Thanks for the link pansyface - I think we will give them a miss - yes oxygenating plants are useful Lyn, but as our PH is still on the high side we are disappointed to find that most of the plants die.
Try adding a bit of vinegar GD but slowly and check PH afterwards. I take it you've filled it with hard tap water. As it gets up with rainwater over the next few months things should improve. As ever, research before planting and patience afterwards.
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
Not tried the vinegar Obelixx although it was suggested previously to us last year. We have at least got the PH down from 9..... to 8.5 in the last year - the aim is to reach 7.5. Patience isn't my strongest point, but we are doing all we can to bring the reading down. There is no tap water in our pond - well and rain water only. The well water reading is 7.5, so that isn't the problem.
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