I see a pond, but not huge reservoirs of ashes in that video. Please refer to my recent thread:
Cremated remains, bone ash, and water-solubility // the ash ponds
viewtopic.php?f=2&t=12278
One cubic meter of space could fit the burnt remains of 400-500 people. At Auschwitz, it is alleged 6,000 people (or roughly 12 cubic meters worth) of people's remains were produced every single day for months at a time. This bone ash is not soluble in water and would necessarily be lining the bottom of the pond... if not filling the entire pond.
Crystal wrote:Lamprecht wrote:Crystal -- can you show these massive heaps of cremated remains that would necessarily be there?
Yes. Note the mound on the right:
Your own source says that image is the "Remains of “the little white house” at Birkenau"
Sometimes dirt can look like bone ash. This is what cremated remains look like:

Obviously, this "bone ash" is comprised of mostly calcium. In contrast, soil is generally between 1-2% calcium.

I pointed out two sources which claimed between 66,000 and 70,000 people died at Auschwitz. I calculated that this would result in 1/2 a million pounds of remains. In terms of volume, this would be 140-175 cubic meters of burnt remains
In contrast, it is typically claimed over 1.1 million people were murdered at Auschwitz. For this to be true, that would mean about 8 million pounds of burnt remains was produced, with a volume 2,200 to 2,750 cubic meters. Let's just round down to 2,000 for convenience sake.
If the nazis allegedly murdered 1.1 million and cremated these remains, that 2,000 cubic meters of remains could fit entirely on an American football field, which is 5,351 square meters. The remains, if evenly distributed on this football field, would be 37 centimeters high, or 14.6 inches... which over a foot.
So, Crystal, do you seriously believe that there exists at Auschwitz the burnt remains of over a million people, with the volume equivalent of bone ash equal to an entire football field with over 1 foot high of bone ash covering it? Please note that the 66,000-70,000 people who died, according to the sources cited above, would also have been cremated and their remains should be there although that does not suggest or imply that Auschwitz was a death camp.
I am not quite sure how this millions of pounds of remains could be magically lost in a pond. It would fill up the entire pond. There would be enormous pits full of ash, as well. which could be excavated.
Here are some images to help you understand how large an American football field is:
