How to layer a bio-filter

[tlc]

I will be building a filter that will be about 240 gallons +/- and I have been reading the thread about adding lava rock which I found to be very useful.  Now I have a question or two about layering the bio-filter.

On the bottom of the filter you have a space for the water to enter from the pond. It then flows up and out the filter via falls or stream.
My question is, how should the layer the filter material? Bio-balls then filter pads (Matala or whatever) or the other way around?

If you were to use bio-balls, filter pads and some lava rock, all together, what would be the most efficient to have those layered?

[-Greg-]

tlc, there are other forms of media as well, for instance the "sand and gravel" filter. I built one myself and substituted crushed oyster shells (chicken grit) for the sand. Here is a good example:

http://www.koiphen.com/forums/showthread.php?t=36550

I built mine just like Kent's in the thread and have been extremely happy with the performance and the ease/lack of maintenance.

Greg

[casey]

tlc,

Ours is 300 gallon rubbermaid stock tank.  From the bottom up it has 1) a plain water space made by plastic crates cut down to about 8".  They are placed upside down to cover as much of the bottom as possible (bottom is round, crates are square), 2) Next are filter pads supported by the upside down crates (ours are white but sorry I don't know the exact density), 3) laying on the filter pads is lava rock from there all the way to the top of the water in the tank, about 3 " from the actual lip of the tank. 

In one place along the edge of the tank there is a cutout.  That cutout is where the water goes out over the fall made of flagstone.  So, the outlet (flagstone fall) is some inches below the lip of the tank and that is why the water goes out there instead of over the edge of the tank wherever it wants.

Because our filter is so large and I like plants so much, I actually took out about 3-4" of lava from the top so I could set shallow (oil pan type) pots on the top of the lava rock.  The edge of these pots are barely under the water so that I have a nice bog situation for the plants in these pots.  I grow cannas, horsetail, celery, dwarf cattails, and other bog stuff up there so you don't really see much of my filter, just nice green.  The pots are all along the inside perimeter of the filter and there is plenty of room in the middle for me to get in there to tend the plants and use my Pondvac to get any sludge the settles up there.  I try to be careful to trim around the plants to keep the roots mostly out of the lava.  It really helps the filtering if you let the roots go into the lava but it is really a pain to clean then and to get them out.  We used to put irises up there but they were so bad about jumping the pot and we had roots going all the way to the bottom of the filter, about 3'. 

This is just our way and there are tons of other good ways used by other forum members.  We don't use bio balls or filter media because I want plants up there (lots of weight) and I want to climb in there too (I wear cheap rubber mid-calf boots).  Hope this helps. 

Casey

[tlc]

Thanks Greg. I did have a look at the link that you posted That setup wouldn't work for me as I'm doing something a little different than the norm but you wouldn't have known since I didn't include the details

Casey, it does help and thanks for the long reply with lots of details I'm glad you posted about the iris going for a "walk" since I was thinking of doing that very thing. Good tip. I like the idea of being able to set the pots on top of the rock. I never thought of doing that. For me, standing on the rock might not be an option b/c of the material I will be using.

My setup will be a little different like I said above. I plan on having the filter buried with the top exposed (just like a stock tank would). The water would exit the filter into the steam that would spill into the main pond below which is not built yet either. I have quite a drop from the filter to the pond and hope it's enough. I plan on using pond liner instead of the normal stock tank that most ppl use. I have the backhoe attachment on my tractor so I can dig it myself and the pond liner doesn't cost that much compared to what a stock tank costs in my area. Plus I like the fact that I'm not stuck with one shape. That is the idea for now and since I'm a girl I do reserve the right to change my mind .

[tinkster]

tlc... yours sounds much like i did mine.  I was building on the side of a steep bank and i dug my 'skippy filters' into the bank and lined them.  I did two.. one behind the top fall drop and another for the 2nd drop.  The water upfeeds through these green floor scrubber pads  and out over the falls. 

