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FAQs on Pond Filtration

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Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

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by Robert (Bob) Fenner

How do you make pantyhose safe to use around fish?       2/13/15
I need to find a replacement for a fine silt sock for a pond vacuum. I was looking at using pantyhose. But I need to make the pantyhose safe to use around fish. How do I make pantyhose safe to use around fish? Thank you.
<An old school approach for bagging up carbon and other media. Simply rinse them thoroughly, avoiding cleaning products because they can be toxic. "Media bags" are widely sold, and my be preferable if you aren't comfortable using the old pantyhose/tights. Cheers, Neale.>
re: How do you make pantyhose safe to use around fish?       2/13/15

Thank you Neal! :)
<Glad to help.>
Pantyhose again     2/14/15

If i use dyed pantyhose for a filter sock replacement for my pond vacuum's filter sock, do I have to treat them differently than pantyhose with no dye?
Do I need to bleach dyed pantyhose if I use them in my pond? Thank you.
<Likely no need; but I'd use Dacron/Polyester bags made for the purpose instead. Much tougher; less likely to tear, spill... Who makes, sells
Oh; a fave: Emperor Aquatics: http://www.emperoraquatics.com/gravity-and-pressure-bag-filters.php#filter-specs
Bob Fenner> 
Re: Pantyhose again      2/15/15

Thank you Bob! :)
<Welcome Cam... the swimming pool/spa industries also sell "vacuum bags" of good quality and strength; though they are likely "too coarse" to be of best use for a biological pond. BobF>

Pond During Pool Construction      2/27/14
Just wanted to share this with you. Are pond during the construction of the pool.
Picture below.
The pond is the thing under the blue tarps. All I can say is with all the dust, thank goodness for tarps. 

re: Pond Preparations      2/27/14
Unfortunately, leaving the filter on is not an option. I can only try and plug the filter back in when they finish digging tonight or tomorrow night.
The fish have been without the filter since yesterday afternoon. Will the fish survive until tomorrow night? Thank you.
<Likely so... see WWM re pond filtration... best of luck. B> 

String Algae in a <pond> filter 8/5/11
Dear Crew,
<Hi Allen>
In lawns and gardens, the definition of a weed is simply any plant that grows where you don't want it to grow. My pond filter basin is growing a healthy coat of bright green string/hair algae that would be terrible if growing in the pond itself, but it doesn't bother me in the filter basin. I know that people often brag about fields of "lush green algae" when growing in the right places.
<Ah yes>
So my question is this: is that bright green string/hair algae inherently detrimental? Or just a weed when it grows where we don't want it?
<The latter in almost all cases. There are some quite toxic algal species (esp. some of the Blue Greens), but their preponderance in healthy pond settings is exceedingly rare. Better by far to have desirable species proliferating in an area where they cause little visual distraction, are easily harvested...>
Thanks for your great service.
<Welcome. Bob Fenner>

Re: Pond enquiry, Filtr., ducks 6/30/11
Bob, thank you so much for all your assistance!
<Welcome Kim>
I will give this a go & hope it all works out!
Kind regards
<Do please review the few olde articles and our FAQs files re pond filtration... Linked here:
the fourth tray down... And feel free to write back w/ questions, comments, concerns re.
Cheers, BobF>

Pond Rehab Query 4/22/11
Greetings from Charleston, SC!
<Hey Mitch!>
I have a customer who has a concrete pond
measuring 20'Lx10'Wx4'D. Being that we are below sea level, and having a fairly small yard to work with (He lives in the city) and being that it is a concrete pond, we are trying some alternative approaches to filtration. He has no filtration,
and has asked me to work up the best solution. (We are attacking the filtration, then when the pond is functioning, we will move on to aesthetics.) He does have a large UV sterilizer,
<One that I hope/trust has sleeved lamps>
so that is one less item we will need.
<A note: Your improved diagram depicts two ball valves to isolate, service the UV. You need a third... to direct some/all the water through the unit... in the plumbing line above the UV>
I was wondering if you could provide some insight to how we should approach some issues. I have found some In-Pond skimmers (Easy Pro Eco Series) that will work for the surface debris, in conjunction with a high flow solids-handling pump.
<Mmm, do be careful here... You really do NOT want high pressure along w/ high flow... better to use half speed pump/s...>
(The in-pond skimmer is the same as one you would have through a liner when a pond is excavated, it just eliminates the need to demolish the concrete and serves the same purpose.)
<Thank you for this; am familiar>
I was interested in the potential of 1-2 "retrofit" Bottom Drains. I was hoping you with your expertise in this field could give me some insight/suggestions.
<Mmm, better to not rig the pump intakes to such lowest areas, but instead to "pick up" recirculated water about at half depth... Do place plumbing/drains (if it were new...) to be able to vent or periodically pump, drain from such "bad water" areas, venting solids that accumulate there>
I have considered plumbing from the bottom drain(s) to a bulkhead through the skimmer (near the bottom), adding a basket or sieve to collect the debris so it does not clog the mat (post primary skimmer basket). (Unfortunately a settling chamber is a difficult proposition, otherwise I would run the bottom drain(s) to such a chamber).
<Ah yes>
Does this sound like the direction I should pursue?
<Again... I would just (during the summer every few weeks) pump from the lower drain areas... but a plumbing manifold could be arranged to pump from them. I would not recirculate the lowermost portion of the water and the accumulating debris from there>
So, from the bottom drain(s) and skimmer weir, through the debris baskets and skimmer pad, through the pump, out of the skimmer.
<And as w/ swimming pool and spa use of such skimmers, do have a smaller diameter, alternate intake to the pump... lest the skimmer basket, filter media become too clogged, the water level be too low...>
Then we are routing the plumbing T'd straight to the waterfall with bio-media, and the other side of the T is going through the UV sterilizer with a ball valve to reduce the flow for optimum UV performance. I am still unsure as to
how we are going to design/implement the main biological filtration. I have been reading, re-reading your articles in the Ponds Construction/Filters/FAQ's and would like your personal take on this issue.
<All I know is archived on WWM... the bigger the better, fancier, one-time-purchase media better by far than rock...>
Does this sound reasonable for filtration of a hybrid Koi pond/water garden?
I have attached a crude sketch of the general plans for the filtration. Do you think it is okay to have the return plumbing in the pond up to the filtration on the upper left hand portion?
<Yes... you can paint it to match... algae will grow over, conceal in time>
(We intend to hide the PVC with plants for aesthetics.) Yes, there will be plants (mostly floating islands) and Koi (minimal stocking). I truly appreciate your time and any suggestions you may have.
Thanks in advance!
(P.S. Thanks for your help on the other issue I had with another customer with the bloated goldfish. We are considering bringing the affected fish to our local exotics vet to have blood drawn, cultures run, etc.
<Mmm, again, I suspect there really are no principal pathogens at work here...>
Either way, he
knows now that he needs both proper filtration/environment/husbandry, as well as the proper diet. And I also found a commercial pond pellet with around 10-11% protein and 4-5% fiber! Thanks again Bob!)
<Welcome! BobF>

