Disclaimer: Although I have a fair amount of experience with electrical work I am not an electrician. You may need a qualified electrician to do the electrical around your aquarium. Check your local by-laws.
To prevent any shock hazard you should install a GFCI outlet. This is the same type of outlet you’ll find in your bathroom. A typical aquarium will have a light, filter and heater. Some larger aquariums like our Jumbo Wall Aquarium has 2 lights and 2 filters and a heater. This means that you will have 2 – 5 devices that need to be plugged in.
Your outlet should be concealed inside your wall opening in one of the top corners. Make sure not to install it in the top center, it might interfere with the lights placement. Once you have one GFCI installed you can wire additional outlets off of it that will have the same properties (refer to the GFCI’s instructions). A second outlet in the opposite corner will be useful for larger tanks with extra devices.