"Michi Henning" wrote in message
...

Well, you could try lots of plants, and slow filter. That will contribute
toward reducing nitrates. You also add a denitrification filter. From
what I hear, they are a bit finicky though -- the the flow rate too high
and they do nothing, and get it too low, and they put hydrogen sulfate
into the water. (H2S is toxic.) But such a filter may not be a bad choice
given that you have high nitrate levels in your tap water.

I've had very little success with denitrification filters. About 10 years
ago I tried a
sera denitrator and that failed dismally - although that may have been
because I didn't
understand the process and my flow rate was probably too high.

Recently I tried a home brew filter using around 50 metres of tubing, but I
couldn't get
the flow rate correct to maintain an anaerobic culture. It just clogged up.

Best bet to reduce nitrate levels are lots of adequately fertilised plants
and water changes.

Even that has it's challenges :-)



Graham.