Pre-filters and pump intakes.


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I have been learning heaps from you guys, but there are some basic principles about pumps and filtering that I just don't understand.

My pond is shallow (30cms, local regulations), and random shaped, but most closely resembles an hourglass where the two wide bits are around 2 metres across. I have two pumps - one is a fountain style that just shoots water up into the air and let's it fall back decoratively. It has a large (housebrick size)block of foam style prefilter. That prefilter clogs up with algae in a couple of days, and I hose it off with the same rainwater that is used when I top up the pond. The other pump takes water from the pond and recycles it up to a waterfall, via a commercial filter with UV light.

The commercial filter isn't very good, it has a backwash for cleaning, but dirty water never comes out when we try it. We haven't been able to pull it apart to change filter material, and are not sure we could do so without causing damage. So it will be replaced or we will add in an extra filter. I have looked at the homemade filters here, and the principle seems fine, and I think I could make one of those.

Here is where I get confused. I assume I need a pump in the pond with it's own little (or not so little) prefilter to send the water up to the filter proper. The bit I don't understand is how this setup would be any more effective than the simple little fountain pump with it's big prefilter. The pond has lots of string algae and floating algae, which I manually remove almost daily. There is also plant debris such as spent Azolla and pond flowers and leaves, fish poop, and of course the bits of plant material and insects that get blown into the pond. Some of this stuff gets drawn onto my current prefilter and I clean it frequently. Some of it just floats around and some of it sinks. The water that comes out of the fountain prefilter has very few bits left, as evidenced by the fountain clogging only occasionally. But the amounts of gunk in he pond are increasing.

How would a new filter be any better at dealing with the large volumes of algae and plant material? The way I am thinking, the water getting to the new filter would be pretty clean anyway by the time it got through the prefilter. If I didn't have a prefilter, the pump would die pretty quickly from the string algae, and there would be a risk of fishies getting sucked up.

Can someone please help me understand this?
 
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DrCase

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Welcome to the Forum
The main objective is the send the trash to the filter to collect it
I don't have to clean my pump cage very often
 

sissy

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Better to build your own filter only thing those filters are good for is an indoor tank or the trash .You tube has lots of video's of filter builds .Any stuff that stays in the pond that is dead plant matter or whatever will decompose and cause water quality problems .It can be as simple as a tote with a tank adapter and lava rock or a flower pot with the water going back in the pond and filter material inside it
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koiguy1969

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OK. when there is an accumulation of biodegradble material, wether it be fish poop, plant matter, or whatever. the quicker you can remove from the water column, the better. the biomatter doesnt know where its at. if its anywhere in the system it has the same effect. its breaking down, and releasing toxins,( ammonia, nitrite, and nitrates). in fact its likely that it breaks down quicker inside a filter, do to the constant, more concentrated flow of water across, and thru it. so wether you prefilter or allow it to collect in your filter. you want to flush,or clean the collection out. And do it as often as possible without being a hassle..a prefilter is my preference because it catchs the debris before they hit the pumps impellor, get "blended" into a soup. which is that much quicker to breakdown further into toxins. now on a biofilter, the cleaner you can keep the surface area of the bio media the more effeicient the filter will be. a prefilter greatly increases this possibilty.(clean media). this is what makes a sieve setup so nice. as the debris are collected, they are collected, and kept outside the water volume.
** there are several filter build threads right here in the DIY section.
 

Mmathis

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Welcome! I've always been stymied by filters -- my biggest thing is that I want good mechanical [removes all the floating junk] filtration that gets out the particles before the water gets to the biological filtration part. Frustrating, 'cause what works for one person's pond doesn't necessarily work for another... AND THERE ARE SO MANY OPTIONS!

I didn't catch if you have fish in your pond. That would make a difference in your options. If you don't have fish, guessing the "biological" portion [with bacteria that convert fish waste] is not something you need to worry about -- just the mechanical part.

For the most part, those little foam filters are [as you've discovered] pretty worthless. And, since you've done a lot of reading here already, you know that we all have different set-ups, use different equipment, and all for our own reasons.

I have a "SKIPPY" filter. The pump pushes the water DOWN to the bottom of a Rubbermaid stock tank via PVC pipe. The idea is for the water to swirl around in the bottom of the tank where the heavier, particulate material will fall out and collect on the bottom. Then the "clean" water rises through bio-media before it falls back into the pond. I have a drain built into the bottom so I can drain off the gunk that collects.

