Is the wall the door is in a bearing wall?
that means it is designed to hold things up. You can tell this 2 ways, it should have something under it in the basement or crawl space to hold it up, and it should run perpendicular to the floor joists. If its a bearing wall then the doorway should be designed to hold weight above it and should not be any problem.
Does this mean you should just through the tank up there on my word alone? No
A good idea would be to get some 55 gallon plastic drums from somewhere and sit them where your tank is going and fill them up with water one at a time. Check along the wall behind where the tank is going, the door frame, and all the drywall along that wall for cracks as the weight is added. Also check to be sure the floor that they are sitting on does not bow down. Make sure to use enough barrels to account for the 150 gallons, plus the stand, equipment, rock, sand, sump, and a couple of people standing in front of the tank gawking!
good luck
Oh, I just noticed you are in Alaska, it might be hard to get those drums there, they are ordinarily used for things like vegetables and such here.
