I ditto tiller and others. Good advice from all so far. The only thing I would add about chemicals...is that there is one bottle of stuff you really should have, and that is a water treatment for Chlorine and Chlorimines. Chlorine is not that bad if you add less than 10-20% of your total amount at once. The fish can get Gill Burn if they play in the hose spray so put the hose in a area they can't get to. The chlorine will hurt your bacteria colonies in your bio filter but won't wipe em out. After a day or two contact with the air will dissipate the chlorine (it will go faster if you have an airator or waterfall). Chlorimines though are baaaad. They will never leave your pond without being treated with an additive. You can call your water company and see if they use chlorimines. If they do, then you need to get in the habit of using a neutralizer every water change. If they don't then you can get away without, unless you notice your plants being hurt by chlorine when you change the water. "Bad stuff" on the bottom are organic compounds like leaves, fish poop, dead fish etc. As it decomposes it will create a layer of mud called "muck". It's black and smells bad. If your pond ever has a sewer odor that's a sure sign that your muck has run amok and the fish are in danger. When this happens oxygen levels drop and you start getting brown algae and your water will look like rootbeer. Anaerobic bacteria start to go to work in the oxygen free environment. This is a fish death sentence. You should regularly scoop out the majority of the muck leaving as little as possible on the bottom after it settles back down. "Regularly" depends on your pond. More trees, dust, pollen, weaker filter etc mean you need to clean it up more or less than others. There is no rule about how often to clean. To clean out muck, you just need to scoop it out. You can do that by hand, with a bucket or shop vac. One thing I like is this little attachment that goes on the end of a garden hose. The flow of the hose water creates venturi suction that pushes the muck into a little nylon bag. Keep in mind that with any of these options you will stir up the muck and it will take a day or so to see improvement. If you do it regularly, the stirred up muck isn't a problem for the fish. But if you have a deep layer of it you might want to do what destany said above, and move the fish into a container for a bit (filled with pond water!) as all those bad compounds will be spiked during the clean. If your depth is closer to 3 feet I would still think about either getting rid of the goldfish (donate them to a pet store or other ponder) or the koi. With either 3 koi or 11 goldfish you have about the right fishload. But with both, you have about double what you will need in a year or so when they get big. If you are dead set on keeping all of them, you need to plan on losing some to stress or plan on getting a heavy duty biofilter and/or doing regular muck sweeping.

Thank you all for the input - sounds like FILTRATION is indeed where I need to go with this. Actually I only have 4 large sarassas & 2 medium sized shubunkins in the pond right now Big Red (large red comet) and 3 small comets are still in the basement tank after the disaster I had earlier in the spring. I wasnt testing the water (didn�t need to before, I had many easy, trouble free years with 4-5 fish in a 150 gal pond) and when I finally did I did there were nitrates, nitrites AND some ammonia, which necessitated the first of several big emergency water changes . I had a lot of debris powdery brown stuff from the pine tree falling into the pond throughout April & 1/2 of May which I was told was pollen. The water turned into dark brown muck not clear tea colored water, but dark particles that couldnt be seen through Honestly, I would not want more fish than the 10. They are large enough that the pond doesnt look empty or sparse at all. I meant I would give away fish if I was to decide to reduce the size of the pond. Mike -thanks I think I may be taking a little road trip!! Well I guess Im learning - the whole mess earlier this spring was a wake up call - either take care of the fish properly. Or not, and pay the price. When I started, I thought oh well just replace the fish each spring. But when you have them as pets for 10 or 12 years it kinda changes your outlook. Besides, a few healthy active fish are much more pleasant to look at than a lot of them that are not doing well or lethargic because they are too crowded. Hmmm trickle tower - that could work. My original concept was more like a trickling, gurgling bubbling spring coming out of rocks �-rather than a sheet of water coming over a ledge like a waterfall. Or maybe something like a stack of plastic stacker trays with rocks in them inside a tall bin?

