drywall and reef aquarium

[Quagmire]

My .02 as a part time drywaller is to agree with scotchy.The dust is from the mud.Even if by chance the dust did come frome the drywall,its not 100%
gypsum.Lots of chemicals are added during the process of crushing,baking,forming etc.Even if the gypsum was OK in a tank,the additives would cause problems.Maybe a good idea to scoop out what you can,and put a towel or blanket over the tank when the taper is sanding.

[Ruth]

Another thing that works well for covering a tank is to use plastic wrap and just keep wrapping it around and around. It gives you a much better seal that a tarp.