Either strong inert plastic or fibreglass is recommended because of their durability and
long life span. Metal is not possible because of rust. Plastic and fibreglass are convenient
to install (also for plumbing) and are fairly light and manoeuvrable. Animal-watering
troughs are commonly used, as they tend to be cheap. If using plastic containers, make
sure that they are UV-resistant because direct sunlight can destroy plastic. In general,
low-density polyethylene (LDPE) tanks are preferable because of their high resistance
and food-grade characteristics. Indeed, LDPE is the most commonly used material
for water storage tanks for civil uses. Another option is an in-ground pond. Natural
ponds are very difficult to manage for aquaponics because the natural biological
processes, already occurring within the substrate and mud at the bottom, can be hard
to manipulate and the nutrients are often already used by aquatic plants. Cement
or plastic-lined ponds are much more acceptable, and can be an inexpensive option.
In-ground ponds can make plumbing operations difficult, and the plumbing design
should be carefully considered before embarking on this option. One of the simplest
fish tanks is a hole dug in the ground, lined with bricks or cinderblocks, and then lined
with a waterproof liner such as polyethylene plastic. Other options include secondhand containers, such as bathtubs, barrels or intermediate bulk containers (IBCs). It is
very important to make sure the container has not been used previously to store toxic
material. Contaminants, such as solvent-borne chemicals, will have penetrated into the
porous plastic itself and are impossible to remove with washing. Thus, choose used
containers carefully, and know the seller if possible.