Fishgirl, I imagin when they start sanding on the floor the vibrations could be very stressful to your fishies.Not to mention the dust,take my word it gets everywhere. If your tank isn't sealed off it WILL get in there too.Try to put plastic over the top, seal it to the tank with tape. That should keep out the dust.To keep out fumes and POISON, after the tank is sealed take an air pump and set it in FRESH AIR (say outside a window) run an air hose into the tank.Yhe plastic will swell if you have it sealed properly. Then poke small hole or two in the plastic. What you now have is an over pressurised, containment system. No dust or poison can enter as long as possitive pressure is maintained. Learned that trick in the army.(nerve gas protection) Hope this makes sence? STEVE