Re: Pond Rehab Query 4/23/2011
Thanks for the suggestions Bob! I am more and more leaning towards building a good upflow filter for this pond.
<Better than down flow for sure>
I have used these before in my last job as a LFS retail manager. They seemed to hold up fairly well with minimal maintenance (with proper/thorough mechanical filtration in place of course!) The only question I have in regards to this is the way the pump is affixed to the filter. In my previous store, the pump was T'd off with a ball valve going into the aeration tower, with the rest of the water going back to the display tanks, and the overflow from the upflow filter going back into the sump. I am guessing I should have the flow directly into the aeration tower at the top portion, still T'd off to the UV with a ball valve to control the flow to the UV. (Yes, the UV does have a coated quartz sleeve)
<Mmm, I'd trade this unit out... for sure... for one w/ this mat. or Teflon sleeving. The TMC Vectron units are my fave... can be gotten through Quality Marine in LA... the one you have there does not really work when the water is cool temperature... Most all the time>
Now, I believe the volume of water from the overflow (at the top of the upflow filter) will be enough to power the waterfall tank... Do you agree?
<With an "adequate" pump (see WWM re) and plumbing diameter (likely 1.5 or 2" ID) it should be>
I was also interested in what you meant by recirculating the water from mid-water. Should I have some sort of screen over the inlets, or other protection so fish don't find themselves in a pipe?
<Yes, assuredly>
Or should I just run a
45/90 degree fitting at the end of the inlet towards the wall of the pond?
<Do use screens>
And I have been reading more on pumps, and I am still in-between several different models. Submersed solids-handling/External with check valves to keep prime/Self-priming external...
The possibilities seem endless! I need something that is reasonably priced, but gets the job done.
<VERY important to realize the real cost (operation) here...>
If I were to turn over the surface area once per minute, I would need a 12,000 GPH pump!
This seems a bit much to me, I was thinking something closer to 6,000 GPH.
Any suggestions?
<Yes: Sequence... also avail. through QM>
I want enough flow to power the filters and waterfall; to keep the pond clean and healthy, have a calming waterfall sound. I don't want the customer's backyard transformed into Victoria Falls! Thanks for your time and all you do!
<Again and ongoing welcomes. BobF, out to the desert>

Do you have a favorite or recommended filter for 5000-6000 gallon pond? 8/6/10
I am in market for a good filter for my 5000-6000 gallon pond.
It's 30'by 12'by 3' deep although a 2 foot ring around the pond is only 1 foot deep.
<Mmm, okay... Please read here: http://wetwebmedia.com/PondSubWebIndex/Pond%20Sub%20Web.htm the first tray>
I have had this pond for three years now and don't have a filter on it. Have a hundred small 3-4 inch fish and a dozen Koi. Winter algae dies and is clear, summer is mess, mostly because I don't have beneficial bacteria and water gets really green. I imagined that the algae are good for the fish. Have three waterfalls into it that seem to provide good Oxygenation. Want to see fish year round though now. Matt
<Keep reading... further down... re pond filtration. B>
Re: Do you have a favorite or recommended filter for 5000-6000 gallon pond? 8/6/10

I read this but didn't see any specific recommendations for filters by manufacturer. Is there a good, reliable filter that you'd recommend. Matt
<... not w/o more specific input from you... Many folks nowadays run powerful sleeved UVs, even ozonizers to stabilize water quality... Bead filters are very nice, though pricey to acquire and operate... Conventional reverse flow, substrate types are still my historical faves, coupled with integral, in-line, ahead sediment chamber/s and brushes. B>

