Temperature Swings

[gkersten]

How much of a temperature swing during a 24 hours period is acceptable . My 185 gal tanks presently runs 77.5 degrees at nite but once the MH lites kick in and temp of the day increases the temp in the tank goes up to 80.5 . Is that degree of swing acceptable or should I consider buying a chiller. If a chiller was used what variation in swing would I expect