It just stopped raining so I decided to take a walk through my collection. As I was walking, I noticed that there were weeds growing in the pots. Would weed killer be a good weapon without hurting the cactus?

You don't have to make it yourself. You can go to an Asian supermarket and buy some there. Their aloe juice actually isn't bitter, it is actually sweat with the aloe pulp blended into the juice.

I can't really see it. Can you take a closer picture of it please? From here, it looks fine.

Hi. I just joined the forum and I have been collecting cacti and succulents since I was in fifth grade. I have been taking care of them ever since. I will be posting some pictures of my collection when they come out of dormancy in the Spring.
Very helpful website Daiv. Thanks.