Canister filter placement, pond... subgrade? 4/15/10
Hello! Love your site. Thanks for all the helpful tips.
<Welcome Jack>
I have an issue: this is for a pond. I bought a new canister filter (JBJ EFU-25) not even thinking about placement. Obviously, since I can't move the earth, the canister must be above the water line.
<Mmm... the canister filter pump really needs to be below the water level of the pond... you could dig a hole, place a plastic irrigation box nearby... Or I'd be looking for another filter. Possibly modifying the canister by placing a submersible pump in the lowermost basin (if there's more than one), and pumping to the canister filter inlet outside the pond... running the discharge to a distal point>
I can get it running for a while, but it will lose its siphon. Is there any reason why a pump can't be used to get water to the canister?
<As stated above...>
I know these are meant as gravity-feed filters, but would a pump do any harm?
<Not really... as long as the "net" pressure isn't too great (the top blowing off), a submersible pump may be just the ticket>
Thank you for your help.
jack Wallen, jr
<Welcome. Bob Fenner>

Chicken Grit, pond filtration 6/4/08 I just built a new pond. Its about 25 feet long, 12 feet wide at the widest, tapering to 5 feet wide at the narrowest. It's 18 inches deep at the narrow end tapering to 30 inches deep at the wide end. It's roughly 2200 gallons. I'm using an Ebara pump, rated at about 4300 gph to an 18 inch Hayward sand filter filled with 100 lbs of crushed granite Chicken grit. The pieces are roughly 1/8 inch to 3/16 inch. <Mmm> I've only had the filter up for a couple days and the water is starting to clear. I saved about 100 gallons of my old pond's water for a bacterial boost. <Good technique> Unfortunately we've been hit by torrential rains since I filled my pond and have been unable to complete the waterfall or anything else, yet. I was wondering how well the crushed granite would perform over pea gravel. <Both can be problematical... in terms of "compacting" and channeling... lighter media is highly preferable> The pea gravel sold in my area is more like ½ to ¾ inch gravel and with pieces that large, I don't see how they will do much filtration. I backwashed the filter this afternoon and the water was still relatively clear. I don't have any fish in this pond yet. My son managed to catch all my Koi from my old pond and carry them like a squirmy bluegill to the horse tank for safekeeping. Unfortunately they died from the trauma of an overzealous teenager's handling. Any idea you can throw my way would be most appreciated. <Best to scoop up not-so-handled "medium" (a foot, foot and a half) Koi in thick (4 mil.) fish bags (see your dealer or save old ones) and move with minimum water. Larger Koi still, esp. ones that have been handled from time to time, can be picked up, carefully, from underneath... there is a great deal that can be related re technique here> I'm kind of a jack-off-all-trades, and I prefer to make whatever I can. My drywall bucket bio prefilter is my first engineering marvel and is still in use in my new pond. It's installed after the mini skimmer with a 900 gph pump discharging toward the waterfall site, so there aren't any dead spots. <Ah, good. Again, I would look into "more appropriate" filtration methods here period. Pressurized filters, the pumping to run them... is too expensive and inefficient in this day and age... Do check out the Net, libraries for modern books, articles on other means. And we'll chat if you'd like re. Bob Fenner>

Pond construction... no filter...? Reading... 3/9/08 Hello Mr. Fenner- <Kate> I am in the preliminary planning stage of constructing a round concrete and block pond with approximately a 7 foot diameter. Is a filtration system an absolute requirement? <Mmm, no... not absolute... Can be made to be some sort of "balanced"... rely on other means to keep it "clean"... periodically...> We want a fountain feature and some fish. Are there self sustaining alternatives to a 'formal' filtration system? Please advise, Kate Miller <Mmm, planted in a few ways... I do encourage you to read a bit re... at least use an intake screen type on the pump/ing mechanism. Bob Fenner>

Koi pond filters 8/8/07 Hello Mr. Fenner! I was the one with the 4,000 gallon Koi pond project. I have already dug out the spot for the pond, I got one external pump (Dolphin 4500). I'm now in a debate with my wife over what type of filter to use. If it was up to me, I have obtained four of the 55 plastic barrel drums. <Mmmm> I intend to use three of them in series (they'll all be hidden of course!), and make my own filtration system. My wife wants to get the Nitramax 6000 (Pressurized filter) which cost about $600. What's your take on this? Is the maintenance that much harder if we opt for the barrel drums? <The commercial unit is superior... function and maintenance-wise. I'd really like to have a redundant bio-filter of size as well... Like those (generally built before the main pond basin/s) detailed on WWM... Bob Fenner>

Vortex DE filter on a pond... 6/20/07 Hello, my question is regarding my diatom XL. I had the same one for 32 years and it finally seemed to be slowing down. I purchased a new one. I run it on my 200 gal outdoor pond. <Wow... has to be cleaned very frequently... this unit is not designed for this application, nor continuous use...> It runs for about twenty minutes and then stops. The pond sits out of the ground about two feet. The diatom sits on the ground, and both hoses run up to it. <Mmm, also not made to "pull" water uphill...> If I take the exhaust hose out, put it on the ground it start to siphon again, but the suction hose always has air in it, and then it stops again. What am I doing wrong? Thanking you in advance....Pookie O'Donovan <Mmm, could be a few things... But allow me to skip ahead and just encourage you to read here: http://www.wetwebmedia.com/ See the link to pond articles? Bob Fenner>
Re: Vortex DE filter on a pond... 6/20/07
Hi, thanks for the quick response. Checked that site, didn't see anything related to my problem. Checked vortex site, according to that, as per usual, hoses must run up to tank, mine do, run up to the pond. At this point I might just throw the thing over the fence into the creek, (if it's possessed maybe it will run, and filter the creek water.) Thanks anyway.. <Mmmm, but have you considered a "real" filter here or? There are various types proposed on the site... Again, the Vortex product is not designed, engineered to work outdoors... or to be run on a continuous basis... nor to operate above the water level of the system... Do come back and read when you have time, interest. BobF>

