Active control of Rayleigh-Benard convection in small aspect ratio horizontal layer, by perturbation of the lower thermal boundary condition, is shown. These experiments use a novel shadowgraphic system to measure the departure of a high Prandtl number fluid from the no-motion state. A proportional control scheme uses the shadowgraphic information as feedback to determine the lower boundary heat flux distribution. An array of individually controlled heaters imposes the heating distribution. Significant suppression of the convection amplitude is possible to at least 10 times the critical Rayleigh number. This convection control method provides an economical alternative to magnetic convection suppression.