Tink

[casey]

tlc,

Good luck.  If you have any questions specifically for me you can email me off-line.  I travel a lot and go weeks at a time without checking the forum.

Casey

[Otter]

I have the same bottom-up setup you are building, tlc, though it's an Aquascape Biofall instead of a nice big hole in the ground.  My filter box drains onto a slab of flagstone about two and half feet above the pond.  Pump is rated for 3000 gph, but my guess is that it's moving a little less than that.  Some of the falling water hits rocks there, and some hits the surface of the pond.  It makes a really wonderful sound.

I have a green, medium density matala pad, then two blue, high density pads, then bioballs.  Why these materials?  Because the pond came with them.  Though bioballs don't clog up easily like lava rock, the reason for this arrangement is that the balls are rather difficult to clean.

Will you have any mechanical filtration before the biofilter?  I highly recommend it.  The downside to a bottom up filter is that you have to take everything out to clean it.  Some claim that with a big enough biofilter you don't need to do this, and I suppose with a very large filter and a very small load that's true.  But I've read posts by a number of folks who tried to go the "Skippy" route and discovered that pond debris does not in fact turn magically to sand.  If you think about it, all that stuff is still in your water, and unless you have very few fish and no trees, it's probably not a good idea to leave it there.

Since I installed a skimmer with a filter, cleaning the biofilter has been a lot less work.  The new skimmer came with a very dense filter pad, almost like something you'd find in an aquarium filter.  This needs weekly cleaning during some parts of the year because it tends to clog up with pine needles, but easy and it's worth it because it keeps most of that out of my biofilter.  Very little debris reaches the biofilter now, and the green pad caches most of it.  If I were building this type of system from scratch, I'd have a skimmer basket, then a series of pads or screens, strictly for mechanical filtration, then the pump, and finally a big hole full of pot scrubbers.  Pot scrubbers have about three times the surface area to volume as bioballs, and are much cheaper.

I don't have enough bioballs to fill my filter, so I'm going to get scrubbers.  Because the scrubbers are so cheap and provide more surface area, I'll probably take the bioballs I have out.  Maybe I can find somewhere to hide them under the waterfall or float a few in the skimmer.

You might want to consider a horizontal filter.  Here's a good article on that and other things:
http://www.akca.org/library/filter2.htm

And if you run across them yet, wet/dry or trickle filters have extremely good performance because they provide more oxygen for both bacteria and fish.  This type of filter will freeze if you don't shut it down when the weather turns cold, though.

[tlc]

Thanks guys

My filter size will be 4x4x2 +/-. I thought I would set it up with the water coming in from the pond to the bottom like everyone says. I just wasn't real sure what to do next but now I have a better idea. I read on the forum (written by Jerry I think) about cutting up PVC to use in place of the bio-balls. I have lots of that laying around from the irrigation setup that the ppl that owned our propertly before us used. I figured I could set it up in the bandsaw and whack away. Wouldn't take that long really and I would be recycling the material instead of it going into the dump.

Frogman3 (and now Otter) brought to my attention that I should consider a pre-filter (mechanical) to my bio-filter. That sounds funny to have a filter before the filter but makes sense. Now I'm trying to come up with something for that. Always something

What I have learned so far is that the filter is very expensive to set up. Much more expensive then the pea gravel in the aqua basket that I have my little pump set into. But it is what it is and if I'm going to have a pond then I just have to deal with it. My idea is to end up with something that isn't alot of work. We are gone alot during the summer and would like the peace of mind knowing that everything is working as it should.

I see everyone talking about these cheap scrubbers but can't figure out what they are talking about. The ones I have seen haven't been that cheap so I don't know if I'm looking at the right stuff or not. Are you talking about "Scotch Bright" pads??

btw, welcome Otter

[Otter]

Thanks.  I didn't realize that was my first post here. 

Go here:
http://www.dollaritem.com/
and search for item 42834, and you'll see what we're talking about.

[Edit] But don't order from this company.  Their employees are friendly and do their best to be helpful, but the company itself seems to be extremely disorganized.