Question about sick pond goldfish... Mmm, and Pond Circ., Filtr., Maint. 8/7/06 Hi - I could not find the answer to my question on your web site and hope you can help. <Will try> We have a natural outside pond. It is under shade all day and has much foliage around it but none in it other than the occasional foliage which drops in from around the pond. The pond measures aprox. 26 ft by 14 ft by 4 ft deep. It is always clear and is fed from the runoff of our spring box. <How nice!> The water is constant circulating and has a pipe in the middle of the pond to control overflow. <Mmm, I would "sleeve" this... put a pipe over this one, notched at the bottom... to "force" "old water" and silt from the bottom rather than venting newer water from the surface> There is a dirt bottom and a layer of leaves. Also at the bottom is a very small spring which additionally feeds the pond. <Great> I am not sure how old the pond is, we have lived here 5 years and it was here when we bought the home. The only upkeep is the removal of leaves every 2 years or so. The current gold fish we have in the pond have been there 3 years. We originally had five. <No reproduction? Odd...> Just this past year, around the beginning of spring we lost one fish and now, recently, a second. The goldfish both measured about 6 to 8 inches long. Prior to dying, they both became lethargic and kept themselves close to the edge of the pond. Resting themselves there and not swimming around at all. They also lost many of their scales and where the scales were, there was "fuzz". <Perhaps... secondary... decomposition> We are worried there may be a disease or parasite in the pond. <Mmm, not likely... or at least not likely a primary cause/source of mortality here. Much more likely is some sort of environmental complaint... most easily addressed with the added "sleeve" over your standpipe mentioned above...> We are also concerned that the problem may be at the source spring. <Mmm, yes... and/or some bit of decomposition in the "overburden"... the unconsolidated "ooze" at the bottom... again, best addressed with the sleeve, periodic increased (over)flow from rain...> This is concerning because we use the water from this spring for our home use. It is a separate spring box pumped to our home but the overflow from this spring feeds the pond. <Mmm... Am sure you have particulate and chemical treatment to make this safe, potable... If it were me/mine, I would make use of a reverse osmosis device for potable uses... adding a "booster" pump for need pressure if required...>> Any help you could give would be greatly appreciated. Thank you. J.M. <Welcome. Bob Fenner>

Inquiry into the effectiveness of ozone on a Koi pond. 9/30/05 Hello, <Hi there> If I somehow missed the article on Ozonizers in ponds in your database, please point me in the right direction. <Mmm, unfortunately, I don't think there is such... but have installed them, seen them in use on many large/r ponds> I have a customer who is looking for increased clarity/oxidation in his heavily stocked (and extremely dirty) Koi pond. I have not seen the pond myself, but he describes it as being 2200 gallons in size and he does have a sump. I have heard that you can put protein skimmers on ponds also, and I'm wondering if we should try both? <Mmm, skimmers are generally not worthwhile in freshwater use... particularly in hard water conditions... not enough foaming... There are some really innovative "partial pressure" contactor and collection cup designs (See Sander re if you'd like, can read German), but better to have just the ozone> My questions are- 1.how effective will either actually be? <The O3 can be a tremendous boon... burning up nutrients, virtually destroying all free-floating algae, and reducing attached types tremendously... while improving the looks, health of the livestock> 2.In your opinion, which ozonizer would be the best to obtain? <Depends on the size of the pond, your budget... look on some of the "Koi pond" websites... for anything of size, the corona-discharge moda are better... Bob Fenner>
Thanks so much, Niki_CoralConnection

Pond Filter Question 7/30/05 Hello Bob, I have a question pertaining to my mother in law's pond in her garden. Her filter keeps on getting clogged with moss or algae (however you spell it). The pond is around six feet long by three feet wide. It is around two feet deep and contains three fish. The fish are two goldfish of about 5 inches apiece and a rather large minnow which is 4 inches long. Her filter is in the middle of the pond under the water and she keeps having to unclog it which is apparently a large task. <Very common... real trouble with in-pond filters... especially cheesy intake types... don't work... and are dangerous to enter the pond to service (be careful! Slippery city)> We live in south central Texas so I was wondering if maybe our climate has anything to do with the rapid growth of the stuff? <Assuredly yes> Its pretty hot down here and often very humid or very dry, depending on the day. Temperature range from 95 to a good 105 during the summer so its pretty warm. I was wondering if you could possibly help me with the problem. I know the fish eat the stuff, I think, so naturally we don't wish to kill it all, but maybe tone it down a little. Could you possibly prescribe a solution to our problem? Thanks, Jesse and Melissa Bell <... please read... starting here: http://wetwebmedia.com/PondSubWebIndex/pndfiltrovr.htm and on to the linked files above... and on pond algal control... there are a few routes to go here.. shading, purposeful competition... your mom needs a better filter as well. Bob Fenner>

