My tank had a temp swing of 3-4 degrees on a normal day with my drop in chiller. When it gets hot here, my house becomes an oven, and the tank would heat up above 82. With the in-line I just got, it stays at a constant 79, no matter what. Now my house is old, so it has single panned windows, and no freaking insulation, thus the need for a chiller here. I tried the fan route, both on the tank, and on the sump (at the same time) and could not control my temp. This is why I say "only you know" if a chiller is needed for your system.