A lot depends on the Viv and the builder. Some are built with false bottoms, some drainage layers, some have backgrounds of spray foam, some use construction foam, others don't even use a background. It is possible to build a tank on a low budget. The 125 i built cost me about $50 in materials (not counting the tank). The plants however, cost more than everything else.
Education is the most powerful weapon we can use to change the world ~ Nelson Mandela