UV filtration needed (for large natural pond)? 7/16/05 Hi there. We just dug a pond, approx. 35 X 60 feet, 8 feet deep max, with one corner to be a wetland. We are beginning to plant it with local vegetation today. The pond is not lined, but has had rubble (3 to 4 inch diameter) added inside to stabilize the banks. <... and percolation? Oh, see you've addressed this below> There is a small sandy beach. Dug the test hole last year and it holds water. The pond is actually dug along the path of a natural drainage channel, at the base of a 20 ft rock wall. (pics to follow) Anyway, we have raised the natural water level about 2 feet. Approx 50% Clay soils, so retention will be OK. However, the source of the added water is a stream. I know Coliform and other critters are naturally occurring in any surface water system. <Yes> The stream is thick with aquatic vegetation, a sure sign of nutrients I would imagine. We are drawing water from further upstream to get the cleanest water possible. But once it hits the pond, it's wide open, sunny, and I would imagine bacterial growth will take off. A few questions: 1) Should we use UV filtering. Won't this kill all bacteria including beneficials? <Mmm, I would not use ultraviolet here... but would definitely look into ozonation directly> 2) How much area should be wetland or vegetation? <At least ten percent> 3) How do I stabilize the sandy beach which right now is like quicksand? <Mmm, depends on composition... would have a soils engineer, firm... depending on the make-up, you may be able to just add a bit of silicate, carbonaceous material to make this area more "solid"... at the very worst, a berm might need to be emplaced and the area back-filled with a suitable substrate> We will be running two waterfalls, one a height of 20 ft. <Wowzah! Do be careful re pump selection, operational cost here> and the other just a 2 foot rise over 6 inch slabs (kind of like steps) with gravel and sand. Pump rated for 5000 gph, but will probably get about 3000 after friction loss/head. We were also thinking about making a type of sand filter out of a couple of apple juice barrels! <... likely not worth doing... will clog very quickly... and w/o a very easy backwashing mechanism will be ignored, abandoned in short order> I have to say I am excited about discovering this site. So far, my biggest problem seems to be the lack of consistent info. Example, the pump manufacturers said I need 10 pumps running in tandem!!! <Heeee! Geez!> (I think not) It's hard to know what to do. Any help would be appreciated. Noreen <Glad to share. Please make it known if this/these communication/s aren't clear. Bob Fenner>

Pump and no "filter" 6/29/05 Hi, <Hi> I have read many of your FAQs and didn't see the question I had. so, I have a 3ft. deep oval pond, 3x4 feet across and I'm pumping the water through a tube up to a 20 foot stream that is concrete with gravel, some loose, some imbedded, and then it flows back into the pond. I also have a small pump that I just keep completely under the water and just pumps the water around to create circulation. The large pump is about 1ftx1ft, don't know how many gallons it pumps, but quite a bit. <Submersible I take it... have you measured its energy consumption?> Since the water flows over the gravel and back into the pond, and I have two pumps with just the filters that come in the pumps (foamy stuff with little round beads), <These are actually more accurately termed "intake strainers"... they don't filter the water per se, but keep objects out of your pumps volutes> do I still need a filter? <Mmm, maybe, maybe not... the stream, gravel do provide biological filtration... is your water "clean" enough to suit you?> I know I don't have the most ideal set up and I'm on a strict budget. I have tested for pH and is about 7.5-8.00 <A bit high, but...> I have 15- 1 inch goldfish, 4- 3 inch goldfish and 4- 5inch goldfish and one smallish water lily. Thank you for your time. Denise <Mmm, a few things to say. One, I would have a friend who knows about practical matters with electricity test for electrical consumption (there are "wrap around" non-invasive techniques, gear for this... You are likely paying a great deal more for your pond than you are aware. Two, take a read through WWM re pond filtration: http://www.wetwebmedia.com/PondSubWebIndex/pndfiltrovr.htm and the linked files above where you lead yourself... As your goldfish grow, and you find yourself feeding more... it may well be to your advantage, desire to fashion or buy something in the way of more filtration... mechanical, biological... maybe even a physical component. Bob Fenner>

Pond Filter Design Hi Robert, I read your article in Wet Web Media.com. I think your ideas make a lot of sense. Do you have more details on the construction of this simple idea including the filter media to use. <Do... in my files at the S. Cal. res... but am out of town... Are you looking for something in particular? We started with encouraging folks to use crushed rock, graded... some people advocated the use of igneous... we eventually found, cut with a band saw, plastic honey-comb used in cooling towers...> Thanks in advance. I'm installing an 1100 gal fiberglass pond. Best regards, Horst Riedner <Bob Fenner>

Help on Pond Filtration Thu, 17 Mar 2005 Dear Sir I need your comments and suggestions. <Okay> I'm working on the algae prevention of our pond. Crystal clear water is essential. A 1800 m3-pond will be constructed. We think a system circulating and partially ventilating all 1800 m3 still pond water in every 12 hours-period. We think quartz sand filtration with three or five layer down to 40 micron size to prevent algae and an additional precaution to prevent algae, electrophysical disinfection system (dispersing copper iron) giving 12 Volt current to kill algae passing through it (after the filtration the water will come here). Does this solution become effective and sufficient especially in hot July and August months as well? <Mmm, no... is this a biological pond or one that is to be poisoned? If the latter I would go with more simple hypochlorite bleaching with an isocyanuric conditioner, some pH manipulation (all this similar to swimming pool sanitization)... IF it's intended to house fishes, plants, the quartz filter media will clog, channel too badly and the copper be too toxic... let's keep reading> If it is not sufficient should we [add] a diatomite layer onto filtration layers add in those months ? If fishes are added is this system sufficient without nitrification ? <No... the diatomaceous earth is a very poor idea in biological systems... it will clog almost immediately... and be difficult to backwash, clean... And all biological aquatic systems require provision for sufficient nitrification...> (In the other side, is biofilter utilization effective instead of above suggestion for 1800 m3 circulation in every 12 hours ? What about bacteria efficiency in application, maintenance and seasonal conditions?) <I understand what it is you seek... clear water throughout the year... for a living pond... You can best achieve this through the combined use of a good-sized (large, at least ten percent of the pond volume) biological filter AND the use of ozone, likely through ultraviolet sterilization... These matters are dealt with in general articles (on pond filtration) by me posted here: http://www.wetwebmedia.com/PondSubWebIndex/Pond%20Sub%20Web.htm. Please scroll down to the section on Pond Filtration, read there, and re-contact me with your specific questions if you'd like> We must give correct decision. In advance I am thankful for your leading suggestions. Best regards Canan Girgin <Thank you. Bob Fenner>

