Microbe-Lift/Sludge Away
Question:
Microbe-Lift Sludge Away is safe for Koi and Goldfish if used as directed.
It is used in our display ponds on a regular basis.
Answer:
Testing the pH to see if the rain significantly changed it is a good idea.
It is possible though that the pond gets just enough run off from the sides to add nutrients that feed algae.
Keeping plenty of beneficial bacteria in the pond and dosing it with a flocculant like Sheer Clear or Accu Clear right after the rain should alleviate the problem.