What colour septic tank should I choose?

There is a belief that black IBC tanks are "better" than white ones.  When the IBC tank is being used as a septic tank then this simply isn't true.

A black tank will greatly reduce the amount of light that passes through it.  This is useful if it is being used to store clean water, as algal growth will be reduced or eliminated inside the tank.  Algal growth in a septic tank is not a problem, and as most situations involve burying the tank underground this rarely occurs anyway, regardless of the colour of the tank.

The black tanks that we use have a wall thickness of 4mm and are 2-ply, made up of an outer black layer (ply) and an inner white layer.  Our white tanks are single-ply and have a wall thickness of either 5mm or 6mm, depending on availability.

Generally, we would recommend a black tank only for an above ground installation, purely because you cannot see its contents, and a black tank my blend into its surroundings better.

In situations where the tank will be buried we would strongly recommend a white tank as they are cheaper and benefit from thicker walls.