Allow me to relate a true story just for information!
by eethomp-at-welchlink.welch.jhu.edu (ELAINE THOMPSON )
Date: 8 Dec 1994
Newsgroup: rec.aquaria
Well, after the DIY coil denitrator stories that George and others
(sorry...I forgot who else) posted a few months ago, I should have known
better. But, I tried installing a Nitrex box in my 29g planted tank,
thinking that maybe something that was commercially available would work.
NOT! So here's my sad story that will hopefully convince you not to try
Nitrex.
I put the gadget in at the start of October. It's an almost sealed box
with a medium that is supposed to selectively grow denitrifying bacteria
and allow only a slow flow of water through. Nitrates did drop within a
couple of weeks to below 25 ppm--the bottom of my cheap test kit. Before,
they were between 25 and 50. Great, I thought. It works, and the algae
growth has slowed to a virtual standstill.
The problem? Fish diseases. After one round of killer Ick, one round of
bacterial stop-eating-hang-out-at-the-top-and-die-in-24-hours disease, and
two rounds of Columnaris, I had had enough. Water tested fine; pH 7.0, no
ammonia, no nitrites. And all of my other tanks have been WAY healthy.
What finally convinced me to yank the Nitrex box was when I added a new
clown loach from another healthy tank and he got Columnaris too.
So, I pulled the box out of the tank. I opened it up and was greeted by a
foul rotten-egg odor. So much for the Nitrex stuff not allowing
sulfide-producing bacteria to grow. Immediately, the fish looked
healthier, and that evening my angelfish ate his first healthy sized meal
in a while. The clown loach is healing up too.
The moral is: don't try denitrification. It's not worth it. Really,
it's not.