what fertiliser should be given to bonsai and how can it be keptshort in height please advise is there any harmone powder used to keep it short?

My dad used to do Bonsai trees. I seem to remember him clipping the roots on a regular basis to keep them small. No idea what he fed them though.

You need to prune them regularly and trim their roots once a year, preferably in spring, and repot them is necessary.
Give dilute liquid fertilizers, when the plant shows growth, avoid chemical fertilizers as we do not want vigorous growth.

You can also order Bonsai food. The granular type and you sprinkle them once a year. It is released slowly when watered and is great.