Pond aeration Hello crew, <Karun> I have just started a small pond 5ftx5ftx1.5ft. I am using an Eheim filter that circulates 3000 litres /hour. <Great units... do just make sure the electrical connection is out of where it can get wetted> The pond has assorted plants. I also have about 30 mollies and guppies and 8 red tail black sharks (2 inches each) The pond does not have too much surface movement and no aeration. Will there be enough oxygen in the water? Should I increase the surface movement? <Good question... I would arrange the discharge "wand" to either discharge some of its "hole/outlets" above water, or at least for the water surface to be rippled by placing it, turning it to discharge near the water surface... alternatively, if you have the means, a good air-pump (my favorite choice, the Tetra Luft series) and maybe attach this to a sponge filter... would be ideal for both added aeration, some filtration, and redundant back-up. Bob Fenner>

About ready-made pond filtration Hi, <Hello there> I have been an avid reader of your website for a long time now, and hardly ever change anything in my FOWLR tank without first going over your FAQs,. Now I am starting a new project, building a 1500 gal. pond and since I am quite unknowledgeable in this area, would like to know if the filters/UV systems on the market are any good, or if not if you have any suggestions for a ready to use filter that will be easy to install. The pond will have a fountain, which I think can use water diverted from the main pump. Any help will be much appreciated. Thanks! Harold Chamberlain San Jose, Costa Rica <Good question. Some of the available, pre-made pond filtration is excellent, some passing, other components more gimmicks than useful. Look to the largest size volume units possible, practical for your setting and size system. Large amounts of filter media, automated or semi-automated backwash mechanisms are a special added plus. Check online and if possible first hand with people who are using the given technology and products. Ultraviolet sterilizers can be of highly variable quality. You definitely want a "sleeved" variety (quartz or Teflon, not the bulbs themselves exposed to the water, even in the Costa Rica capital where it's generally warm to tropical)... and somewhat matched to the rate of flow, diameter of plumbing of your pump/s... likely at least 100 watts in power. Do investigate other factors in filtration, maintenance of ponds before proceeding here. Shade, position of the basin, surrounding landscape, careful selection of foodstuffs... the types, amounts of livestock chosen... all play critical parts in whether your pond will be clear, healthy or no. Is there a pond club/society, perhaps a few folks in a botanical group who keep ponds as well that you can visit, chat with re what they've done, would do in <re)designing such a feature? Their experience, reflections would be invaluable. Once you get a working drawing of what you will employ drawn out, please send it along for review. Bob Fenner>

A duck and goose = dirty pond I initially got a 175 gallon flexible liner pond for water plants (lily's) and maybe small guppies. However in the meantime acquired a duck and a goose, both about two months old. Well guess who is in the pond everyday? <Bad visual> I have to replace the water every day or two. I want to keep duckweed in another receptacle to feed them because they'll eat it up before it can clear the pond. What other filtration system can I use on a pond this small-or do I have to build them a lake!? <More likely the latter. The 175 gallon volume is way too little to even try to filter, keep one waterfowl/foul... I would keep changing the water. Bob Fenner> Rita De Ferrary St. Thomas, VI

Pond Filtration Mr. Fenner, <Mr. Jordan... any distant relation to the minor prophet of democracy, first president of Stanford University, hero of mine David Starr Jordan?> I have been reading your site for a couple of years now, and you guys have answered quite a few of my question about marine aquariums. I appreciate your information, especially since it is not biased by the need to sell me something I might not need. Anyways, I recently purchased a home, and after building a deck, I am going to build a pond to go around it. It will be about 4 or 5 feet wide, and three feet deep along the outside edge, with a foot or so deep shelf on the deck side for aquatic plants. <Make it more like a foot and a half> I'm still in the early planning stage so I haven't multiplied out the dimensions for a guess at capacity yet. I've read most all of the FAQ's and other info on your site about ponds and filtration for them, and have a few questions. <Okay> 1. I would like to make my own filter for budget reasons. How does a 55 gallon plastic drum filled with washed gravel sound. The gravel here in Mississippi is primarily quartz based, with a few other things thrown in. I read about the reverse flow (bottom to top), but was wondering how it well it would work it a wet/dry format, with a diffused spray of water coming in the top, and trickling down. I would leave a foot or so of void in the bottom with a drain to periodically removed accumulated materials. The outlet would be, say two feet from the bottom so some of the gravel would be submerged. <Worth trying> 2. Could you give me an approximate GPH or GPM flow rate for a filter this size, or some sort of formula to use once I figure the pond's capacity? I have a Little Giant that I'm not using that flows 900-1000 GPH and would like to use it if viable. <Sure... about ten gallons per cubic foot of filter material maximum (this is an average maximum flow rate per...). Little Giant makes a range of pumps....> 3. I read that filter size should be based on surface area as well as total capacity, that the filter should be 10% of the volume. Is too much filter detrimental? <No, only the opposite> If not, could extra the extra filter be a safeguard, of sorts? <Yes> 4. Also read about the use of lime, could limestone also be used in this fashion? <If necessary... that is if your water is deficient otherwise in buffering capacity... If you have some hardness/alkaline reserve I would avoid alkaline filter media> Seems like it could serve as a buffer, dissolving as the pH drops, unless it would dissolve anyway and raise the pH. <You are right here... the biological and chemical processes in a typical gravel filter are reductive in nature... lowering pH and alkalinity...> I had some more questions, but lost my train of thought. I'll get back with you later. <Real good. Will be here. Bob Fenner> Thanks, John Jordan

