Let me rephrase what I wrote. I plan to have GFCI, but haven't decided which way to go. I don't think it's necessary as far it being a safety issue because there won't be any electrical contact with the water in the tank.
In regard to anything meeting code, being legal, or whatever you have in your head. How many people build an aquarium or even have one 1/4 this size in their home? Anything legal, I have a very good attorney who is also my best fish nut friend who also has 2 2K plus tanks in his own home. Sure, they could probably say some code violation and make me change the electrical, but that's about it. I'd like you to show me what law there is against having an indoor swimming pool, pond, or gigantic aquarium.
Ask yourself this; is every outlet in all your bathrooms GFCI? Is every fixture sealed and/or have a UL whatever listing? I doubt most can answer yes on both of them.
The top will be covered with thin plexi on pvc frames, but will still have some venting for gas exchange.