Yeah, it is probably from iron in the water. I wonder if you might be able to fill it with water, put in LOTS of Clorox and let it soak. (Certainly keep it from where the birds can get to it while it is soaking!). Wonder if that would take it out?

Then, if that does not work, I wonder if ZUD and a good scrubbing would get it out. IT's like Comet cleanser for the tub...heck, maybe even Comet or Ajax would do it. I wonder if the concrete would absorb then? You'd have to rinse well for sure....

Assuming you get them out, I would then go to the Home Depot store and find a sealer for the concrete, assuming it IS concrete, apply, dry and refill.

Robin

I have, or used to have since it rusted clean thru, a birdbath that is made out of some sort of metal. I was told that the iron it would create once adding water, would not hurt the birds at all. I would think that clorox or anything of that nature, would get into the "pores" of the cement and would cause harm to your feathered friends. I wouldn't worry about it.

Terry

Update - I tried scrubbing it with a hard brush, and a slimy film came off (mold maybe?). Then I let it dry out completely in the hot sun before filling it again with water. I couldn't get the rust stains completely off, and there's still some black stains that look like they might be some kind of mineral stain, but hopefully it's pretty clean now for the birds. Thanks for all the feedback.

I also scrubbed it with antibacterial dish soap and rinsed it out. I hope that was okay/safe for the birds.

My guess is if you can't even scrub it off with a hard brush and water, then it's probably not going to come off with water alone and therefore is not going to cause a problem for your birds.
As for the clorox comment, with all due respect, it's not going to "get into the pores of the cement" and cause harm to your birds. Bleach is just a source of available chlorine, which if rinsed adequately will not be in high enough concentrations to harm anything, not even the bacteria or mold you killed in the first place. Plus, much like tapwater that is allowed to sit, a dilute bleach solution will lose most of it's effectiveness in a short period of time, especially under the high organic loads that would be present in a birdbath. Come to think of it, the residual chlorine concentration that is left over is probably not even as high as what is already in the average municipal water supply. And if you're filling up the birdbath with the hose...well you get my point.
So, by all means, wash it, scrub it, bleach it, rinse it, but just don't worry about it.

We have a birdbath that seems to be in good use made of some kind of clay or molded plaster. It collects scum within a few days. DH uses a brush to scrub it once a week and water is changed or added at least twice a week. Do you think a drop or two of bleach would help keep it clean, yet not hurt the birds?
When my daughter purchased it for us they sold her some type of drip system too add on to keep the water from getting stagnant,but that's not a big problem and we don't like the water constantly dripping. We add water when ever the hose is on and the sprinklers hit it every other day.
It is located in the middle of some mondo grass under three birch trees.
Thanks!

Please don't use a clear concrete sealer on a bird bath. Concrete sealer has to be reapplied to concrete (ie, patios, driveways etc...) because it does leach off after time. If the sealer is leaching off into water, I don't think you want the birds to drink at it. An acrylic/epoxy paint made for concrete can be applied during the winter when your birdbath has to be closed up anyways and then will be safe for holding water and the birds to drink from. Then when you clean it, use a soft bristle brush so that you don't scratch it up and your birdbath will stay cleaner longer. I wish the companies that mold bird baths would just apply the bird-safe paint before they send them to the stores/distributers and there wouldn't be any problems.

I have two small birdbaths and I empty and spray them out every other day but I don't really worry about the algae that grows in them. Birds will drink and bathe in a mud puddle after all. As long as your water is fresh and not breeding mosquitoes, I would think the birds will be happy with it.

Drippers are a great gift! I'll take it if you don't want it ;o) They just recycle the water, they don't continuously add new and the sound of running water attracts birds like crazy. I water as per our city water restrictions every other day and the minute I turn the hose on, birds come from far and wide. I can count the seconds until the hummers show up when the water starts hitting the leaves and the jays are extremely attracted to the sound of water. Try out your dripper and see... I wish someone gave ME one for a gift ;o) :oP

Barb
southern Ontario, CANADA

I read an article about this rust staining on concrete birdbaths. I think it was DIY website (from the tv channel). It said to put a small piece of copper piping in the water, or a few copper pennies (minted before 1982, when they were pure copper). My hubby found a small piece of copper pipe and we tried it today, after I scrubbed the bath clean with an old green kitchen scrubby. I'm anxious to see the results, and I'll let you know. I've tried to clean my birdbath every week but the rust is really getting bad.

Today I used regular baking soda and a good scrub brush and the black mold came off pretty good. There is a very light shadow where the black was. I think the birds will drink from there now, they wouldn't touch it before.

If you bring the birdbath in for the winter you can try bleaching it then, it won't hurt. A good rinsing afterwards and exposure to the sun when you put it back out will take care of any residual chlorine. Anyone who owns a pool can tell you that sunlight burns it out of water quickly.

I scrubbed the spots with an old kitchen scrub brush. Spots came right off. Baking soda sounds like a great idea though- thanks!!