On Sat, 18 Feb 2006 23:40:44 -0600, dc wrote:

"Altum" wrote in news:1140286709.246608.305140
:

the smell of a healthy, mature filter. Am I the only one who "tests"
water chemistry by sniffing it?

Nope, you are not alone. With more than 260 tanks to look after, small is
often my first clue to a new potential problem when I walk into the fish
room in the morning. I will often follow my nose to the trouble spot.

Ammonium, nitrite, and nitrate all have their own distinctive smells.

I agree that one can tell a lot about a tank by sniffing it. Like good
garden soil, a healthy aquarium has a distinctive and wonderful smell.
I generally give each of my tanks a quick sniff during the morning
feeding. The fish get to look at my nose before they get their
breakfast. And the warm moist air clears my sinuses.

-- Mr Gardener