Fredrick - The Nitrite levels are not raising as fast now. The last water change was probably over a week ago and today the level was .25mg/l.

There is nothing rotting in there. It's an ornamental pond with no plants. Just water, a pump and air stones.

I have notice though that the Titan 2000 pump collects solids underneath rather then send them all to the filter so I have got in the habit of sticking my pondovac under the pump weekly to get rid of any waste that is hanging around.

Otter - The strips were new. The problem is the scale. They don't read the low levels we wish to test. There needs to be 10mg/l before they start to show any colour change.

That's 10 not 0.1.

Whats the Nitrite like now?

Sorry for the late reply.

The pond sprung a leak and was being constantly topped up with water.

The leak is now fixed and the Nitrite and Nitrate are a little high. I have stopped feeding now for winter and will monitor the water quality as we go.

Should I give the pond another dose of a filter start bacteria or wait 'till spring? I'm thinking that bacteria may die off over winter anyway, but would like your thoughts.