What to do in the event of rain?

[missyme06]

When it rains , I mostly let it rain. You , and neighbors are the biggest danger, that is herbcide, insecticide, etc used in the yard. If you ignore the part in the book , like I did , and build it where runoff can get in. Floating plants overflow out but the fish seem to go down during rain ; I have had a few swordtails go exploring a few hours after thr rain ends and get out.

we just put decorative rock around the top edge of my pond with about a 1/2 inch between each rock. when every it over flows the water runnes between the rocks and nothing gets out.

 

[blacksmith37]

Although rain can be very acidic due to CO2, NO3 (from lightening) , and SO2/3; it is VERY dilute, so it is no problem in pond or aquarium ( been collecting rainwater for decades ).
An analogy I like is electricity. A static spark ( like 1 inch long in Denver winter) is up to 30,000 volts but "no" ampereage, so no problem. The pH is like the voltage and the equivalents or concentration is like the ampereage. It dosn't matter what the pH is when the concentration is very dilute.

 

[Muske]

If you use a skimmer box, which is awesome because you can house your pump in their and collect wind blow debris in a collection basket. You will probally have enough room at the top to drill a hole for any overflow. You can then dig a trench a few feet away from the pond, (more is better). Attach a hose that will then lead to a dry-well of gravel. This can be built and buried completely out of sight. It will handle a lot of rain, all though in the event of a huge rain, say four plus inches, it might not be able to. I've never had any fish go awol, but mine are pretty large goldfish and their is a lot of boulders around the edge which I think that can't get by.