Rain Water from garage roof

hi guys
i have a question which i have asked our local aquatics places on and have had many mixed replys can you help pls
We have a gutter on our garage and the downspout runs next to our raised pond. would it be safe to divert the downspout into the pond or will this harm the fish???
the garage has been built 2 n half years the pond has been established 2 n half years also. we have a mixture of koi orfe shubunkins goldies and sturgeon
all advise welcomed thanks xxxx

What do you have for roofing material on the garage? No matter what material I don't think it wise to use for the pond. You are bound to get some type of runoff that could change the water parameters of the pond.

Most roofing has petroleum products in them. I think the water could be toxic to fish.

thanks for the advice its slate tiles on the roof and mortar to secure so we will give that one a miss

I'm thinking of doing the same. I would think a metal, wood, or slate roof would be fine but, I'm really not sure. I have a very large pond that can not be filled with just a garden hose and need some sort of water source for the late summers. When I put my piping in I plan to have a ball valve to divert it away from the pond when not needed.