... Is this a common occurance? Will it heal itself over time? Or do I need to do something about it? Eric
Eric,
Yes, it happens in every pond. It is the result of detritus and decomposing organic matter that has no where else to go. Fortunately it takes many, many years but left completely unchecked, ponds tend toward naturally filling in.
It takes a long period of time, however. Very long, normally.
A lot of people drain their ponds and clean out the muck. I've done that myself in one very old pond which had evolved to about 1 foot depth of water and the rest muck....several feet of it.
There are a couple of things which can delay and possibly even reverse this natural occurence...aeration and Tilapia.
You probably aren't surprised by aeration....but maybe have doubts about Tilapia. Check it out. Tilapia eat detritus and decomposing organic matter. They litterally clean the bottom of the pond. There is an article online, forget the exact link, that describes a huge Tilapia stocking program on the Nile/Aswain dam. They had a severe problem with muck buildup and stocked large numbers of Tilapia to remove it. I forget the exact numbers but they measured the decrease in depth of the muck every year due to Tialpia and it was significant.
In ponds that have both aeration and Tilapia, I do not experience muck build-up. In new ponds, Tilapia alone seem to be able to keep it in check....older ponds with significant build-up experience improvement, but it is very slow.