My temperature rises and drops

[TeamTripleZero]

My tank is a 20g with 2 perc clowns and a bubble tip anemone. The temperature in the tank can drop to about 78 in the morning but rise to 82 at the end of the day. Well the temperature changes harm the fish and anemone? or should i set my heater to 80 and just not let the temperature drop below that so that the temperature will only rise 2 degrees.

 

[ThRoewer]

82°F would be the upper limit I would be comfortable with.
It's likely the summer temperatures in combination with the heat of the pumps and light that cause the rise in temperature. You could add a fan to cool the tank but it would require to refill evaporated water frequently.

 

[scumbag_gli]

I keep my tank at 81.3-81.7 all day everyday. My corals love it. The flux between 78-82 though is not great. I would invest in a better chilling or heating situation...try fans, if not, chiller may be your best bet