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Re: [APD] CO2 and pH control

Using overflows with canister filters can be tricky. With a
sump, changes in total system water volume are accomdated
by changes in the amount of water in the sump. Wihtout the
sump, the overflow has to handle the changes in water
volume (e.g., from evaporation) and the overflow generally
can handle only much smaller volume changes than a decently
sized sump. So one needs to keep an eye on the water volume
more closely than with a sump.

The big advantage is, Dave pointed out, you can acheive a
slower rate of shedding of CO2 by avoiding the trickle
chamber and avoiding the gas/water turbulence of an
overflow drain into a sump.

I too was able to reduce CO2 loss by removing the trickle
chamber and installing a Stockman standpipe but the CO2
consumption is still much higher than I had with a


--- David Grim <grim1214 at bellsouth_net> wrote:

> > Gordon,
> My experience with the 240 gallon planted tank (Oceanic
> 240 reef ready) with
> wet/dry filtration tells me that the more water movement
> you have the more
> off gassing of CO2 you have. I have not read George's
> articles on it. My
> experience is purely anecdotal. All I can say is that
> conditions being
> constant except going from wet/dry filtration to canister
> filtration in a
> planted tank, with the resulting decrease in water
> movement/sloshing/splashing/cascading/bubbling, etc., the
> pH of the tank
> lowered to my target level, and the controller cycled off
> for longer
> periods. I just plain used less CO2 and the pH was easily
> controlled vs.
> using CO2 in a wet dry with the controller on all the
> time. This using the
> same internal CO2 reactors with both setups. Tinkering is
> great. That is how
> I set up a completely automated water changing system
> that services a 265,
> 240, 75 and 120 gallon tank.
> If everything is cool and you like the plant growth, etc,
> then you could
> just leave it status quo. I never liked not being able to
> keep the pH where
> I wanted it, because it never seemed a problem for other
> planted tank
> keepers. And my water here in Atlanta comes out of the
> tap with a GH and KH
> of less than one. The best I did with the 240 planted
> with wet dry
> filtration was 6.8-6.9, where I wanted to have it a bit
> lower, like 6.5-6.6.
> This was with two reactors, each with a 20# CO2 tank
> feeding it. Assuming
> that there is a relationship between water movement in a
> wet dry and CO2
> loss, there are a few choices for you:
> Lessen water agitation within the tank and the  wet/dry
> system: I pulled the
> bioballs out of the wet dry and plumbed a barbed fitting
> under the tower
> cover and attached a piece of vinyl tubing which made the
> water enter the
> wet/dry enter below the water level in the sump, which
> lessened the
> splashing. This removed the bio filtration of course, but
> it is really not
> needed in a planted tank IME, and eliminates another
> source of water
> agitation and possible off gassing. You could add a
> submerged sintered glass
> media or an air driven Hydrosponge in the sump to have
> some backup bio
> filtration if you want it there for peace of mind. I use
> Hydrosponges in the
> sumps of my bare bottom Discus tanks. I covered all open
> areas of the tank
> and the wet/dry to try to keep as much gas from leaving
> that way. Point the
> water return downward to reduce any surface agitation.
> All this should keep
> CO2 in the water longer.
> Add an in-tank CO2 diffuser: The Dupla unit I mentioned
> would be good for
> your tank, unless the combined volume of your sump and
> aquarium are more
> than the unit is rated for. Just keep the small size of
> the tank in
> consideration, as aesthetically a large in tank unit
> might be ugly. The AAS
> in line unit just doesn't work well enough.
> Do both of the above and you may see improvement.
> There is another option for you where you can pull the
> wet dry altogether,
> but keep the same overflow and location of the filter (in
> your basement):
> You can use a closed type canister filter with an in-line
> pump to return the
> water from the basement to the tank above. Look at his
> URL:
> Your prefilter will work the same, except now there would
> be a constant
> level of water in the tank. Your corner overflow would be
> filled with water
> to the top. The water level is determined by the level in
> the tank now and
> not the level in your sump. Your setup is now a closed
> water loop like a
> canister filter setup is, except the overflow plumbing
> from the prefilter is
> now completely full and the water is not splashing
> anywhere and there is no
> CO2 loss from water agitation. Evaporative loss is now
> shown in the tank
> water level and not the sump water level. You could
> probably inject CO2 into
> the filter intake and not need an internal reactor with
> this setup since you
> have eliminated the agitation.
> This method is not cheap, but would probably solve your
> problems and
> wouldn't interfere with the installation setup of the
> tank itself.

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