You can use muriatic acid, or ph down to keep your ph down. You can get skimmer socks at any pool supply store - here is alink to what they look like, it is the third one down on the left:
http://www.poolgear.com/index.asp?Pa...TS&Category=64

You can find them cheaper if you shop around, but this has free shipping. You can also cut off a leg of pantyhose and put it on the skimmer. It just catches small particles that the filter sometimes doesn't get