# Pond Filter DIY



## crocodile_dan (Jun 16, 2012)

I recently completed a home made gravity pond filter, and thought I would post the stages here incase anyone would find it helpful.


Materials:
1x 20L "Handi Pail" food grade white plastic bucket
1x PVC 'T' section fitting
1x PVC length 
1x PVC length for outlet
1x Irrigation fitting Elbow 19mm
Section of tubing/poly pipe
Pond pump
Filter media
River rocks/pebbles

Filter media:
Irrigation Diverter Hose cut into 2cm lengths
Bioballs
Filter Wool

This design is based off of a commercial gravity filter I previously purchased for another system.


Method:

Cut a hole in the bucket near the top (10cm) for the outlet, assemble the pvc length (25cm), pvc 'T' section and the small pvc length with a 45 degree cut as the flow end which comes through the hole in the bucket. This serves as the outlet with overflow See Pics 1 and 2.

Fill the bucket with your filter medium. I used sections of irrigation pipe, then bioballs, then filter wool weighed down with small river rocks. See Pics 2, 3, 4 and 5.

Cut another hole in the bucket ABOVE the overflow (top of the 'T' section on the outlet) and push the elbow joint through the hole, secure in place with a cable tie. This is the water inlet. See Pics 3, 4 and 5.

Attach the hose/tubing to the water pump outlet and the filter inlet. See Pic 6.

The general principle is water flows from the pump to the inlet of the filter where it flows through the filter media down to the bottom of the bucket where it flows up the outlet section and out of the filter. 


Key things to make sure of:

The filter inlet must sit above the outlet and the overflow, this ensures the lowest point the water can travel out of is the filter outlet, and thus has to travel through the filter media.

If the water flow is too great for the filter media the overflow ('T' Section) collects this excess and it passes out the same flow outlet.


This system with my pump will circulate the entire pond at least 3 times per hour (taking into account head flow height) in addition to this filter I have many live plants taking up excess nutrients from the water body.

Filter cost excluding pump but including everything else including clear poly tubing was well below $50 I estimate around $40 (bioballs were the only material I used that was free) and I am using this on an 700-800L pond. The bucket and outlet system alone was under $15.

Any constructive criticism welcome, this is the first I have made but is identical in structure to a commercial model I bought.


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## JAS101 (Jun 16, 2012)

cool write up , and yeah i make my own water filters now . i buy the bio balls and that from ebay , and go from there .


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## mad_at_arms (Jun 16, 2012)

Many thanks c_d, I am currently building an outdoor enclosure for my EWD and this set up will be Ideal for the pond section. I have most of the gear,bar the filter medium sitting around the shed. Bonus!!!


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## adelherper (Jun 16, 2012)

aybe i shall make one for mr ledge haha
the move went well


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## Gypse (Jun 16, 2012)

Awesome filter. I made one about 10 years ago. Almost identical design for a large pot. The pump is 1000l/hr. Mine used a 25-30 litre plastic barrel. The sunlight eventually made the barrel brittle and it broke. The replacement uses a white plastic bucket like yours. The inlet and outlet holes are in the lid for a better seal. My design has a sump to collect dead leaves etc. The barrel design had a tap to drain the gunk but the bucket doesn't. I have a timer and only have it on dawn and dust. Mosquitos only lay eggs in still water and only dawn and dusk. 

There are two little issues with my bucket.
1) The lid leaks air. When the pump runs the presure in the bucket is less than atmospheric. This happens even though the the top of the bucket is below the water level. The bio balls won't work unless covered in water.

2) It's probably not that efficient. The bio balls have lots of surface area but there is not that much flow past them. If the filter was one big long tube with the same number of balls it would work a lot better. That does not fit a bucket very well. Unfortunately the water always wants to take the shortest route from the inlet to the outlet.


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## Sinners121 (Jun 16, 2012)

why not put a couple of spray bars on top? would help to get more filter media touched and therefor a better filter.


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## Cypher69 (Jun 16, 2012)

I was wondering...with both the intake from the pump & the outlet located at the top of the bucket...
Wouldn't it be better to place the outlet at the bottom of the bucket?
My way of thinking is that gravity would take strain off the pump as the water would naturally flow down & out of the bucket rather than have to fill up first.


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## Amazing Amazon (Jun 16, 2012)

Bio Balls are actually designed and work much better if *not* submersed in water but instead are high and dry with water flowing through them. More oxygen means more bacteria. If you place your filter higher than the water level and let it gravity feed back in is best. Cut some plastic or perspex to the diameter of your drum and drill lots of small holes so the water flows evenly through the balls.


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## crocodile_dan (Jun 16, 2012)

Adelherper: you have the commercial one I bought that this design is based on  this one doesn't have to be croc proof though haha

JAS101: Feel free to put some of your designs up. I got the bioballs free from the University of Queensland as they were throwing out their old aquariums for a revamp.

mad_at_arms: No worries, hopefully like some of the post already here there will be some good criticism and suggestions for you to use.

Gypse: Feel free to post a pic of your filter up, it would be good to see for myself especially how you have used a sump with it. All the filter media in this system sits below any holes I've made in the bucket so all media should remain submerged as there will be no siphon effect when the pump switches off. Ideally a network of PVC piping filled with media would be far more efficient, I agree this is nowhere near an ideal setup but cost:benefit ratio I think it is useful. Thanks for your input I will use it in future designs.

