Wow that's a very heavy duty tank. Going to last you some good years that one will. I wish I could come by a deal like that on thick plywood.
Good call not mixing polyester resin for your fiberglass with an epoxy top coat - they will co-exist if done properly, but not very well. Not nearly as well as polyester to polyester or epoxy to epoxy. For your flood coat/top coat, are you planning on using the boat-kote epoxy as well? I don't think you'll have a problem but you might want to look into it's fish-safeness. I know some epoxies create by products as they cure called amines. Most of the time you can wash the by products off and be left with an inert, safe surface, but not with all epoxy resins, particularly if you get the mix ratio off a little bit. Just a thought!
Looks like a ton of work! I can speak from experience, sanding fiberglass reinforced epoxy is not fast, fun, or easy - especially inside a tank, and especially with a tank this large! one missed fiberglass "needle" too and you can give yourself nasty cuts on the stuff. Looking forward to updates - looks like it's going to be a great tank.
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