Large Fish & Large pond filtration 7/29/04 Hi - I have a 25 thousand liter pond in the tropics of Australia Far North Queensland. I have (or had until recently) 7 large barramundi the biggest 94cm about 12kg. The pool construction is PVC with 2 x filters. these are standard sand filter and cartridge filter. neither of which seem to keep the algae under control. <Lots you might try to keep the algae under control... shading, adding aeration, circulation, the use for competing (for light, nutrients) vascular plants...> I am wondering what is the best option for keeping the water clear, what if any filtration system do you recommend. and what if any chemical additives do you suggest. <Not this last... too expensive, risky, undependable> Baring in mind these fish are fresh and salt water variety, but can live in either, I have chosen fresh water. A few facts about the pool. 1. it holds 25 thousand liters 2. it is constantly in the sunshine 3. it is made of PVC 4. it has 2 filters (as noted above) 5. I am happy to purchase a filter from wherever as long as it works. 6. I have heard of some Brazilian filter that keeps the water clear, but not sure on detail. I recently put in an additive (pond clear) it seems to have overdosed the fish, <Mmm, if this is the same (Weco) product we have in the U.S. it is simply "alum" (aluminum sulphate) and really only of practical use in precipitating phosphates... do you have measurable soluble phosphate? In any case, I would not use such in your setting> and subsequently they have all died, I am interested in re stocking but would dearly like to maintain a clear water environment. The whole reason for having the fish is to watch them swim around and enjoy live bait when I throw it in for food. <Understood... there are a few approaches you might employ here, including much enlarged biological filtration, ultraviolet sterilization, ozonization... but I would go the "sail boat" versus the "motor cruiser" mentality here... due to the size (25 k l) and constant sunlight issues... and not wanting you to go broke paying for such types of intervention, or be broken hearted killing off your livestock... or bald from pulling your hair out! Do read through the algae control sections posted on our site: www.WetWebMedia.com, principally under the Pond Subweb... and look into shading, live plant use, added aeration, circulation. Bob Fenner> if you can help that would be great. best email contact is thanks and regards Clayton.

Pond, filter/ration, livestock re-doing outdoor pond in Maine ... will be approx 12x16 ...3 ft. deep at middle ...will include creating wetland environment ... but, I'm wondering if I should consider creating some type of big under gravel filtration system .... also Koi and goldfish are illegal here ... big fines if you're caught ...any recommendations re live stock ...thanks much for your attention ...djk. <I would NOT build an in-pond filter here (or most anywhere it can be avoided)... Nigh to impossible to service, clean, repair... Please read through the Pond sections of our site: www.WetWebMedia.com Re the stocking issue, do ask at local garden centers, livestock fish stores and your state civil servants (fish and game) re what they DO allow and advise. It may well be that some local species will make a spectacular display... and present adventures to you in their collection. Bob Fenner>

Pond Filter Hello, <Greetings> I have a question concerning my pond filter. The pond is 250 gallon and has a pump that is adequate for that size pond. My question is, why do I have to clean the filter twice a day? <Mmmm, you tell me... is it too "dirty" otherwise? You may have too much nutrient in your source water, getting in through fertilization... fueling algal growth... maybe the foods/feeding you do have a role here...> It get so clogged up the water stops so I have to keep a careful watch on it. I have a friend who has a similar pond and she doesn't change hers nearly as often. The water in my pond is clear and it tests perfectly and the fish seem healthy. What is the problem? Thanks! Ann <It may be that the media in your filter is inappropriate... or that it has become channelized and otherwise compacted... Please take a read through the pond sections posted on WetWebMedia.com and see if what is posted there reveals the problem here. Bob Fenner>

Bird poop in Small Goldfish Pond II - 8/15/03 Thank you for answering Anthony. I will not assume it is bird droppings. The pond's life is almost 8 months. There is a small pump and sponge filter and I do water changes every couple of months. I have two goldfish, water lily and lots of water lettuce, and oxygenating plants. Am I on the right track. Marty <the sponge filter may be too small, and the water change schedule is very modest. Some pond keepers try to do at least 10% weekly. 25% monthly at least. Especially during warm weather. Best regards, Anthony>

Hello, Sabrina - Pond stuff and filter recommendation <Hi again, Patricia!> Thank you for re-assuring me about my little red creatures. I have had aquariums or ponds all of my life (retired now) and these creatures are totally new to me. I will do some more checking. I think I can send some of the creatures to a local Univ. or government agency. I'll check the web for insect larvae. I think you are right. Again, Thank you for responding...Oh, yes, I need a new Pond Filter for 2,000 to 5,000 gallons, any expert advise on a good one. Thank you, Patricia in Seattle <Well, the only filters for large ponds that I've had much experience are the Tetra Clearchoice filters. They seem to work well, but I have only small ponds. I know one of the Clearchoice filters is good for up to 2600 gallons. Any time! -Sabrina>

