Would cold temps kill dinos? algae?

[Reefs and Geeks]

Sort of an odd question, but if tank water were to drop to say 65F, would that kill off any undesirable algae/dinos/cyano...etc? I just did a water change on my display and saved the old water from my tank and have it in my basement, which has been down to about 65F. I was thinking I might use the water to cycle some dry rock to build up some good bacteria while I finish up some plumbing, but don't want to use the water if it's going to cause some sort of algae issue on the new dry rock before the bacteria has a chance to colonize it. I will of course warm the water up to normal tank temps for the bacteria, but was curious if the water being cold for a day or two would kill any free swimming stuff from the water.

 

[EmdeReef]

Sort of an odd question, but if tank water were to drop to say 65F, would that kill off any undesirable algae/dinos/cyano...etc? I just did a water change on my display and saved the old water from my tank and have it in my basement, which has been down to about 65F. I was thinking I might use the water to cycle some dry rock to build up some good bacteria while I finish up some plumbing, but don't want to use the water if it's going to cause some sort of algae issue on the new dry rock before the bacteria has a chance to colonize it. I will of course warm the water up to normal tank temps for the bacteria, but was curious if the water being cold for a day or two would kill any free swimming stuff from the water.

The short answer is no.

Dinos, cyano etc are one of the true cosmopolitan species found in all oceans from pole to pole. Much lower temps could slow down the metabolism etc.