Yes Pond Shield is a stand alone product. After acid washing the concrete with muriatic acid/water, you wait until it dries and apply Pond Shield directly to the concrete. This saves you the time and hassle of primers or pre-sealers. As far as the sealer one would use to seal an acrylic window in, JohnPTC did it perfectly. Pond Shield as the base material and then the actual flexible sealer between the coating and the acrylic. I'm sure JohnPTC did, and I would recommend always scuffing the cured Pond Shield before the flexible sealer for the window is applied. The more tooth you have the better those sealers hold.
JohnPTC - I saw your link to your tank. Very impressive. I didn't want to post in your thread so as to keep it as pure as possible. Your thread is about your constructiuon and I find that once I post into a thread, people start asking questions thereby diluting the thread. So this thread seemed the most logical place. FYI, I have an installer in Hawaii that did a pond with a couple of acrylic windows like your tank has. He used a very similar method for installation and his client couldn't be happier.
Butch
Pond Armor
www.pondarmor.com
800-716-1545