I am asked all of the time if Pond Shield will hold up in a salt water environment. The answer is yes it will. In regards to water proofing a salt water aquarium or tank, I am not going to talk about the construction of the tank here.
If you would like to know more about the actual constructions, then following this link: How to Build a Wooden Pond or Tank to the article I wrote about that. If you have not seen this article and are considering building your own tank, I highly recommend that you read it before you start. You will probably find some things in it that you may have over looked.
With that said, there are a few things you need to remember when coating any aquarium or tank, regardless of it being for salt water use or not.
If you are trying to coat glass, you are going to have to etch or rough up the glass first. A surface like glass has no surface tension and without roughing that surface up, the coating will soon fall off.
When coating wood, it is best to thin a small amount of Pond Shield and coat the wood surface before coating it with a normally mixed batch. This thinned down version of Pond Shield will act as a primer and drive little epoxy fingers deep into the wood grain where the bond will be that much better.
If you are going to have a glass viewing window in your salt water aquarium or tank, you will still need to coat the wood that the glass will rest against. It is best to rough the coating up some after it has cured where the glass will rest so that when you use a fish safe silicone to seal it, the silicone will adhere better to the coating. If you can etch the part of the glass where the silicone will come into contact, that bond will be much better as well.
Other than those things to remember, the coating process for a salt water aquarium or tank is pretty much the same as any other surface.