fw:HELP! High CO2

Here's a message from stevensj.

From: stevensj at calshp_cals.wisc.edu
Received: by calshp.cals.wisc.edu;
          id AA299365705;; Tue, 11 Jul 1995 13:01:45 -0500
Message-Id: <199507111801.AA299365705@calshp.cals.wisc.edu>
Subject: HELP! High CO2
To: AQUARIUM%EMUVM1.BitNet at wigate_nic.wisc.edu (Fish and Aquaria)
Date: Tue, 11 Jul 95 13:01:45 CDT
Cc: aquatic-plants at actwin_com
In-Reply-To: <25071112252335 at WISCMACC_BitNet>; from "Bob Mankin" at Jul 11, 95 10:24 am
Mailer: Elm [revision:]

Hi Everyone,

I posted a message to the aquatic-plants list this morning regarding
high CO2 levels (>40 ppm La Motte) in my 25 gal tank this morning. 
I thought I had the situation under control when I left this morning
after disconnecting the DIY CO2 system, doing a couple of partial water
changes (30%) and lowering the water level to get more aeration and
CO2 levels <30 ppm.

The fish had been hovering at the surface this morning & i removed the
clown loach which was lying still at the surface & put it in another
tank & it recovered activity.  The fire-eel & kuhli loach which had
been hovering at the surface but were too active to catch were not
at the surface anymore when i left.  I had lowered the CO2 levels to
below 30 ppm with water changes & aeration.

But ... I came home at lunchtime & found the tank looking cloudy,
CO2 >40 ppm again and the fire-eel & angelfish dead, kuhli loach,
3 corydoras catfish & two small guppies (the only other tank 
inhabitants) still alive & quite active.

I wondered if maybe the tap water I used to do the water change (since
I had no RO water on hand) had caused the cloudiness. I had used
Tetra Aqua Safe One Step chlorine, chloramine, toxic ammonia remover.
I added a polyfilter to the tank & changed one of the carbons in
one of the two aquclear 150 powerfilters.

The pH is 7.0-7.2, as it was this morning.
Nitrites were zero this morning, now it is 0.25ppm
and ammonia was zero this morning, now it is 0.1 ppm, presumeably
due to my excessive waterchanges which upset the biological
filtration, or possibly because high CO2 killed bioloogical filtration
and/or fish, elevating these levels.

I removed the dead fish & tried to catch the remaining fish but could 
only catch one of the corydoras catfish (it is a heavily planted tank).

Please could someone help me figure out what's going on & how to
fix it.

The only change to the tank recently was a 10% water change on Sunday
using tap water that had been soaked in a bucket with peat for 2 days
and addition of a large aponogeton (elongatus) plant from another tank.