Sinners: It would definitely benefit aeration and the spread of water across media making a better filter. I was looking for the most efficient cost:benefit ratio. The number of plants I have in the pond already in my opinion provides a significant proportion of biofiltration, this filter was simply a precautionary measure. I was also concerned about the water pressure that may be exerted on smaller tubing and fitting, currently it has a 19mm tube and if you look at the elbow joint inlet you will see I drilled several holes to hopefully create a shower/spray as it enters the filter, I did think about splitting the flow into two or three 13mm once it entered the filter but I wasn't confident about how it would react to the water pressure. I am relatively new to understanding how this works and the relationship between water pressure and fittings.

Cypher: the inlet for the outlet is placed on the bottom of the bucket, I want the outlet to flow above water level to boost aeration in the pond.

Amazing Amazon: I don't think I will have the pump running continuously so there would not be a continual flow of water over the bioballs if they were not submerged. The perspex recommendation for better water flow distribution is a good tip, thanks


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## Amazing Amazon (Jun 17, 2012)

Pump must run 24/7 in order to work as a biological filter


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## mudgudgeon (Jun 17, 2012)

I recently created a sump type filter for my EWDs water feature, as an experiment, it works great, the water is crystal clear. I will be using similar in my new enclosure that is currently being built.

Google "sump filter" for ideas. its commonly used for marine aquariums where good filtration is extremely important


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## Just_Plain_Nuts (Jun 17, 2012)

great thread ...good work....now you've got me thinking.....


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## TheCheshireCat (Jun 18, 2012)

Instead of bio balls use these

http://img.diytrade.com/cdimg/955275/17941742/0/1294061946/Plastic_Pot_Scrubber_MP1002.jpg

Bigger surface area, cheaper and they last for ever.


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## crocodile_dan (Jun 18, 2012)

cheers mudgudgeon and JPN

TumbleWeed, I tried to source these from Crazy Clarks as I had seen them there in the past but they weren't in stock. The bioballs were free from UQ so I'm not complaining. Cheers


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## cwtiger (Jun 18, 2012)

Great thread, I have an outside pond it is to encourage frogs to come into my yard. I made it out of a wooden vegetable garden put pond liner in it bought pond (frog) plants with drift wood. Have all sorts of bulbs growing around on the outside. Carpenter frog moved in laid eggs very happy. Pond water was getting dirty so bought a pond pump well it look attractive but doesn't clean pond only gets clugged from all the dirt frog's have put into pond. Was trying to think of a way to filter pond will try my very useless hand at some of your filtering systems. Thanks for sharing.


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## mad_at_arms (Jul 15, 2012)

So if the pump isn't running 24/7 is there any benefit to the bioballs?
I am building one at the moment and was going to use scoria and polyester pillow stuffing as my filter mediums.


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## crocodile_dan (Jul 15, 2012)

My understanding is bioballs are just designed to increase the surface area for bacteria to colonize, any filter media will provide a surface for bacteria growth. I was operating under the assumption that if the filter media didn't dry out then the bacteria would still survive. You also need the filter bacteria to be aerobic.
Having the filter running 24/7 would maintain water and oxygen flow across the filter media surface, stopping flow would mean the water is sitting around the media and possibly cause anaerobic respiration if the oxygen in the water is consumed.

Please someone correct me, this has been my understanding for some time now meaning I haven't reexamined this topic for a while now, so I'm happy to be given corrected information. Cheers


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## melluvssnakes (Jul 16, 2012)

I assume these designs are meant to be above ground filters. ie. the actual canister sitting above the water level for gravity feed. I wonder has anyone designed on that could be buried to keep out of sight? Would it just be a matter of inserting another pump into the actual canister to push the water back up and out?


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## dangles (Jul 16, 2012)

seen the same setups made out of wheely bins for above ground turtle ponds. They also had uv clarifiers installed into them


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## mudgudgeon (Jul 17, 2012)

melluvssnakes said:


> I assume these designs are meant to be above ground filters. ie. the actual canister sitting above the water level for gravity feed. I wonder has anyone designed on that could be buried to keep out of sight? Would it just be a matter of inserting another pump into the actual canister to push the water back up and out?



either. The pump needs to be at the lowest point of the system (impellor type pump).
You can have the sump below the water level in a pond,with the pump in the sump. Or, you could have the sump above a pond, but would need a pump in the pond to pump water up to the sump, which then drains back to the pond.


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## Amazing Amazon (Jul 20, 2012)

melluvssnakes said:


> I assume these designs are meant to be above ground filters. ie. the actual canister sitting above the water level for gravity feed. I wonder has anyone designed on that could be buried to keep out of sight? Would it just be a matter of inserting another pump into the actual canister to push the water back up and out?


You can have them either higher or lower (sump style) as long as the water gravity feeds from one end i.e you cannot pump into filter and pump out of filter as you will never get the flow rates exactly the same. If it's not on 24/7 you are wasting your time. Alternatively if it is fully sealed (airtight) you can put it anywhere you like, pump into it, through the media and then back out again. There are lots of these type on the market ( Pond One and Laguna) to have a look at.
Here is a picture that might explain the sump style better


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