"Sean Dinh" wrote in message
...
Hi George,

the only major problem I see atm is hydrogen sulfide gas.
You would need a serious degassing tower to remove it fast.

I have rocks and kitty litter in my pond. I'm hoping the 3
Dojo Loach are digging around there to reduce hydrogen
sulfide gas accumulation.

As for nitrate reduction, the simplest is to use a 4' tall
Trickle Tower outside the pond. Since you don't have any
plants in your pond, you won't worry about TT being too
efficient in removing nitrate. Only people like me worry
about having too little nitrate for our water plants.

I do have plants in my pond. I have lillies, irises, and cattails. I don't
have room for a veggie filter. Trickle towers have been shown to produce more
nitrates than they digest (they aren't actually designed to digest nitrates
anyway, contrary to some advertisements seen on aquarium supplier web sites.
They were designed for CO2-O2 gas exchange and to provide a habitat for nitrite
and ammonia reducing bacteria, which tend to convert these compounds into
nitrates), which is why marine aquarium enthusiasts are moving completely away
from them and any mechanical filtration. As for hydrogen sulphide gas buildup,
it is true that this could be an issue. However, if oxygenated water is blown
over the sand bed and around the reef, and one periodically stirs it up, it
shouldn't be too much of a problem. It doesn't seem to be a problem in marine
aquariums, which tend to produce more gases than freshwater environments. The
key is not to let the sand bed go stagnent. Since the bacteria that will be
living in the sand bed and in the water will break down any detritus very
rapidly, and because sand is very porous , any gases produced will out-gas and
be washed out by the water flowing over the sand at a slow rate and be exchanged
in the main filter and on the waterfall with oxygenated water. In addition, the
sand will become a habitat for lots of critters which will no doubt continuously
bore into it. This is good, since it will disturb the bed and help keep it
oxygenated. In addition, since many of these critters reproduce rapidly, the
fish will root around in the sand bed looking for a tasty meal, disturbing the
sand bed even more, adding oxygen to the sand, and reducing the cost of fish
food. All of this is in theory, of course, since I don't know of anyone who has
tried this yet for garden fish ponds. This is why it is an experiment. I
recently (2 months ago)added a refugium to my marine aquarium (which has
macroalgae, live sand, and losts of snails and copopods in it) and added an
additional two inches of live sand to the main tank (for a total of five
inches). The water in my reef tank has remained nitrate-free ever since. The
trick is going to be how to evenly distribute the oxygenated water over the sand
without causing it to become suspended in the water and pile up somewhere. I'm
working on a model for that right now.

George wrote:
I might experiment with a possible nitrate solution this year. If you're a
marine aquarium buff, and I am, then you know that everyone is moving
completely
away from artificial filtration and moving to natural filters. What this
means
is getting rid of all the foam, bioballs, and most any other filter media
that
convert ammonia and nitrites to nitrates. What is substituted for these are
a
refugium (garden pond people are already doing this with veggie filters),
live
rock, and thick sea sand on the bottom with a current flowing over it. The
idea
of using the sand substrate for filtration (without using the terrible
undergravel filters that suck up all the gunk in the tank and then let it
decompose on the bottom, adding to the nitrate problem) is that sea sand acts
as
a nitrate filter, because the water flow through it is very slow compared to
other filters. With a current flowing over top of the sand (as you wold have
in
a natural stream), a slow current is induced in the sand. So it allows for
the
growth bacteria that will utilize the nitrates. These bacteria also grow in
the
live rock. I know that everyone is against placing rock or any substrate in
the
bottom of their ponds for various reasons. What I plan to do is to change
the
setup on my main filter by pulling it completely out of the pond (the filter
material is all from porous rock). This will allow more room for the fish to
move around in. It will also allow me to build a fresh water reef on top of
an
8 inch coarse, dark sand base. The final modification will be to divert some
of
the outflow from the primary filter to allow it to flow slowly over the sand
base and more strongly across the reef structure (this might involve getting
a
bigger pump, or a second pump). It works very well for sal****er tanks, so
I'm
strongly considering trying this method.