Can I just second the “don’t get too many plants”.
I’ve had my pond three years now and have pulled most of the plants out. I’m no expert so won’t comment on specifics but so many spread it was ridiculous. One that was a kind of mint was a particular sod. The ‘reed’ type thing pictured was tiny when I bought it, and it’s still in its basket, but it spreading like a bugger – I’m leaving it though as the frogs love hiding in it, but an example of how something initially about 5″ wide and a few fronds can spread.
Forgive the liner/general appearance – I’ve done some remedial levelling and clearing of wild flowers around the pond, which were a bloody terrible idea in hindsight – I’ve realised wildlife/wildflower areas are for those with fields or huge gardens they can allow to neglect.