Question
We just had a pond built and the runoff from the roof, 3tab roofing, and curtain drain run into the pond.  Everything seemed fine until today when I noticed the water is foamy and I see no frogs or goldfish.  It has rained recently and I am worried the roof is toxic to the pond.

Answer
Your feeling is good.  You need to run the drain spouts into tubing past the pond to a lower level.  You don't want rain water from the roof in the pond.  First, if the roof is new, yes, it could be leaching toxins.  New roof tiles are impregnanted with chemicals including ones that can be toxic to fish. Some of those chemicals can cause foaming.  If the roof is at least a few years old, that impact is not very great unless you get a deluge after a drought when all sorts of things have accumulated on the roof (and the sun has chemically acted on the shingles).  Regardless of the roof toxicity, there is also the concern of the rain itself.  Rain is extremely low in dissolved oxygen.  It also can be acidic.  Rain has no hardness or alkalinity (it's super soft).  So, if there's a heavy rain, you will often find fish gasping at the surface from the low oxygen.  If you add even more rain water via the roof, that makes things worse.  Plus, if the rain is acidic, enough of it can lower the pH to dangerous levels (below pH 6.0).  And, the rain lowers the hardness and alkalinity which results in more pH fluctuations and other problems.  Rain rushing off a roof and into the pond will also pick up other things on the way.  Even regular rain can wash things into the pond like mulch and chemicals (avoid all pesticides and herbicides uphill from the pond).  So, it's best to forgo the bonus of topping off the pond with roof rain water by routing the drain spouts away from the pond.  We did that with the spout that flooded the area above my pond.  We ran tubing out beyond the pond which has worked for us. It wasn't too hard to do.  Good luck!

Robyn
fishpondinfo.com