There is no doubt that aquariums need to be grounded. Although this may not have been "that" obvious a few years ago, the concensus among hobbyists nowadays is that grounding greatly improves tank conditions and may prevent lateral line disease.
Grounding your tank is not complicated at all. Do not think you will need some very intricate piece of equipment that is going to cost you hundreds of dollars, and is going to be really hard to maintain and install. This is not the case a t all. Grounding your aquarium is easy.
It is performed to remove "stray" voltage from the aquarium, stray voltage that comes, or may come, from implements such as powerheads, pumps, lights, inductive currents, pumps and so on. There are many sources that could put such low voltage currents in your aquarium and these currents need to be eliminated.
You will need two pieces of metal wire. One can be just regular metal but the piece that is immersed definitely needs to be salt water resistant. This sort of metal "may" seem hard to get and may appear to be expensive. It is not at all. It is extremely simple to get. Go to any bicycle shop and buy a "titanium wheel spoke". They cost around 2 or 3 dollars a piece. Nothing really expensive!
The Titanium spoke is the "only" part that is immersed in the water. To the end of the Titanium spoke you simply attach a length of regular metal wire, e.g. stainless steel or any kind of metal. You can even use copper, as long as you can make sure tha t it will never get into the salt water. That is the reason I prefer to use stainless steel. Better safe than sorrow.
Run the other end to a good grounding element. This is perhaps the only difficult part of the whole process. You must find a real good ground.
A good ground is the screw in the middle of a grounded electrical outlet. Make sure, though, that if you use this method that you remove the paint from the screw, or you will not have a good ground. Make sure too that the outlet is indeed "grounded". In modern houses they would tend to be, but in older ones you may need to test them. Hardware stores sell an inexpensive tester that allows you to do so. The last time I got one I paid around $ 5.00 for it.
Any water line, usually copper, is a good ground too. Clean the portion to which you are going to attach the wire well, so the oxidation is gone. Rub the pipe with sandpaper or a metal brush.
Other grounds can be found. Look around at what is close to the aquarium. My experience though, is that grounded electrical outlets are usually the easiest to use and are always nearby enough the aquarium to be able to be used.