I don't usually question Ben, but if you are using a cartridge filter (which is common with Intex pools), DE may not be a good idea...DE can clog up some cartridges (if not most). Plus, if you don't have a skimmer (and most Intex don't) it's VERY difficult to get it into the filter. You can safely skip the DE until we figure it out, so don't worry about that.

PolyQuat is usually only available at pool stores or pool sections of places like Wal-Mart. It's called algaecide, black algaecide, yellow algae algaecide, or other stuff, but the important part is that there is only ONE active ingredient:
Poly...<something long and unpronounceable>... 60%
Anything else is the wrong stuff. "Small amounts" means 1 to 2 ounces--and with a small pool stick to 1 ounce.