can rinse them with water that has been diluted with dechlorinator (sodium trisulfate).
To remove algae from live plants, bleaching can be done. Stem plants are not sensitive to bleaching. Bleach live plants by using a bleach solution of 5 percent. After soaking the plants for 2 to 3 minutes, rinse them well.
While you are removing gravel, decorations and rocks, be sure to remove any plants. This will ensure that no gravel particles settle on the rocks.
Make sure you get a brand new bucket that is only for aquarium use. You could accidentally introduce chemicals to your aquarium by using a bucket with soap or detergent.