"Tony Volk" wrote in message
...
I used to do the DIY yeast CO2 injection directly into the uplift tube of
my
HOB filter for my 39 gal tank. With that setup I was able to achieve
about
18 ppm CO2 saturation. I found that I could get a good 8 days of
production
from a 64 oz mixture (juice bottle) and so I would change the mixture out
every weekend with a new batch that was started 24 hours prior (new batch
usually mixed up on Friday night). That way, every Sat or Sun the
aquarium
got a new charged up batch of CO2 that *could* last 8 days.

Thanks for the replies everyone. How long did you inject into your
filter input tube? I've heard that the bubbles can play havoc with the
filters propellers and rubber fittings, plus they make more noise. But
that
most mostly with injecting directly into the input and skipping the tube
(at
least, that's what I remember reading). That was one of my first
instincts,
but I'm cautious about damaging the filters. On the other hand, did you
notice if the increased suction from the filter input had any negative
effects (e.g., did it ever suck any fluids from the CO2 canister when its
pressure dropped towards the end)? Cheers,

Tony

p.s.- I've been calculating my water changes based on tank size- is that
correct or should I calculate the % based on the actual volume of water in
my tank (e.g., my 55 gallon tank probably only has about 45ish gallons of
water, so a 30% change is actually a 35% change, etc., meaning I'm
changing
35-40% of the water each week-closer to Tom's suggestion).



You should calculate the volumn based on your actual volumn. E.g. (total
volumn - substrate etc) * 35%.

I'm not exactly sure of your question regarding the HOB intake tube and the
DIY CO2 injection... What I did was rubberband the air hose (coming from
the DIY CO2 juice container) to the intake tube of my AquaClear filter so
that the opening of the air line tubing was just below the intake. I'd also
cut the airline tubing so that it was at a 45degree angle. By putting the
angle cut side toward the intake tube the bubble would come out right next
to the strainer on the intake tube and that would help insure that the
bubble was sucked up into the filter. I never had any problem with the
filter at all. There was an audible "crashing sound" as the bubble was
smashed by the impeller. I also kept the water in the tank very high as to
accommodate the return from the filter so that there was not a lot of
surface agitation (I think you mentioned that you were already doing this).
When the DIY yeast mixture was due to be changed out, I simply unscrewed the
juice cap (with the tube coming out of it) and screwed it onto the new DIY
yeast mixture in the second juice container. Worked great.

HTH,

Djay