I have to admit I am bewildered. I read the MSDS from the company and the biggest difference I see from what I usually buy is it is made from bituminous coal rather than some sort of woody material. That should not be a serious difference.

I try to get the largest chunks I can find but there is usually a lot of 'dust' since it is pretty fragile. I don't really worry about that since the dust works very fast and then gets hung up in the quilt batting I use in the Skippy. In fact I often break up the chunks after a couple of months to expose more fresh surface area and that produces more 'dust' that gets the same results. I have to admit the chunks are getting harder to find while the granules seem to be everywhere.

Is it possible the batch you got has a high volume of 'dust' or powder? It could be possible that rough handling of the container caused it to break up more than is normal or it might have been the very end of a batch. You might want to contact the manufacturer and question the condition of the product. Most of the granulated product I see is pretty low on 'dust'.

If you do decide to try it, start with a small quantity to see what happens. If it is mostly 'dust', you will see a very quick reaction and the material that escapes the mesh bag will get into the filter material pretty fast. That is OK for batting but might be a problem with other filter material.

Maybe someone else here has some info.

Thanks for going to so much trouble to help. I knew the product was from bituminous coal and had read somewhere that that was desirable. I called the manufacturer, who said he'd never heard about this problem before and promised to look into it and call me back. So far, he hasn't, so I tried soaking the AC in water overnight and rinsing. After doing that twice, the rinse water was pretty clear, so I've put it in the pond. The pond water seems clearer but still somewhat tea colored. I'm wondering how much of that is due to having brownish pebbles and rocks at the bottom? And now my husband is concerned that the charcoal will rid the pond of beneficial bacteria. Is that possible?

That wouldn't be a problem with AC. First the charcoal is not harmful to bacteria or anything else that is alive in the water. In fact bacteria will sometimes use the surface of the AC as a colonizing location as it does any surface in the pond. The AC does not release toxins into the water. It does not affect algae or particulates. It functions by attracting and trapping gas molecules on it's surface in a chemical reaction called adsorption. Once it has been completely covered by those molecules it stops working and must be refreshed or replaced.

You should figure out where the discoloration in the water is coming from. Stains, discoloration and odors come from the breakdown of organic materials and the release of tannic acid or tannin into the water. Sources can be mulm, fish poo, excess food, dead plant material especially oak leaves and acorns and peat moss among other things. Pebbles on the bottom trap these and make the problem worse as the debris rots. Potting soil is a prime culprit. Do not use standard potting soil for pond plants.

Free floating debris in the water is a particulate. It can also produce brown water. It is controlled through an efficient mechanical filtration system.It can be any of the things that cause stains in the water or other things entirely.

AC does not control particulates. Mechanical filtration does not control stains and odors. All the AC you could add would not clear the water if you have material in the water that is actively rotting.

To determine if you have stains, particulates or both fill a glass container with pond water and allow it to sit undisturbed for a couple of hours. Stain will remain diffused throughout the water, particulates will float or sink.