It is possible to install the skimmer inside the liner but not desirable. As Jeff stated,one problem is that they will float. This is especially true if you have filter pads above the pump area. I tried this once and even put solid landscape blocks in the bottom and it still floated. Another problem with in pond skimmer is that some of the floating debris will collect around and behind the skimmer box. As Jeff mentioned you should be using PVC and it is designed to be buried in the ground. They make a flexible PVC that works fine and I use it for all my pond plumbing which uses 1 1/2" or smaller pipes. If you decide to use that and have to use any fittings I advise you to use electrical PVC fittings instead of the normal white fittings. Properly glued PVC fittings will withstand the normal shifting caused by freezing and thawing. One thing that I'm not clear about is what you have in the pond. Is it a water garden with just plants or do you have fish as well? With respect to circulation at the bottom of the pond, if you want to do this to keep the bottom clean you may be successful but the result will be cloudy water. Skimmers are not designed to handle the stuff that sinks to the bottom of the pond (fish poo decaying plant material and mulm) they are designed to collect the stuff that floats. You should have some other kind of filtration to deal with the sinking stuff. When the bottom stuff gets pulled into the skimmer and goes through the pump it gets ground up to finer and finer particles and if you don't have a filter to remove it the it just circulates around your pond and the water gets more and more cloudy. Does your waterfall have any kind of filter? Hope this helps.

Let me say that "chore" is an understatement . . . I've got a 850 gal pond (9' x 11', 3' deep) that I spent 3 days cleaning and re-setting to fix a multitude of problems (excess debris, excess rocks/gravel, overgrown plants, loose rocks, etc), but then again, it was just me and I took the pond all the way down to the liner. When I cleaned out my pond, I setup an inflatable kiddie pool in my basement (8' diameter) with an aquarium air bubbler, and used an external water pump to pump water out of the pond and into the pool (I put it in the basement because then I didn't have to worry about a predator tearing a hole in the pool). I then moved my potted plants into the pool, and then proceeded to drain the pond using a sump pump and discharge hose into the back yard. I used the sump pump because I had it available, and having the float valve made it easy to turn it on or off, in case a fish got too close to the intake. Smallish debris also didn't phase it so I didn't have to worry about the pump or hose getting clogged. Once most of the water was pumped out (and there was no place for the fish to hide), it was time to get the fish out of the pond and into their temporary living quarters. The lowered water level made this much easier, and I used some 5-gal buckets to move them from place to place. After that, I dug a hole in the debris in the bottom larger than the pump, put the pump in this hole, and then proceeded to drain out every last ounce of water that I could easily get - this also allowed me to see if I missed any fish in the initial catch. I also had a hose with me so that I could hose down the sides and get some of the smaller, floating muck taken care of by the pump discharge. At this point, you'll be standing in a big, muck-filled hole in the ground. Congratulations! Now the real work begins. Any overgrown plants that could be easily reached were dealt with first. If I wanted to save them then I took them out and stuck them in the pool. Any that I didn't care about got thrown onto the compost pile. I used a plastic scoop (3-quart horse-feed scoop from a farm supply store - flat bottom, rounded sides, integrated handle, plastic so that I wouldn't damage the liner) to scoop out the muck and debris and dumped it in a pile outside of the pond - wheelbarrow or garden cart would be good if you just want to dump it into the compost. Periodically I would hose down the pond walls to clean off any extra gunk and then pump it back out with the sump pump - this made it easier to see/work with since scooping out the muck caused any remaining water to turn into an impenetrable black morass that made it impossible to see what you were doing. Once as much of the debris is removed as possible, I then hosed everything down one last time and pumped it back out as a final "rinse". The above took me a full day to do. Now you need to put everything back together: replace any rockwork that was taken out, re-fill the pond and treat the water for chlorine (if necessary. This was day 2 for me), let it circulate for a couple hours or a day to get the last remaining debris/chemicals to dissipate/filter/settle out (there won't be much - I had probably 2 cups worth when all was said and done, and I didn't worry about it), replace/re-pot the plants, and then finally move the fish into their newly-cleaned home (day 3). be sure to treat them as brand new arrivals, getting them used to the new water temp and parameters first. When I cleaned out the pond, I had cleaned only the pond - I didn't touch the filter at all. Only when the pond had been up and running for a week did I cleanout the filter. For an overpopulated pond like mine (50+ goldfish. I inherited the pond and fish from the previous occupants of my house), the water parameters stayed at 0 afterwards, and the cleanout didn't cause an algae bloom, either, but I can't guarantee that your pond will react the same. It was also the first time I did anything like this, so it's quite possible the above is not the most expedient/efficient way to do this. Good luck with everything (sorry the response is so long)! - Mike