Re: [APD] CO2 and pH control

["David Grim" <grim1214 at bellsouth_net>]

Gordon wrote:
>
David,
    I really appreciate your taking the time to provide such a thorough
response to my question.

    Yes, you are correct in assuming that this was once a reef tank. And
you're also correct that my filtration system is probably overkill for a
29 gallon tank, but I like to tinker - what can I say? The filter is a
modified RDP filter with a bioball tower added (no current RDP
fiunction) There is a 3 gallon glass chamber filled with Dupla bioballs
beneath a perforated drip plate covered with poly fibre quilt batting as
a coarse filter all sitting on top of the sump. The tower has a tight
fitting lid. I debated adding the trickle chamber but after reading
George Booth's articles on the subject, concluded that trickle filters
were not a significant source of CO2 offgassing, although I'm guessing
that's a debatable pointn.

    The tank upstairs has a corner overflow and because of its location
(built into a living room wall) I don't have many options besides the
remote filter. I could remove the tower and just use the sump but I
would still have the waterfall effect in the piping.

    The tank is covered with a home made cover with 2 PC bulbs suspended
2 inches above the water. The ends of the cover are open for ventilation
so I would consider it an open top tank.

    HOB filters are not an option nor are canisters unless they are used
at the sump.

    The SMS122 controller is new and I calibrated it to 7.2 upon setup a
week or so ago. The reading correlates with chemical pH tests so I'm
confident in its accuracy.

    Regarding the AAS atomizer, it's really just a misting wand for a
drip irrigation system and while it's a handy way to have inline
injection, I question its efficiency. Do you think I could gain anything
with say an external Aqualogic reactor or one of the membrane types or,
with the amount of offgassing it sounds like I have, am I doomed to have
an inefficient CO2 system?

    On the other hand, others have pointed out that if I've got good
plant growth and happy fish, which I have, I should be satisfied and
quit worrying about pH levels. Am I trying to micro-manage too much?
>

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:
http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=3662&N=2004+22777

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.

Regards,
Dave






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