Just saw this new style caulking gun. It would be great for any aquarium silicone jobs due to it's compact size and form factor! No long metal rod plunger makes it ideal for projects like resealing aquariums or siliconing in baffles in a diy sump!
Looking at that picture I can't even determine how that would squeeze anything. Magic with magnets or something. Then I saw that it slices the tube. Not as magic as I thought, and useless until it's useful. Still good innovation.
If you are resealing an aquarium or building on I would highly recommend the Ryobi ONE+ 18V Power Caulk and Adhesive Gun. Its only $50 if you already have their tools and batteries. Once you get past a few tubes by hand and you have a limited working/skin time to complete the reseal the battery operated caulking gun pays for itself.