Definition of self sustaining
A self sustaining process or system is able to by itself without anyone or anthing else becoming involved.
reference: http://dictionary.reverso.net/english-cobuild/self-sustaining

Definition of an Ecosystem
Self-sustaining community comprised of interdependent organisms (plants, insects, animals) and their natural environment. It provides the food chain through which energy flows, and the biological cycles that recycle essential nutrients and wastes

reference: http://www.businessdictionary.com/definition/ecosystem.html

Our ecocolumn is self sustaining ecosystem according to these definitions because we are becoming involved after we constructed it and our ecocolumn is comprised of interdependent organisms and their natural environment.