CLEANING THE POND

After 4 years of basically maintenance-free operation, a strange phenomenon began to occur. I noticed that the flow of water over the falls was gradually getting smaller. I found that if I turned the filter off for a minute or so and then restarted it, the flow increased again. I figured that perhaps there was some junk building up in the impeller of the pump and when I turned the power off, the water would flow backwards through the system and push the debris out of the impeller.

At one point I even took the pump apart and cleaned the impeller out by hand. But there was hardly anything there.

However, the problem gradually got worse and I had to turn the pump off on a more and more frequent basis.

Then I finally figured out what was really going on.

On top of the 2" filter material on the bottom of the pond, I had placed a very tough layer about 3/16" thick of a kind of weed barrier material. The idea of this was to protect the filter material from debris and I had attached nylon cord to this stuff so I could lift it out and clean it if necessary. All the water for the pump is drawn through this material on the bottom of the pond and it seems that this top layer had finally clogged up with debris. So the pump was working harder and harder to draw the water through this stuff, eventually finding that it couldn't get enough water for a full flow.

So I decided it was time to clean the system.

Because I used to do a little scuba diving, I decided it would be fun to rent some gear for a weekend and swim with my fish. This would also mean I could take the time to carefully inspect the state of the filter material and network of pipes underneath to see how they had fared over the 4 years. And I hoped it would also allow me to work under water more slowly with less disturbance to the fish.


Scuba 1

Getting the barrier layer out of the pond wasn't as easy as I'd hoped. It was covered with slime, weed roots and heavy with water.
However, by rolling the sheets up into manageable sizes, I managed to heave them out of the pond.

I must say how great it was to just be in such close proximity to the fish. They were very tame already and so they would be just inches away from my face where I could really watch and appreciate them. I took some time to just relax and enjoy hanging out in their world for a while.


scuba 3


After removing the 'weed barrier' layer, I was happy to see that the pump ran with great volume and quickly cleared up the water after I disturbed it with my activities. 

Now I'd gone this far, I wanted to look at the filter material itself, and also the pipes underneath.

Removing the filter material really was a breeze .. certainly would not have needed the scuba gear of course, but it was fun to work with it. The filter material, unlike the heavy barrier stuff, easily sheds the water if you lift it slowly out of the pond. I passed it out to a friend from inside the pond with no difficulty. The only issue was whether to let all the water drain out along with the fine debris that came with it, to cloud up the pond. So we drained enough that we could easily lift it out, then lifted it out with as much water and debris as we could.

Once out of the pond I used a pressure washer to clean up the material. The stuff itself is practically indestructible and cleaned up very well, as you can see from the picture.


Spraying 1

Once the filter material was out, the pipe manifold on the bottom was easy to access. I wanted to see the condition of the pipes on the insides, so I took a couple of them apart. I had not glued them in place originally, so I could adjust them or clean them later. There seemed no need to glue them as they are a tight fit anyway and the pump suction tends to pull them together rather than push them apart.

If you look carefully at the picture below, you can see where the exit pipe on the bottom (green) comes up the side of the pond (there's a white section). It then goes up over the side of the pond (covered by flagstones) then down underground again and runs to the pump in the little pump house directly behind the pond, with it's hinged roof open. The pump is below the waterline level so once it's primed, the water automatically feeds the pump by gravity.

pipes 5


I found that there was quite a lot of very fine silt in the pipes, so I figured I might as well clean them out while I was at it. I debated rigging up some kind of vaccuum system to suck out the stuff, but in the end, I decided to just take the pipes apart, lift them out and clean them up out of the water. The pipes are 3" in diameter and have holes in them in two rows. It was a bit messy but once I got the hang of it I found if I moved slowly I could get them out without too much disturbance. Then I emptied out a tasty 'sausage of sludge' from each one which I used in the garden.

Replacing the filter material was quite straightforward as it's so wonderfully light and easy to work with. I just floated the sections on the top of the water and then gradually submerged them as they became waterlogged. Then I could move them into position and secure them with a few pieces of slate.

Because it was so darned easy to work with the filter material, I decided not to try to replace the layer of screen material that I had used in the beginning to protect the filter material. That was what got clogged up after 4 years, whereas I can't imagine how the filter material itself could ever clog up like that.

Filterpad

Now imagine trying to clean out an undergravel filter in the bottom of the pond that used real GRAVEL, instead of this filter stuff! Probably have to move the fish out, drain the pond and get a back hoe. A reely reely big, heavy and dirty job compared to this.

I could easily have done the job without using the scuba gear .. that was just to have a bit of fun and maybe it made it a little easier to work slowly.

It's now 2009 and the system has been working with no maintenance at all for three more years. There are a lot of water weeds (see below) now growing from the bottom and I have left them in because the fish seem to like swimming in them, they use them for laying eggs and it gives some protection against the heron and the sun. And I've kind of come to like them. However, I am wondering how far the root systems have grown into the the filter material. The weeds are easily pulled out but would probably leave their roots behind. But I know I can always lift out the filter sections and give them another clean if I have to, with relatively little fuss.

Pond July 08