Q.How would using my koi pond water affect the fertilization schedule this spring?
I have mugo and scott pine along with larch, juniper and boxwood.
Would fertilizing and watering with pond water be too much or would pond water be sufficient on its own?

Certified GKH Gardening Expert
I can't say with certainty whether your koi pond water would interfere with your fertilizing. This is a question for your local extension service. You may want to take a sample of the water in for testing when you ask this question.
Here's an article about cleaning koi
ponds that may be helpful:
https://www.gardeningknowhow.com/ornamental/water-plants/wgen/cleaning-garden-ponds.htm