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Hello All,
my problem is the high NO3 in my tank, actually 25 to 30 mg/l, and I see no
chance in the moment, to reduce it. The reason for high NO3 is probably to
many fishes, and I will not kill some of them. A thumb rule say, 1cm fish
for 2 liter water, my ratio ist about 1 cm fish for 1.1 liter water. I will
try to reduce NO3 by
1.) special type of biologic filter, so called "slow throughput filters"
(stf), or (and)
2.) a plant filter.
To 1.)
Stf are distinguished, in opposite to "high throughput filters"(htf), by an
extrem low water flow and a big volume. The low water flow through the
filter causes a defizit of oxygen in it and therefor the process of
denitrification will start, if the oxygen is low enough. My tank has a
capacity of 200 liters. Has somebody experience with construction of stf
(volume in ratio to tankvolume, rate of flow, material inside the filter,
type of low flow pump a.s.o.) and of course praxis experience? In any case I
would run my htf in the first time parallel to the ltf.
To 2.)
Alternativ or in addition I will establish a plant filter. One year ago, I
did already so, and I measured NO3 and made a diagram. I got a reduction of
NO3 some weeks after starting the filter and an increase of NO3 again some
weeks after removing the plant filter. As plant I used the airrootes of
philodendron. As far so good. My concern is, that the plantroots will not
only "eat" NO3, but also the furtilizer, I put into the water, and which is
foreseen for the Tankplants. Do you have concrete knowledge about this
effect? Is it necessary in this case, to increase the amount of furtilizer,
getting shure, the waterplants have enough?

I would be happy to get some information to points 1.) and 2.) and I thank
you very much.
Bye bye, Klaus Haber, Ingolstadt, Germany.