We do wish that as children there were the various "Big Food Super-stores" of today, with their one gallon glass jars so readily available. What a treasure! Imagine the Bettas, Paradisefish, tadpoles... you could've kept! Practically speaking, most anything that can hold water and not mal-affect its chemistry can be made to work as an aquarium... plastic sweater-boxes, tubs, totes, "pickle buckets", and much more, though the traditional aquarium is nowadays made mostly either of glass (and Silicone sealant) or acrylic.

    But not just any container will do for keeping given livestock happy and healthy. Here are some general guidelines to help you in selecting an appropriate aquarium for what you intend to keep.

Modes/Materials of Construction:

    As stated, as long as the media your tank is made of doesn't negatively interact with the water, poisoning your livestock, aquariums can be made of most anything... A friend of mine actually has a fiberglass and resin sailboat in his backyard that he has filled with water to grow aquarium plants! The vast majority of aquarists opt for "store-bought" aquariums of glass and Silicone construction, though DIY projects of these and acrylic tanks can be bought or constructed on your own.

Size (and Shape) Matters:

    Bigger is definitely better when it comes to aquarium size. Larger volumes of water not only allow you more room to aquascape, space for your livestock to move, grow and interact, the bigger the tank is the easier it is to maintain and keep stable. Just like living near a large lake or the ocean, temperature is mediated by having or being near a large body of water. Chemical changes occur more slowly, and should there be a disaster, like over-feeding, a death, or power-outage, your margin of error and time for reaction is much enlarged with a bigger tank. All else being equal, freshwater systems should be limited to about one cubic inch of fish per 2.5 gallons of aquarium volume... Bear in mind the growth rate and likely ultimate size of the livestock you intend to keep, as well as their differential need for room for movement, temperament and psychological space... Many captive organisms are lost directly or indirectly for wont of room.

    Shape is just as important. Tanks that are lower and wider, as opposed to taller and narrower, have more surface area, and hence more room for gaseous exchange, horizontal room for the livestock to move around. Hexagonal tanks in particular can be limiting in the amount of life you can keep, though they can make spectacular displays for more vertical fishes like Angels, and slower fishes like Goldfish. As with most things in life, there are trade-offs in having more "show" style aquariums versus "breeder" shaped (low, flat, wide) aquariums. Taller tanks are more beautiful, but harder to maintain, with narrower range of safety should something go wrong.

Terrific Tiny Tanks:

    This is not to say that one cannot be successful as an aquarist with a small/er volume of water. Systems of a few gallons can indeed be kept, but these need to have more careful and frequent observation, care in feeding, and frequent partial water changes. Small volumes likewise impose limits on what types and how much livestock can be safely maintained. If space is at a premium for your proposed freshwater system, you will want to do extra research in its set-up, stocking and care... and be extra-diligent in keeping an eye on water quality... with new water at the ready to change out should troubles arise.