The water fall is acting as a skimmer for the top pond and all the dust,
dirt, debris that lands on the pond, plus any floating plant material all go
over the water fall to the small pond at the bottom. The pump will
recirculate some of this stuff, since it will be dispersed through the water
column. The bottom pond will fill with muck, mulm, fairly quickly and needs
to be cleaned regularly. When I started out, I had a similar setup to
yours, and then added a 1500 gallon liner pond to the mix, and then the
amount of mulm built up very quickly in the bottom pond.

You really need a solids handling pump that you can put on the bottom of the
small lower pond and then have the water circulated through some form of
filter that can be easily cleaned, or you will be cleaning the bottom pond
very often, or you will be building pockets of hydrogen sulfide gas that
will kill fish, if you want to have fish in the lower pond. If you don't
mind not having fish in the lower pond, then it can be a settling tank,
setting the pump intake near the surface, and as material builds up, turn
off the pump, use a shop vac or similar to clean the pond and then refill
the bottom pond and restart the system.
--
RichToyBox
http://www.geocities.com/richtoybox/index.html

"jammer" wrote in message
...

Here is what has changed:

I added about a 150 gallon raised preform that runs into the bottom
pond. I built a little waterfall to run into the new top pond and
dropped a 250gph pump into the bottom pond. This is when i notice
large dirt particles being circulated around. ('ll be cleaning it soon
but still...) I know i need a filter but what is the easiest/cheapest
way to go for my small set-up? A rubber maid tub with some sort of
material...... I can do a web search but what can i use that is fish
safe? I itch just thinking about insulation, anything easier to
handle/clean? And why are my fish ok in the top pond but not the
bottom?