Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
It probably depends on the fish. Research your fish species, and the water they originated in.
Most tropical bodies of water will overall stay warmer than temperate water, but there still may be a change in temperature with the seasons.
Not always related to what we think of as summer or winter in temperate zones, though.
In the topics there is a 'rainy season' and a 'dry season', not really summer or winter.
During the rainy season the water may be cooler, and softer (fewer minerals, lower GH, KH, TDS) if the rain is diluting the water.