On Wed, 07 Apr 2004 00:13:14 +0100, Cardman
wrote:

On Tue, 06 Apr 2004 09:49:36 GMT, "Michi Henning"
wrote:

The canister is rumoured to contribute to nitrate
removal. Apparently, sintered glass contains enough small
pores for some anearobic bacteria to break down nitrates.

I will have to look into that then.

And that I did.

So anaerobic bacteria can be used to create a further step in this
cycle, which will convert Nitrates input to Nitrogen output.

Very nice, but I doubt that a general slow filter is good enough, for
reasons that I will soon explain.

As anaerobic of course means without oxygen, which is why you will
only get these bacteria living where there is no oxygen. And the
common way of doing that is to have other bacteria using up all the
oxygen first.

And that oxygen using bacteria is of course the same one that turns
Nitrites into Nitrates and even this fish poo into Nitrites.

So in order to get your anaerobic bacteria you need a very slow filter
that has time to use up all the oxygen. And the simplest way to do
that is just to use a long (like 20 foot) narrow (like 1/4") flexible
pvc tube with a flow control on one end. Not of course to forget a low
pressure pump in order to get it in there in the first place.

Make sure that the flow is slow enough (1 to 4 gallons an hour is
recommended) by using a simple flow controller (found in most DIY
stores) and some of the tube would contain your oxygen eating
bacteria, while the rest of the tube would contain your anaerobic
bacteria.

From this information we can see that the longer your tube is the
faster the flow rate can be, where no Nitrate reducing results means
to slow down the flow rate or to use a longer tube.

People who have already made their own de-nitrator filter using a 17
and 20 foot tube have reported that 3 mg/l of Nitrates can be turned
into Nitrogen each and every hour.

Or as I just read one person used a 75 foot long tube and recorded a
Nitrate level on the output end of 5ppm less than the normal aquarium
level. Although at just 2 gallons an hour I expect that he should
increase his flow rate.

The only thing to watch out for this that this anaerobic bacteria will
also turn Nitrates back into Nitrites, which means that the output of
this tube should ideally be fed into the input of another filter. So
that these Nitrites can be converted back once more to Nitrates.

So even at my 100 ppm level of Nitrates, then this can be reduced to
very low levels in under 2 days. Naturally, it will take weeks for
your bacteria to just started fully in your tube, but that is one good
method for removing lots of Nitrates.

Kind of good if you want to have lots of fish in your tank, where the
only problem is keeping Nitrate levels high enough for the plants. And
well this de-nitrator tube won't quite remove all of it, when the
water moves so slowly.

Since I plan to use a high speed external cannister type filter on my
larger aquarium at least, then I could attach such a device with the
input as a branch off the output of this external filter. And then the
output from this tube can be linked into the input of this external
filter.

So something that I could certainly get around to, when this would do
a much better Nitrate reduction job than what many plants would.

I am just wondering who sells an already assembled kit with
instructions, when that saves the pain of if you get some aspect
wrong.

Cardman
http://www.cardman.com
http://www.cardman.co.uk