Stagnant mini pond- help needed!

[Tringa]

In my limited experience of cleaning and refilling a pond the frogs and newts are unbothered by tapwater.

You mentioned yellow flag. Can understand why you want one - a good native plant but very large and I think too big for you pond. The one we had in our pond go so large, a big spread and about 5 feet high, we had to give it someone with a larger pond.

Dave