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Bio Wheel Co2 Outgassing ? Lots!
Hello APDers,
One of my setups is a 55g heavily planted tank with a high-fin cobalt and a
red-turquoise that look like they want to pair so I moved them to the plant
tank that has been up for about a year. I have a magnum 350 with 2
bio-wheels, pH 6.8-7.0, 0 ammonia, o nitrites, <10ppm Nitrates most of the
time. Co2 injected fine gravel with Dupla laterite (balls) in the substrate
and
occasionally I add Jobes plant sticks for ferns & palms in the substrate if
I see slow grow. All plants are doing very well except when I forget to add
some Ca/Mg every couple of water changes. I use Kent Fresh Water Plant food
with good success. 4 tubes, 160 watts florescent with a mix of
tri-chrominic 50/50 and GE Chroma 50 Daylight bulbs. I have compressed Co2
with a good diffuser from Aqua-Direct. (I really like this setup and it
comes with a magnetic valve, 2.5lbs. bottle, a great fine needle valve and
efficient diffuser for about $250 bucks).
Anyway, a while back I posted a question about bio-wheels and their effect
on out-gassing Co2. The consensus seemed to be that if the tank water is
kept as high as possible you could minimize the return water agitation and
therefore minimize Co2 out-gassing. This seemed like a logical
interpretation and I maintained my water levels as high as possible. With
discus and water changes every 3rd or 4th day this was no problem.
With the bio-wheels in place I would have to use in the order of 2-3
bubbles/second to maintain the pH just between 6.8-7.0 and Co2 between 15
and 25ppm. Even with water out of the tap at pH 6.9, kH 1, gH 2 it seemed I
need to use an inordinate amount of Co2. I would add baking soda to raise
the kH to 4.
Taking my own challenge to test what would happen if I remove the bio-wheels
I almost killed some fish!
The night before last, after removing my bio-wheels, creating a home-made
spray bar situated 3-4" below the water surface (absolutely no surface
movement), I reduced the Co2 to about 1 bubble/second and measure the pH
before going to bed at 6.8. I awoke to find my fish breathing rapidly, a
couple of tetras at the surface (which I have never seen) from either too
much Co2 or not enough O2. My feeling is that maybe both occurred! My Co2
test kit was out of commission but the pH was down at 6.2/kH 4-5 = Co2
between 75 -100ppm . YIKES! I turned the outflow from the Magnum almost
vertical (like a pond fountain) to maybe get some O2 in and get some Co2 out
of the tank. This obviously worked fast, maybe too fast. The pH was back
up to 7.0 and kH actually went up to 6 (?) in a couple of hours.
So I set the bubble rate to about 1 bubble/3 seconds throughout the next
day. With the plants taking in Co2 throughout yesterday I'd reach a stable
pH at 6.8. Funny thing is that my kH also rose from a consistent and
normal 4 to 6? Don't get this yet.
Not sure of my O2 saturation rate, so last night I set an air stone up
(please no flames, please give me time to figure this out), on a timer to
come on an hour after the lights go off and then to go off an hour before
the lights came on this morning. Co2 remained constant at 1 bubbles/ 3
seconds throughout the night with the air stone going. The pH the next
morning was 7.5 because of the air stone but by mid noon and air stone off,
the pH was back down to between 7-7.2 & kH 5 which equates to about 10ppm
in the pH/kH tables.
Well as luck would have it that my LaMont Co2 test kit refill arrived today
UPS at noon from Pet Whorehouse (intentional, they back-order my ammonia
test kit aaarrrgggg!), and I tested about 15ppm Co2, I increase the Co2 rate
to get between 20-30ppm by mid afternoon, pH 6.5 and has been stable ever
since.
Later in the evening the pH seems to have stabilized at 6.8 with kH 5 =
23ppm Co2 from the pH/kH tables and this coincides with the LaMont Co2 test
at ~25ppm.
If you haven't deleted this message by now my question is.....Tonight I will
not use the air stone. How do I know I will have enough O2 to last the
"lights out" period when photosynthesis is not occurring and the plants are
actually respiring more Co2 (also causing a pH drop)? I don't, I will
find out in the morning......STAY TUNED.
The message here is that up until now I was really not seeing the dramatic
effect a good Co2 system can have on pH because of the Bio-Wheels
out-gassing so much Co2. IMHO Bio-wheels eat up a lot of Co2, probably
more than most people think and even if they are not splashing about.
Oh yea by the way, don't get me wrong I love the bio-wheel's ability to
maintain colonies of cycling bacteria, they work great, just not on planted
tanks (no mystery here). The interesting thing is since removing the
bio-wheels I have only noticed a slight .25ppm spike in nitrites yesterday
and by this evening nitrites are undetectable !! I can not test ammonia but
the fish look fine, the pH is below 7.0 so if anything the plants are
utilizing the non-toxic ammonium (a great and free plant fertilizer) and I
will do water changes every day till I get one. Time will tell.
I know, run right out now and get a $900 pH controller (maybe for the new
125g I am setting up?). With the reduced bubble rate and no air stone do
you think I will have enough Co2 to make it till dawn ?. Will my fish still
love me in the morning? Anyone have some kind words of wisdom here.
Conclusion:
* Bio-wheels (with spray bars like the Magnum) cause a substantial amount of
C02 out-gassing
(plus snails clog them).
* I am partially convinced that people on the list that say heavily plated
tanks like mine can handle the increased bio load are correct. Even with
moderately-fed discus (beef heart) I have not seen any increase in nitrites.
Could it be that my nitrites are immediately being converted to ammonia (for
which I have no test kit, dumb I no)?
More as it happens.
Enjoy,
Tom Brennan
brennans at ix_netcom.com