Turkey basters get my vote as best overall gadget for a tank. I also like the extra long handled tooth brushes with a brush at each end with an angle to them, and normally sold with a tube of tooth paste for dogs. They are about 12" OAL, and was just on clearance at Petsmart for a buck.....Great for odds and ends in the tank especially the smaller brush end shaped like a triangle...Does corners great.
POwerhead for me to mix salt also, hang over side of container, plug it in and forget about it..cheap too.