Pond Bubbler System Do you have or can you point me in the right direction where I might find engineering details for a bubbler system. We have a 100 X 50FT X 8FT deep pond which we want to use as the reservoir for an emergency fire pump. The information I'm after includes the CFM compressed air requirements for a certain length of hose, drilled for aeration (hole sizes), submerged to prevent freezing during our cold winter months. Most of the systems I've seen pump down to a ring main, 6FT in diameter and are used around docks having a rather small area to protect. We would like to ensure 70-80% of the entire pond remain ice free. I can size the compressor / blower once I know the air requirements. Hope you can help. <Mmm, don't know right off where to refer you to. When we (our old lake management division) used to spec. such aeration/destratifiers, we mostly oversized compressors (garden variety) for anything a few tens of feet deep (deeper we used Gast air compressors)... that would develop more than 14.7 psi per thirty two or so feet of depth and a good cfm per two holes of about 3/8 inch diameter. I do greatly favor making your own diffusers... out of PVC pipe of two inch diameter... in a "standing rectangle" arrangement... with the holes drilled in the upper bar of PVC in the area facing down (best to snap a line, maybe use a drill press to get all straight. The "standing rectangle" can be made with "tees", elbows to allow for "feet" to place cinder block on to hold down... Other diffusers always proved problematical over their service lives. Have you taken a look at Aquatic Ecosystems site? http://www.aquaticeco.com/aquatic1v1/index.icl?orderidentifier=ID1056074040150131E58 They may well have other ideas.> Regards Dave McKenna PS: Your site just gave me a great idea with my worn out swimming pool (read: soon to be pond)! <Ah, good. Bob Fenner>

Pond information wanted Dear Robert Fenner: I am a landscaper in Argentina and I would like to construct a biological swimming pond in my backyard. I knew about you by internet and have been reading all your excellent material in which I am very interested Would you be so kind of sending me full information about in-pond gravel down flow filter system or some bibliography about this subject? I would also need if it is possible some graphic picture. I thank you in advance for your time and help. Best regards, Alfredo Laplacette. <All but the graphics are pretty much archived on WWM. Any illustrations are back in San Diego/California. We're in Hawai'i now. If you have specific questions, concerns, please send them along. Bob Fenner>

Green Algae in pond I have always found valuable info on your site. Thanks for keeping it up. I have a 65 gal pond I put in my back yard about 6 months ago. It's one of those that comes in a kit from Wal-Mart with a pump a little strainer a waterfall and that's about it. I've been having green algae problems and haven't been able to fix it myself. My wife's grandmother has a concrete pond probably about the same size as our that she has had for a long time. She seems to never have had an algae problem. I guess she cleans it once a year. All she has in it for a filter is one of those boxes from Home Depot that the pump sits inside of. Seems like a pretty simple thing. Aside from doing a complete water change and scrubbing the liner don't mine, I don't know what to do. Last night I went to Wal-Mart and bought a plastic box with some poly fiber material and made a filter box to lay my pump in. I put it in last night and it has been running all night. The water still is green. I figured I'd probably have to let it run for a few days like that and then change the filter media out. <Yes, more likely a few weeks to months starting in cold weather> I tried using stuff called Algae Destroyer Liquid, but it doesn't seem to do a thing. <I would stop using this product, material... it's too toxic for your use, will kill the surrounding landscape...> As far a fish, all I got in there right now is 8" catfish. Now I think there is quite a layer of crap at the bottom of the pond but I'm not planning to stick my arms in the water right now. Too cold for Jacksonville, FL. We've had a few days of hard freezes and that pond water is cooooold. Any suggestions, ideas, comment would do nothing but help at this point. By the way, I prefer to deal with DIY things. I like the hands on training it provides. Thanks. <Please read over the pond filter sections posted on our site, starting here: http://www.wetwebmedia.com/PondSubWebIndex/pndfiltrovr.htm and going over the rest linked (in blue, at top) to give you a good grounding in the subject, your choices. Bob Fenner>

Moss (Filamentous algae in a new pond) I am new with the computer and the pond/water fall ownership. <Lots of excitement!> My son and I put in a water fall and a 1500gal. pond in the front of our house. It has nine gold fish and two bottom feeders. All seem to be doing well including the various plants. This water feature has been completed for about three months However, I have a big moss problem. This stuff is long stringy and is hanging from the water fall and is all over the pond liner and plants. My oxygenator plants look like a ball of this moss stuff. how can I get rid of it and keep it clear of this stuff? I live in Cincinnati and the pond is on the east side of the house. <Many ways to counter these pest algae problems. Please read here: http://www.wetwebmedia.com/PondSubWebIndex/pdalgcontrol.htm and consider what your possibilities are... perhaps more filtration, circulation, pH adjustment, shading... Bob Fenner>
Re: Moss (Filamentous algae in a new pond)
Sorry to bother you again. I read the article you recommended and have learned that I need some type of filter in my system. I didn't realize that a filter was necessary for control of the chemistry, I thought that the filter controlled particulates. Thanks so much for your comments!! <Yes to having a filter... and you're so correct re its impact on the overall health and appearance of the system. As you'll find, many folks build the filter for ponds first and foremost (it IS that important) and build the rest of the system, landscape around it. Take a read through the many design, construction and filter materials posted on the Pond Subweb: http://www.wetwebmedia.com/PondSubWebIndex/Pond%20Sub%20Web.htm Be chatting, Bob Fenner>

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

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V. 2 Print and eBook on Amazon

by Robert (Bob) Fenner
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