HCA: Hermit Crab Association

Mine arrived today, looks like a nice quality product. Is there any adhesive on it? I couldn't find any so I attached it to the back of my 10 gal with packing tape. Am I supposed to see stripes along the back wall or am I doing it wrong? Please post pics of your tank with Ultratherms. Also, it feels...

I have 2 small crabs in a 10 gallon aquarium with about 5 inches of sand/eco earth and a crappy uth zoomed heater thingy that isn't doing squat. I live in Texas, but keep the house pretty cool. I think this is why we don't see them very often. I have both a salt and a fresh water bowl. What size ult...