IS moldy hay safe to put in pond to clear water?

There are several good reasons to put some straw in a pond - it's supposed to clear the water if it's muddy/new, help build a biofilm to make it more leak-proof, and feed tiny critters that will keep algae at bay. But around here straw costs MORE than hay, and I've got a few bales of hay that got wet and moldy and aren't fit for my livestock any more. Can I safely throw it in the pond? Or will the toxins from the mold contaminate the water?

It's a new pond, practically dead since it's been in the ground through winter only and nothing has had a chance to colonize it yet. I'm looking forward to bringing it to life with plants and critters this spring. My best guess is it's between a half- and quarter-acre in size.

If it is safe to use the moldy hay, any experts out there who can tell me how many bales to throw in? I'd guess only 1 or maybe 2 at most. I don't want to make it a stinky pit of fermenting rotting stuff, but I do want to start some daphnia growing there, since they're a foundational food species for fish fry and other small stuff.

I'm no expert, so I googled around a bit.

This was the best and most detailed info I found:

http://www.graystonecreations.com/how-to-control-algae.shtml

Most things I saw specified BARLEY straw, because it is a natural algae controller.

As for hay, the difference between hay and straw of course is that straw is just the stems of the plants basically, and hay includes seed heads and is generally random plants, weeds.

My concern would be that you may cause unwelcome weeds to start growing around your pond, I don't know if it would actually be " toxic " though.

I read there's nothing special about the barley that makes it kill algae. It's just a home for the one-celled organisms that feed on it and then feed daphnia and other tiny critters, which either use up the nutrients that would otherwise feed the algae, or they eat the algae, depending on what they are. You can use leaves, hay, etc. and get roughly the same results.

ask this gal , she has been doing ponds for a while, and may know

http://cowgirlscountry.blogspot.com/2007/11/raising-your-own-shrimp.html


don't look at her recipe's if your a vegetarian tho......

Renate, you might want to read through this factsheet from the UK Natural Environment Research Council.

The researchers conclude: 'Hay and green plant materials should not be used because they can release nutrients which may increase algal growth. Also they rot very rapidly and may cause deoxygenation of the water.'

The factsheet discusses the mechanism of action (it's interesting and complex, the straw degrades and lignin is released, the concentration of long-chain dissolved organic carbon increases in the water, and this interacts with sunlight to eventually create trace amounts of hydrogen peroxide which persist for a few days...an algacide which is continually 'refreshed' as the straw continues to rot).

The researchers believe barley straw to be more effective than other straws.
I wouldn't use hay.

The factsheet also talks about how much straw to add and how frequently. It's an interesting read. I think I'll try some barley straw in the spring. Please let us know how it goes if you try any experiments. cheers.