Question about how the filters work and pump size for gravity fed Koi fish pond.

Moobot

Feeder Fish
May 23, 2021
2
0
1
42
I rent a house and it has a concrete Koi fish pond and what I believe is called a gravity fed filter system. (Please bare with me, this is all new to me)

There is a vertical overflow pipe, which takes the water from the pond into the first sump (think that's the correct term). There are 4 of these ground level sumps next to one another and it appears the water moves from 1st one to the 2nd when it gets a certain height and flows over the connecting walls. Then there seems to be a higher wall that separates 2nd and 3rd sump, not sure how water moves there, might be a submerged pipe? Then water moves from 3rd to 4th sump over as wall again.

I can see there is what appears to be small bio balls floating in each sump, but there's hardly any there.

In the last sump there is pipe that come up and out and connects into a large concreate pot which has what appears to be a bag of coral and oyster shells inside.

There is a 2nd pipe in this sump which takes the water back into the pond and optionally up for a waterfall across the back wall.

There is also 3rd pipe, which is t-shaped and also takes the water back into the pond

I believe I need a pump on the pipe which connects to the coral filter to suck it through, but I'm not sure how it goes back into the pond, as this pot seems to missing an outlet pipe connecting back to the pond. Athough there is a pipe with a screw cap at the bottom front and a hole at the top front

I've attached photos. If any one can make sense of this set up, all help appreciated.

My main questions are:

A. Do I just need bio balls in each of the 4 sumps and how many? Do I need to fill each sump? That would seem to require 10000s of them!
B. The pond is approx. 2777 litres in volume, what size pump do I need to filter that amount each hour?
C. Once water is filtered though the coral, how is it pumped back into the pond?
D. I found a device at the bottom of one of the sumps connected to a thin pipe, any idea what this is?

Thanks

1621755521423.jpg

1621755525010.jpg

1621755528261.jpg

1621755531156.jpg

1621755534870.jpg
 

twentyleagues

Bronze Tier VIP
MFK Member
Apr 5, 2017
6,674
9,876
463
Flint town!
The first pic is of an air stone and air hose. You'd need an air pump to run it. My guess with out knowing for sure is that the pipe in the sump (top of last pic) would be a return pipe, needs a pump to send water back to the pond. The sump setup looks standard the higher "walls" probably don't go all the way to the bottom. If they do like you said there is probably a pipe near the bottom to allow water to move to the next chamber. They shells and coral bag is there to help keep water harder. Whether it's a pretreatment for soft water or something that was hooked into your system I don't know. If it was hooked into the system again a pump would be needed to send water from the pond or sump to it and then that pipe would drain back to the sump.
So how I think this all was working or should work based off your pics is
1water flows into the sump from that pipe thing (possibly a bell syphon) in the the pic with your foot the bottom corner of the pond.
2 water is pulled through the sump via a pump in the top chamber and is sent back to the pond.
Where does that green hose go? Is that fresh water supply?
 

Moobot

Feeder Fish
May 23, 2021
2
0
1
42
The green hose just connects to the pipe that goes up and then across the wall to create a waterfall.
 

kendragon

Silver Tier VIP
MFK Member
Mar 23, 2009
5,882
3,660
1,303
The concrete box above ground appears to be for pre-treating water. Might be for holding rain water or aging water. Are you sure the bags of media are shells? Or are they rocks (zeolite). The connection near the bottom of the allows you to top off the water level in the pond when needed.

The hose connected to the waterfall pipe appears to be removable and the right length to reach the hole on the top of the box. Maybe it is in intended to go through the zeolite box when needed. ?????
 
zoomed.com
hikariusa.com
aqaimports.com
Store