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Re: wet/dry filter & CO2 use

I questioned Tom Barr's statement that it yields higher CO2
efficienty to put the CO2 enriched water into the sump pump
intake and he replied:

> > What difference in efficiency does it make
> > to have the CO2 reactor output feed into the sump pump
> > suction side rather than go directly into the aquarium?
> Just a few:
> 1# Most folks want the CO2 junk out of the tank.

Okay, so you were not referring to external reactors.  that
clears that up.  My external reactors rarely clutter up my
tank.  I suppose if I dropped one into a tank --- ;-)

> 2# Returns from the main sump pump have far more flow and
> dispersion
> ability(Better mixing or CO2 enriched water into tank).
 Well I can put the CO2 water out flow in the tank and the
other sump outputs anywhere in the tank.  If I place them
intelligiently, the distribution and mixing won't be
measurably less efficient than run the reactor output to
the sump intake.

> 3# It's simpler than the the direct in tank method
Again, referring only to an external reactor in my case,
the hose has got to go somewhere.  The sump pump isn't any
simpler than the aquarium itself.  With a different type
reactor, could be different bu there's more than one way to
go without losing efficiency.

> 4# You lose less flow due to head pressure and tube
> length

Yes, if you the 'external' reactor in the sump.  We often
use strong pumps and throttling valves to control water
flow (up and down) on sup set ups, so the amount of head
isn't the kind of issue it is with canisters.  In fact, we
often need to add head to tune the system.  But if yo need
to reduce water flow resistance, shorter tubing and fewer
bends always helps.

> 5# Less potential for leakage (Everything is in the sump)
I can see this.  But good fittings also give you less
potential for leakage.  It's another way to go and it only
affects efficiency of CO2 use if you allow leaks to
continue unchecked ;-)

> 6# If the reactor capacity is exceeded, the sump return
> pump will give
> another stage to dissolve the CO2.

Uh, this one sounds like a stretch.  Bubbling free or
excess CO2 into the sump doesn't sound like a very good
reactor chamber.  But I'll admit I never tried this.  If
reactor capacity is exceed, either the CO2 flow rate is too
high or the water flow rate is too low.  Adjusting those
accordingly sounds like a better way to deal with
"exceeeded reactor capacity.
> > Is
> > this your recommendation for gravel tube type reactors
> or
> > all CO2 reactors?
> ? Now you are confusing me and yourself:-)
Well I try to do what I can and be democratic about it ;-)

> I think you are thinking about internal type reactors
> which are generally
> unsuitable for sumps since the levels vary and most
> reactors are often out
> of the water completely.
> Gravel vac tubes need to submersed which would mean the
> height of the water
> level would need to be equal to the sump level. This
> design would not have
> much directional output either allowing more mixing with
> the already rich
> CO2 water. This would reduce the effectiveness of the set
> up.

Well that was what I thought, but I was trying to figure
out your recomendation because it didn't seem to apply to
my situation.  I'd like to conserve CO2 use but I didn't
see how the change in routing could help. ;-)
> You want to have the CO2 poor water come in, have CO2
> added, returned to the
> tank without any mixing. Feeding the reactor's output
> directly into the sump
> pump's return does this. Most folks have their return in
> the form of a
> downward pointing spray bar or output with far more
> current than the CO2
> pump's flow.  

But taking the output tube from the reactor to the
aquarium, I submit, works just as well as taking it to the
sump.  I wish it didn't.  I'd have any easy improvement to
make in conserving CO2.
> > With an external reactor, I don't see why feeding
> directly
> > into the tank would be less efficient.
> See above. If you want to have an external reactor with a
> powerhead in the
> tank, 

Naw, I just use a feed *from* the sump pump manifold; Its
input is connected to the sump pujp output.

>well I suppose, but a well designed sump style
> reactor has far less
> flow restriction, there is no return tubing that needs to
> come up and return
> back into the tank, the sump style reactors simply fall
> out the bottom and
> have a directional output. Very little backpressure is
> produced with this
> design, actually, the minimal possible amount and still
> have directional
> output. 

If I knew what kind of reactor you were talking about, I
wouldn't have written so much (about this ;-)  )  One can
see this design in Erik's That Darn Planted Tank on the


A web page that still makes me want to go out and buy more
acylic than I can afford just to make some of the stuff
Erik did.  It's a very good way to go.  But backpressure
isn't always an issue; sump pumps are often 'oversized' 
with throttling valves to allow control over flow rates. 
Even Erik's example talks about going down form 3/4 to 1/2"
tubing as I recall to increase the head and allow the
throttling valves to be farther open (I think to avoid
cavitation in the valve but I could be misremembering).

So I see reduced backpressure as the advantage.  But I
don't see it as an imporovement in CO2 efficiency.  But I
could be wrong, or so I've heard.  I'll move my reacter
over to sump and point the output into the sump intake (the
recycle loop) and see if I measure an improvement in CO2

I'll post the results if there is an improvement.  I am
hopeful but dubious.  Reducing the total overflow water
turnover rate will probably have the greatest effect on CO2

As for energy efficieny, sumps aren't the best way to go in
that regard, too much tubing.  An in-tank or hang-on-back
filter uses very little tubing.  Even a canister is
probably more energy efficient since you don't lose all
that energy form water splashing down the drain tube.  

Thanks for the info and the patience,
Scott H.

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