Correct parameters and stability of those parameters is the key to success in this hobby. If I constantly fluctuate the heat in your home you will get sick. If I turn off the heat in the winter (assuming your north of the boarder ) you will get sick.
Stability is best for long term success...
Wow....I. amazed people still believe this old wives tail. Temperature fluctuation does not make you sick! Absolute rubbish. Viruses, bacteria, and other variables make you sick! Not temperature alone. In the winter my house hits 60 degrees, and warms to 75 with the wood stove. Summer time my house hits 80,and 60 when I sleep with the air conditioner..going into the beer cooler at the distributor and back to the summer heat does not cause illness. Cmoon seriously!!!
Not sure where I refer to slight variations. After 5 degrees change in a short period, this is what I am referring to.
Instability in temperature and environment surves to add stresses to our body and reduce immunity, thus setting up an environment for which the virus's you speak can take hold. It is not unlike ICK. ICK is defended by having strong healthy fish with limited stress. Even an infected fish can rid itself of ICK provided stress remain low and food intake up.
While temperature is not the cause, it is one important factor in the creation.
So like I was saying, consistency, reliability and stability is the key learning and is the difference between a reef and a great thriving growing reef bio-sphere.
So, C'mon this is the foundation of reef keeping, or at least mine.