UPDATE - The First Year
Well, it has been a year since we installed our pond. This is an update on what we have learned about water gardening.
The first fall.
The first winter
I had the same problem with the main pump. The fine-mesh pre-filter material that goes over the pump inlet was constantly getting clogged do I finally just removed it. Later, I learned a neat trick. Put the pump in a large plant basket along with some medium sized gravel. Discard the original pre-filter mesh and cover the basket with a piece of coarse mesh. This keeps out the larger debris but passes the smaller debris on to the main filter for removal. This arrangement requires much less frequent cleaning.
I finally bought a UV filter which passes the water from the pump past an ultra-violet light and kills the algae. I have had the UV filter in use for about a week and I can already see a considerable difference in the clarity of the water. It is not crystal clear yet, but I think it will be in a few more days.
UV filters are fairly expensive (around $125) and many experts say they are not necessary if you have a proper eco balance, but I could not get the water clear this year.
Update 2004 - The Leak
We developed a leak in the pond. I noticed the water level dropping and frequently had to refill the pond. I have never had a problem just adding some water from the garden hose in small amounts. I have read that you can replace 10-20% of the water at a time without harming the fish. However, we let it go too long and had to add a lot of water. I guess the chlorine in our city tap water was too much for the fish and about 12 of them died.
I knew I had to drain the pond to find and fix the leak. I bought a cheap plastic kiddie pool at Wal-Mart and filled it with pond water. I then used a net to transfer the fish to the kiddie pool. I pumped the water out of the pond and found that there was a large split in the liner right below the pump at the deepest part of the pond.
Rather than try to patch it, I decided to buy a new liner. I went to a local pond supply store and bought considerably heavier lining material than I had previously used. It was pretty expensive but I didn't want to do this again for a long time. I added some extra padding under the main pump. I don't know if the split in the lining was caused by vibrations from the pump or if it was simply where the most water pressure was on the lining, or both.
We refilled the pond and let the water stabilize for about 3 days. We put the fish back in and everything was fine. I did notice the water became green and murky again pretty quickly. After reading about this problem on the Internet, I ordered an ultraviolet light to pass the water through. This is supposed to kill the microscopic bacteria that makes the water green. After a year of use, it made no difference.
Update 2007 - Bad Winter
For the last couple of years, I let the waterfall pump and the small fountain pump run all winter. The fountain kept a small area unfrozen even when the rest of the pond was frozen over. Even thought the waterfall often had ice on it, the water continued to run behind the ice.
This year, we had a really cold stretch of about 2-3 weeks below freezing and the waterfall pump (or at least the hoses from it) froze. I disconnected the electricity and figured whatever damage was already done so I would wait until things thawed out and hope that it still worked.
Well, when warmer weather finally came around I found that the waterfall pump was OK but the freezing water had slit open the top of my $300 in-ground filter and broken the glass in my ultraviolet light filter. I bought a new in-ground filter and UV light.
When I asked about the light and said that my old one never really kept the water clear I learned that I not only had too small of a light for my 1000 gallon pond but I was also running the water through it too fast. The water was going past the light so fast that it didn't have time to kill the bacteria. When installed the new light, I also installed a ball valve and a "T" in the plumbing so I could slow down the flow of water through the light filter (also called a sterilizer). I'll let you know how it works.
The fish are doing well. I estimate we have around 30 goldfish, fantails, shubunkins, and comets. Some of the comets and fantails have grown to about 10 or 12 inches.