A housing for aquatic flora and fauna that has at least one transparent side or viewing pane that can be used to view the aquatic life from the general public. When visiting an aquarium, it is not uncommon to expect to see fish, aquatic mammals, reptiles, amphibians and lots of plants.
The viewing pane is normally made out of thick glass or acrylic, glass can distort the image somewhat and make the fish look bigger than they actually are, sometimes this effect is desired and sometimes not. The term aquarium is however used on a wide range of size enclosures, from the 2-gallon bowl you keep your goldfish in to the many thousand-gallon tanks used to house sharks. Water pH, salinity, oxygen etc. is usually maintained electronically with special equipment in such big tanks but regular checks on water parameters are carried out just to make sure.
Robert Warington first showed the feasibility of aquariums in 1850, he proved that plants give off enough oxygen to sustain fish as long as their population didn’t get too large.