I have found fishdoc.co.uk which also gives some advice.
The readings today were the first taken from the pond, and considering there is no character change in the fish or a change in pod appearance, I would assume that the readings are typical of the pond rather than a "spike".
The pond has been up and running for 12 months and all the fish have survived and are growing well. I did a full water change in the spring time and added pond-start (to deal with tap water) and bio-start bacteria when the pond was re-filled.
I have added a second bio-start bacteria sachet in the past month and I change about 5% - 10% of the water each week (I lift the filter media partially out of the filter box and use the box drain to remove sediment). The main filter media is Matala which is never cleaned - the agitation from lifting them removes a fair amount of sediment).
AN additional foam filter I installed in the box IS cleaned regularly as I consider this to be a trap for sediment in suspension.
A pond vacuum is now used monthly to sweep the crap off the bottom.
Judging by your comments and those on fishdoc, it may well be that over feeding is probable. There is plenty of green weed on the pond walls to ensure the fish don't starve. They have never been voracious feeders.
Other additives to the pond in the last 2 months are: A flocculant to help remove "green" suspended sediment. Not particularly effective. Temporary Fine physical filtration cleared most of this out.
In addition, I have used 2 courses of blanket weed control. FIrstly Interpet pond balance, which made the water milky for 5 or 6 days each dose. The last 8 weeks I have used Nishikoi "goodbye blanket weed" which was more effective and water clarity was maintained. SO there has been plenty of dying weed recently.
I have a couple of lillies in the pond and will make a special point of clearing out any "bad" leaves and old flowers which will reduce the amount of rotting vegetation.
Food until this week has been Kusuri FPF, which the fish seemed to enjoy. I now have Nobori, however I will refrain from feeding for a few days and see how the readings change.
Posted on Aug 12, 2006, 11:45 PM from IP address 88.109.51.105