Re: 6ft./150 gal first time Palu build...
I've built three ponds using EPDM liner and never had a problem. I did purchase them from a pond retailer and they were made for fish/ponds. I felt comfortable using them.
As far as the silicone, I believe a large number of hobbyists have purchased the wrong type of silicone without realizing there are two different types. I believe it's GE Silicone I and II correct? I don't use that brand so I'm not to familiar with it. I always try and find 100% pure silicone and then make sure it doesn't have any mold/fungus inhibitors.
Great info jpstod, thanks.