Just a couple of thoughts here....if it was me, I would ditch the skilter. I have known people who had them, I have read posts from people who have them and I have never heard of anyone getting one to actually work!
Check out some of the internet sites, there are tons of skimmers out there that don't cost an arm and a leg and that really work too!
The texas holey rock or whatever name you want to give it, is a safe rock that can be rinsed well then simply added directly to your tank. Won't hurt a thing and here's a bonus too. If you buy a piece that has holes going deep into the rock but small enough that fish can't get into them, you will be providing a perfect spot for amphipods to breed and live in. I have a large texas rock in my tank and whenever I look in the tank at night with a flashlight, there is always a party going on in that rock! Tons of huge amphipods running all over the place! Serving beer and having drunken fights.....well, okay, not the beer and fights but you get the idea
Instead of the garf grunge, do you know somebody that has a saltwater tank that could give you a couple of scoops of their sand? Or you could order an starter kit from one of the on-line pet stores......