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Sintered Glass Diffusers - COMPARISON
I have recently had the opportunity to compare the ADA and
Eheim sintered glass CO2 diffusers. I have tried to note their
subjective qualities and also provide an objective note regards
their respective efficiencies. I have refrained from conclusions
recommending a particular product since I feel both are
sufficiently different, with different appeals. However I do feel
each product would benefit from incorporating some of the strengths
of the other.
So here are some of the issues, not in any particular order:
PRICE
If someone does not mind paying for the ADA label or desires
a product hand made by an artisan, than there is value in the ADA
product. But if the emphasis is on performance, the value is
clearly on the Eheim. More on performance below.
DURABILITY
The ADA is glass. I would like to believe it is durable glass but
than again I think glass can only be so durable. The Eheim is plastic.
I don't care if I drop it.
SPARE PARTS
The ADA unit is two pieces, the glass unit and the diffuser proper
(actual diffuser). The instructions indicate they are inseparable. This
implies if you break it, you buy a knew one. The Eheim is five pieces
without check valve. I do not know whether Eheim would sell spare parts,
for instance a new diffuser should the old one collect crud with use,
causing bubbles size to increase, reducing its efficiency.
DIFFUSER PROPER
The diffuser proper. The ADA diffuser does not come out of its
unit. This makes it harder to clean.
BUBBLE COUNTERS
The Eheim has an integrated one - mostly functional. Where it falls
short is that it must be placed (that is the whole unit must be placed)
in an area of the tank which is constantly visible. This goes counter
to the design of these items which is that they be unobtrusive. To
view the bubble counter, I had to place the Ehiem in the lower
front right side of the tank which from most viewing angles is
acceptable. Of course this may not be feasible in other tanks. Also
when I view the tank directly from the front, it is visible. For me the
bottom line is the unit is small enough that I do not mind.
To the extent bubble counters are necessary the ADA necessitates
an added purchase. ADA also necessitates the added purchase of a
check valve.
LONG TERM CO2 TESTER
If your into it, the Eheim includes one, the ADA does not.
TUBE DIAMETER
The Eheim is narrow and I believe metric. In U.S. measure, the outer
diameter of the Ehiem is 5/32in while the ADA is 9/32in. The Eheim tube
actually fits entirely _within_ the ADA tube. Of course the thinner
tubing
adds to making these devices less visible. A caveat for those with U.S.
tubing in the rest of their CO2 system is the need for an adapter. I used
a cheap Penn Plax from a LFS for the performance test. It seemed to work.
BUBBLE ZONE
I would like to suggest there are at least two items which contribute to
upper and lower boundaries of the bubble zone or area in which the CO2
absorption actually takes place. The upper bound is constrained by
bubble size with smaller bubbles decreasing the depth the unit needs to
be placed in the water column before bubbles can reach the surface without
being absorbed. This was a major plus with the ADA unit. (see below) The
lower bound is constrained by how deeply the unit can be placed in the
water column which gives bubbles more time to be absorbed before reaching
the surface. The Eheim is slightly advantaged here because the CO2 intake
is slightly shorter. The Eheim's thinner hosing (with its smaller bend
radius)
adds to this effect.
I noted that by locating the unit in a strong current within the tank, the
bubbles are given the chance to slosh around more, increasing their chance
to
be absorbed before reaching the surface. Locating the unit in a quiet area
of the tank caused an unacceptable number of bubbles to reach the surface
in the Eheim unit.
PERFORMANCE
This is as scientific as time and my only moderate scientific mind would
allow.
I was interested in measuring the amount of CO2 that got into the water
column
in a two hour period. The change in pH level was measured. (using LaMotte
test kit, accuracy to 0.2)
The following were held constant throughout testing:
A) air flow (main and fine needle valve remained unchanged)
B) bubble count (1 per second)
C) submersion depth of diffuser unit (9in)
D) KH (3.75)
E) light (kept off)
F) diffuser position within tank (front & center)
The following procedure was followed for each diffuser:
A) remove the diffuser from the tank and aerate
the water to pH = 7.2
B) turn off aeration
C) place diffuser in tank with the diffuser proper
located at a depth of 9 inches
D) measure pH drop for two hours.
The following pH changes were observed:
hrs:min ADA Eheim
0:00 7.2 7.2
0:15 7.2- 7.2-
0:30 7.2- 7.2-
0:45 7.1 7.2-
1:00 7.1 7.2-
1:15 7.1 7.1
1:30 7.0+ 7.1
1:45 7.0+ 7.1
2:00 7.0+ 7.1
Comments:
A) The bubbling in the ADA unit seems better;
that is, the bubbles seem to be more numerous and
small. Collectively, the ADA bubbles appear almost as
an effervescent cloud, their lightness causing them
to be pushed precariously by the tank's current. The
Eheim bubbles appear more as a determined stream,
their larger size helping to make a bee run for the
surface. Poetic as it may sound, precarious bubbles
are absorbed, bee run bubbles waisted. While the
bubbling in the ADA unit seems better, I was surprised
that the amount as measured did not show a larger
difference.
B) For both units, some of the bubbles were not absorbed
before reaching the surface. This was much more true with
the Eheim. This indicates that ideally the diffusers should
be located more than 9 inches below the surface. However
I note that pictures in the ADA setup guide show the diffuser
to be submersed only about 7 inches.
C) Both these units are designed for working pressures of
10-20psi and may have problems for CO2 systems whose
working pressure is significantly lower. This would preclude
their use with typical DIY yeast ferment style CO2 systems.
D) Finally, there is a note in the ADA instructions that for
bubble counts in access of 4 per second, the bubbles enlarge,
creating a reduction in efficiency
Christopher Coleman
christopher.coleman at worldnet_att.net