#glue

I’m rescaping my tank by useing some of the rocks that are already in the tank, what is the best glue to aquascape with/ the cheapest.

I am planning on rescaping my 1 year old set up.I will be breaking the rocks already in the tank, so should I be using thin or thick glue when scaping? If thick, what export would you guys recommend or would you recommend not using any epoxy at all