So when my house was being treated for termites, 3 day fumigation, a few years ago I looked into how people delta with such issues and a reef aquarium. In the end I moved it to my friends down the street and when it was over built a new, larger tank, and upgraded. But along the way I heard a number of success stories of sealing off the tank with plastic and using a good air pump for fresh air. Basicaly buy the thickest plastic you can from home depot, usually like 6mil and around $10-20. Drape it over the tank and tape it too the floor sealing it off, similar to what you would do to tent a whole house. Then run a hose to an air pump somewhere in your yard under the seal to supply fresh air. I've heard of it being done like this on tanks in the 300g range where tank moving isn't an option but they need to fumigate to protect the house and chemicals much worse than a bug bomb. So buying some plastic an air pump and hose seams to be safe and simple, just use a lot of tape, seal the openings really well and keep positive pressure of fresh air.