I haven't used Aqua Defense, but I have used Permadri which is the US version of the original Canadian Zavlar from liquidrubber.ca. Not all liquid rubber products are indeed fish safe. In example, Blue Max won't guarantee to be fish safe. After using a liquid rubber product, I would steer you toward an epoxy product. Max ACR available on Ebay is the choice of some of the most respected builders on MFK and what I'm going to be using to finish my build.