How Ponds Work
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I am no expert, and there are many different types of ponds & filtering systems, this is my simplistic view and the type I have.



Pond #1 In Houson - 150 gallons
At my house in Houston, I didn't do any research about ponds, I just bought a kit from Home Depot. It came with a black sheet of plastic, a pump, and a ceramic frog to spit the water out. I dug a hole in my front yard and put the plastic down, then lined it with rocks, filled it with water, turned the pump on and that was just about it. The spitting frog provided the aeration, but I really didn't have a filter of any kind, I just changed the water often to get rid of the waste & freshen it up a bit. Problems - I would change the water by having the frog spit onto my lawn for a while. I kept forgetting to come back out after a period, and often came out to find almost my entire pond drained. Soon I started putting the pump on a brick, so it would only drain so far and then run dry for a while. Also with changing so much water at one time, the chlorine and big temperature change would kill off a couple of fish every now and then. I stocked it with cheap feeder goldfish and bluegill (sunfish) that my kids and I caught at a local lake, so it wasn't really that big of a deal till this one fish I had for a long time died, it was pretty big. I didn't like all the pleats in the plastic, and the pond was a bit small, so I went to buy one of those pre-formed liners.



Pond #2 In Houson - 250 gallons
I bought the biggest liner they had at Home Depot and it just barely fit into my van. Putting it in place was a bit of a pain, I dug the hole but getting a hole the right size was tougher than I thought. The pond would deform to the hole it was in and I tried backfilling and compressing the dirt, but it never really looked right. So with all the fish killing in the last pond, I figured I needed some kind of filter. Thinking that a pond must be just like a pool, I attached a small plastic jar with fiber fill pillow batting to the circulation pump. The batting would turn green very quickly, and then after a couple of weeks it would get really slimey and start to clog the intake of my pump, so I would throw out that batting and put some fresh stuff in there. The water would get green after a month, and I would do a big 30% change (using my brick trick) and only a couple of fish would die.

Then one day I suddenly had pea green soup. I did a big water change, and it didn't fix it. So I scooped all the fish into a bucket, and did a 100% change. The pea green soup came back about a week later and I was frustrated. A quick call to the local pet shop and they said I needed to get a UV sterilizer, they had one for $300. Went onto ebay, bought one for about $70 and it cleared up the soup.

Since the fish were living longer, I taught them to eat cheerios from my hand. I was really getting attached to them, then suddenly most of them dissapeared ! A possom had stumbled onto our pond and the fish thought it was feeding time, swam right up to him and quickly became dinner. That thing really irked me off, so I stayed up all night and gave him a Texas case of lead poisoning.

This pond was never really clear, it was a little murkey, even with the UV sterilizer.


Move to AZ, Get Educated
We moved to AZ, and I decided that I really should know more about fish ponds before I made one here. So I started roaming around the internet looking for info, and found a TON of it. The fish pond hobby is pretty darn big with all sorts of opinions on various stuff, almost too much information. I am a simple kind of guy, I really just wanted to make the simplest and easiest pond I could that didn't take much maintenance.

Bio Filters
I am very familiar with swimming pool equipment - basically a swimming pool has screen in front of the pump to catch the big stuff like leaves, and a "mechanical" filter (a sand or DE powder filter) that removes the small particles from the water. The chlorine tablets then create a chemical envioronment to kill all of the biological stuff in the water. Those two keep it crystal clean. A pond has living stuff in it, so you can't use the chlorine, what you need is to make a filter system that is completely different from a pool. There are numerous types with various configurations, the kind I am using is called a "bio filter". Basically it is a box of rocks that the water is pushed thru, and bacteria grows on the rocks. That bacteria will eat the fish poop and algae and convert it into something that is harmless. The box or rocks needs to have water flowing over it all the time, you can't start and stop the water otherwise you will kill the bacteria, and the water will get mucky until the bacteria grows back again. This box of rocks also traps the small particles and acts like a mechanical filter, so it needs to be cleaned out. One popular way to clean them is to put a valve and drain on the bottom so you can open it at times and let the muck drain out -- but that supposedly still leaves a lot of muck in there occasionally the entire box of rocks has to be emptied and cleaned by hand. Another method is to blow air bubbles in the bottom - the muck then rises to the surface and can be directed out of the filter onto the lawn, which really likes to eat fish muck. So if you read above, the pillow batting filter I made was essentially doing that, and I would throw away the batting right when the good bacteria started growing on it.

Aeration
Fish need to breathe oxygen, so you have to put that into the water. Most ponds have a water fall, trickle tower or fountain to splash the water and add the oxygen in. There is also a thing called a venturi, which is a high pressure water line with an air tube led to it. The air gets stucked into the water line and makes a bubbly water jet. I haven't found a good website on which methods put the most oxygen into the water with the least energy used, or for a simple way to figure if there is enough oxygen getting into the water.

Phoenix Fish Tank - 25 gallons
With all of my new found knowledge of how I was doing everything wrong in my previous ponds, we decided to get a fish tank and try out making filters on a small scale to start with. We bought a 25 gallon octagon tank and set it up in the living room. I bought a typical aquarium pump that is sort of like a cylinder, in the bottom is a pump, and in the top part you are supposed to put disposable filter pads. I took the pads out and filled it up with small lava rocks. Sure enough, just like all the other web pages said, this filter has been keeping the tank clean. I have to rinse off the rocks about once a month to get rid of the muck, but I sure don't have to buy all those disposable pads. For aeration, I have an air pump and stone. The thing is pretty noisy, so I have it on a timer to run during the day, and it shuts off at night. Later I replaced the pump with an under-gravel filter, and that is even easier to clean and works just fine.



Boat Pond
I really wanted to sink a boat hull into the ground and use it as a pond, but my wife said no way.

The bio filter could be built underneath the bow decking area, and plants could be in pots sitting along the seats. Old fiberglass hulls like this are easy to find, and super simple to repair.