The very most basic concept here, for mechanical filtration is what's known as a "settlement chamber" -- SKIPPY isn't the best example, however. You might want to look that up.

From what I understand, there are several purposes for a "pre-filter." One is to protect the pump from damage caused by debris, and another is to keep the particulate matter separate so that the water that flows over/through your bio-media is clean [clean, as in there won't be gunk to plug up the bio-media].

I have a "solids handling" pump. My "pre-filter" is that I wrap my pump in Matala filter mats [some here put their pumps in milk crates and surround them with lava rock, or use the filter mats]. Again, a zillion versions of pre-filters. I rarely ever have to physically clean mine -- just pull it up every few months and hose off the Matala.

An advantage to having an external filter is that the gunk that collects can be easily drained out or rinsed off. Since most of us here have fish, we're concerned with both mechanical AND biological filtration.

Hope this helps!
 
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Thanks for the replies.

Turtlemommy, I do have fish. About 50 as the 8 I originally put in bred last year and I couldn't bear to part with the babies. I lose some periodically to birds. For the record, I use an API test kit and my nitrates and nitrites are zero but my PH gets up to 8.8 and my KH is low- after days of adding baking soda I have got it to rise from 5 drops to 6. (107.4). Ammonia is maybe not quite zero, but well below 0.25 which is the first point on the scale.

So, to go over comments so far:

"Skippy filter". Yup, found detailed pics on making them. The principle makes sense. Am talking to DH about making one or checking out commercial equivalents.

"Settlement handling chamber" I can look that up.

"Solids handling pump" never heard that term used. I take it that means the pump will be unlikely to die as the solid material goes through it, and would instead "blend it into a soup". I can look for something like that. It would need to be strong to handle string algae - that stuff is tough.

"Pump cage" and "sieve" . I guess I don't know what these look like. Do you just use the pump as it comes? Or do you put something around it.? How do you get something fine enough to keep the fish out but coarse enough the gunk in? Or don't you have fish breeding in your pond? I can see that burying the pump in a crate full of stones would work, but find it hard to believe you don't have to clean the stones frequently as they are then acting as a prefilter. Maybe that isn't a problem if you don't have a LOT of material in the pond.

Thanks again.
 
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Goodness that many fish will quickly outgrow your pond. You will find ammonia and nitrates will be out if control unless you vet rid if them. I use a very simple method of filtration in my pond. I put a pump near the bottom and run lines to big containers if gravel. The water flows up through the gravel, leaving the debris behind. The water overflows out of the containers, back into the pond. I put plants in the gravel to help with biological filtration. I can see the bottom if my pond clearly, 4.5 feet down.
 
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Look at this little filter box. If you have a pump small enough to fit in the box, this is a wonderful prefilter. I have one, still in use in a stock tank pond, that has been going for 13 years. Since you probably have a pump way to big for this box, get a lidded plastic tote that will hold your pump, and build a prefilter like it. Just cut a hole in the lid for the hose from the pump, and drill lots of holes in the lid for the water to come in. Then cut some good stiff filter pads to go under the lid.

A prefilter doesn't clean the water, but it does remove particles that can clog your pump. If you have a lot of solids in your pond, you will be cleaning the prefilter frequently.
 

Mmathis

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I also use a couple of those little filter boxes for my smaller pumps -- like the one I use for the spitter. In addition to the filter material that comes with it, I usually wrap the pump in some of the polyester quilt batting. I can usually go several weeks without having to clean or change the pads. And they trap a lot of gunk, too.
 
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sissy

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I just put a crate in my pond with the pump inside and bags of lava rock on
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top and only have to pull the bags hose them off and put them back in .I keep it about a foot off the bottom
 

Mmathis

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Bifcus said:
Those little filter boxes look like a good idea, and easy to make and manage.
Thanks.
And see the post before this one -- Sissy explains how she does her's using the milk crate. For larger pumps, that's a good alternative. Another member uses the crates, but lines them with woven mats or furnace filters. I did away with the crate, and just wrapped mine in woven matting (Matala). There are many alternatives to the type of mechanical media you can use, from lava rocks, furnace filters, and various brands of the plastic stuff (like the Matala I use). It's all just a larger version of the little filter box which serves to keep the bigger stuff from getting in the pump and/or messing with your bio-media.
 
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sissy

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I had mine lined with the furnace filter stuff but it was harder to clean all the yucky stuff and hard to lift the crate out with all the muck stuck to it without making a total mess .This way I just pull the bag .So many ways to do it but it has to be easy to get at .
 

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