God bless temperature controllers. I have three of them I built myself. They have a 4" 3 wire RTD for accurate temp. sensing, and control to less than +/-1F. The readout is 0.1 resolution. The one in my discus tank controls two cheap as dirt penn plax non-submersible heaters (total 250 watts) at 86.5 deg. F. Another heats the holding tank (25 gal. garbage can) water to 87 deg. F. Total cost of parts ~ $30.
