I have an in ground pond and I used Firestone's pondguard pondliner. If your dog's nails can puncture it you have something other than a dog! It's a bit on the spendy side but well worth it with the 20 year gaurantee against UV degredation. and it's nice being able to build your pond in the shape you want with plant shelves etc. You may be able to find it cheaper at an LFS or pond supply store, here is a link to buy it on the web http://www.pondsupply.com/firestonepondguard.html I live in PHX AZ and it has been over 110 for the past 2 months my fish are great and healthy and my dogs go for a dip in the pond quite often with no ill effects. Hope this helps.