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RE: [Killietalk] filter
Chris <cgraseck at optonline_net> wrote:
Just wanted to comment on the use of trickle filters. Let me preface my
comment by saying that this is in no way meant to be a criticism of the
de Bruyn style filter, but some of the people who are newer to this may
not know the other side of the story.
Trickle filters are extremely efficient at stripping ammonia/ammonium
from water. In doing so they are, in effect, nitrate factories.
Nitrate is less toxic than ammonia but is still toxic (Charles may
So does Wright, as much as it deeply pains me to be on the same side of
*any* argument with Charles. :-) [We get our jollies by flaming each other!]
Nitrates at several *hundred* ppm have been shown to be totally
non-toxic. Many plant nuts have to *add* copious amounts of nitrates to
keep their aquatic gardens growing and looking good. 30-50 ppm are
typical minimal needs for a CO2, high-light tank. Gross overdoses don't
seem to bother the fish.
An intermediate product of nitrification, nitrite, *can* be lethal as it
ties up the hemoglobin oxygen sites, mostly at lower pH, and suffocates
fish. IDK if it ever shows with a deBruyn filter that also has
illuminated plants in the tank. If it does, a bit of added salt can
quickly fix it.
The point is that you still have to change the water as the
nitrate builds up. Plants can utilize nitrate but not as easily as
The difference was once argued, but has been shown to be a part of
aquarium mythology. The chemistry logic is impeccable (energy
arguments), but, in practice, plants use nitrates very easily, indeed.
Ask the folks on the Aquatic Plants Digest.
By quickly converting ammonia/ammonium to nitrate the
plants are in effect robbed of their chance to scavenge that
ammonia/ammonium for themselves. Nitrifying bacteria oxidize
ammonia/ammonium and nitrite to produce nitrate. Plants metabolize
ammonia/ammonium in the manufacturing of amino acids. There is no
byproduct, well I guess there is water produced as the peptide bonds are
formed. Lets say there in no nitrogenous byproduct ;-) Trickle filters
are also efficient at stripping dissolved CO2 from tank water which may
leave your plants lacking a carbon source (depending on the amount of
light available, of course.)
Not even a faint problem in most killifish tanks, IMHO. A *good* trickle
filter needs lose an insignificant amount of CO2 as it adds lots of
oxygen to the tank. [The two aren't mutually exclusive.] Only a lot of
splashing and agitation (like shaking a Coke) will cause CO2 to leave a
supersaturated solution. There is essentially none of that in a deBruyn
filter, unless the airlift tube is poorly designed. Usually, it is as
gentle as pouring your Henry's (not Henri's) against the side of the
If CO2 isn't being injected from outside, the amount of CO2 should be
*higher* with a good trickle filter as it increases the air interface to
allow equilibrium to be approached, even closer. [Just guessing. Never
have tried to measure such subtle level differences.]
Based on pH behaviour, I'm almost certain it cannot *lower* CO2 below
equilibrium concentration with the air.
Trickle filters certainly have there place but I find that a sponge
filter, which is slower to consume ammonia/ammonium in combination with
rapid plant growth works well and is not as complicated. An added sprig
of Pothos rooted in the tank water adds greatly to this affect.
Henri's original thinking was based on the planted sumps his father had
out in the yard to denitrify his fishroom. They were filled with emersed
plants to do exactly what you suggest. Henri apparently found the plants
less useful than the wet lava rocks, in his early experiments. I
certainly prefer having my plants *in* the tank.
On the other hand, if you are looking for a project and want the extra
dissolved O2 + evaporative cooling than go for the trickle filter. Be
careful of the extra humidity though :-)
Not a problem here. Our high-desert air (5-10% humidity) dictates the
use of swamp coolers, anyway. The uncrackling of our aged reptilian skin
actually feels pretty nice. ;-)
Please be aware, Chris, that your objections are right on for many of
the truly bad designs I have seen at the LFS being sold as "trickle
filters." My practical experience with the deBruyn design is what I base
most of my objections on, above.
Water changes would still be mandatory, even if every atom of nitrogen
was removed with the plant cuttings. *If* you have active photosynthesis
working, and *if* you have high oxygen, the changes can maybe be delayed
quite a bit with little visible effect. That was Henri's desire, as he
often went between FL and Belgium and needed a way to delay water
changes while away. Long term, though, I'm not convinced you can
eliminate them, even when the plants drive nitrogenous compounds to near
zero (as has frequently happened in my high-light planted tanks).
I'm not a big believer in the mysterious anti-growth pheremone build up.
I think it is more likely that a really healthy tank just selectively
uses up traces of heavy metals and other essential nutrients. Their
absence can stop growth dead! [Tap (not RO) water replaces them with
[I base this partially on seeing how people damage their fish by abusing
RO water or rain water. Looks way too much like failed water changes to
just be ignored. :-)]
Building a bigger flame shield as you write! ;-)
Wright Huntley - Rt. 001 Box K36, Bishop CA 93514 - whuntley at verizon_net
Eschew obfuscation and bloviation!
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