When you immediately sample two diff volumes of water right
next to each other, it's not hard to judge whether they are
within a few degrees of each other. And it's pretty clear
that that is plenty close enough for fish and plants. The
consistency in temperature sense perception is pretty good
over very short intervals of time.
Otoh, if you are setting the water temp at a sink that is
some distance away from the aquaria -- about 30 feet in my
case -- then temperature perception can be much farther
off. Rather than running back and forth from the aquaria to
the sink and vainly hoping that my temperature sense memory
is doing a remarkable job, I just set the faucet flow for a
specific temp, give or take a few degrees, then carry the
hose outlet to the aquaria and fill.
Depending on the size of the hot water supply and the
amount of refill water needed, the temp can remain
reasonably constant after being set or can steadily decline
as more water enters the hot water heater. This is probably
only an issue if one is filling very many gallons of
aquarium water, ay maybe 100 or more gallons.
Of course, anyone that's ever come into the house after
spending time outside on a cold winter day, and then put
one's hands under a flow of tepid water, knows that a
human's ability to judge specific temperatures is subject
to considerable vagueness.
If I spend $50 or more each year on CO2 and maybe half that
on fish food, then considering saving two or three dollars
on a thermometer doesn't occupy much of my purchasing
decisionmaking. Alas, I am a victim of the theory of
marginal utility -- or maybe not a victim, maybe i just
surrendered ;-) . I do not dismiss frugality as virtue, but
like yogurt, it's a matter of taste and economic
I know longer use buckets to perform water changes because
it was just to perturbing to look into those white buckets
and wonder what color the water was ;-) .
For a similar reason, I have left off using straight pins
and their confounding head-size as measured in
Completely unrelated to my pinhead thinking, I ask, how
many folks actually enjoy water changes? Is it not still
the number three least liked part of maintaining fresh
Have plants, have fish, have a ball,