I tried to order from them back in late March, and managed to place an order after much fussing online and several phone calls.  Called back two weeks later to find that the scrubbers were backordered, and my payment info and part of the order had been lost (again).  But their rep said the scrubbers had left China the next day, and would arrive in the US in about two weeks.  Though at first it seemed very odd that she would tell me something had shipped on the following day, it is possible if you take into account the international date line.  But having received neither word nor scrubbers by late July, I canceled the order.

I'm moving toward anoxic filtration, and hence don't need scrubbers anymore, but here's another wholesaler you could try: http://www.dollardays.com/i296104-wholesale-scouring-pads.html
[/Edit]

If you sign up, you'll find you can get 5 cubic feet of scrubbers for about $75 shipped.  If you buy them at the dollar store, they're about 50% more, but you don't have to buy them by the case.  There may be even better deals out there.

BTW, how are you getting the water to the bottom of your filter?  If it was me, I'd run the pipe over the top rather than up through the bottom.  If there are no seals in your system, you don't have to worry about them leaking.

[tlc]

Otter,
If you mean, running the water line from the pump in the pond to the bio-filter up over the top and down to the the floor of the filter instead of cutting a hole in the liner and attaching some kind of fitting, then yes, that is what I thought I would do. I don't want any chance of leaks while I'm gone that might pump the pond dry. I don't think my fish or plants would be very happy with me if it did.

Thanks for the link too

[Otter]

If you mean, running the water line from the pump in the pond to the bio-filter up over the top and down to the the floor of the filter instead of cutting a hole in the liner and attaching some kind of fitting, then yes, that is what I thought I would do. I don't want any chance of leaks while I'm gone that might pump the pond dry.

Yep, that's what I meant, and having had leaks where the liner attaches to both my filter and the original skimmer, I'm all for the seal free approach.  Granted, the previous owner didn't leave any slack in the liner and overtightened the screws, and either acidic water or the oxidizer he added ate away the aluminum hardware, but I'd still go up and over wherever I could on a new build.

One clarification on the dollaritem.com pot scrubbers: the box is about 5 cubic feet.  I'm not sure how much air ships with a case of scrubbies. 

Have you seen this yet?
http://www.wernersponds.com/biofiltermedia.htm

[tlc]

Me too. I like the idea of having one less thing to worry over.

Nope, I haven't seen that one before. I was surprised at how some of the material that I thought would work well didn't have the surface areas.
Thanks for the link. That will come in handy

[Lawrence of PA]

Otter, I just checked the dollaritem web site, and they apparently have a $1500 minimum order.  So with my $57 worth of pot scrubbies, I guess I need to find another $1450 worth of stuff I don't need  .  Am I missing something, or have they changed their minimum order policy. 

Thanks for the link to wernersponds.  I'm astounded that the cheapest media has the most area per cu.ft.  That must be one the best kept secrets in the biz.

I haven't decided whether to punch a hole in my 25 gal waterfall bucket, or go over the top and down.  But this looks like the year of the cheap band-aid until I can re-do the pond, install a skimmer, bottom drain, and a working filter-falls.

I'm thinking some sort of egg-crate bottom diffuser; a couple cu ft of scrubbies; a layer of coarse mat to hold the scrubbies down, and a dishpan full of bog plants on top to keep everything else from floating and also to provide some veggie filtration.

Larry

[reddad35]

Greg that link to the filter has been read, purchased, built and is about done. I should be plugging it in tomorrow. I am excited as heck to fire it up and test the air back flow feature.  Thanks

[Otter]

Otter, I just checked the dollaritem web site, and they apparently have a $1500 minimum order.  So with my $57 worth of pot scrubbies, I guess I need to find another $1450 worth of stuff I don't need  .  Am I missing something, or have they changed their minimum order policy. 

That's only if you want free shipping.  There may be a more elegant way to get out of that, but what I did was clear everything out my cart (they suggest deleting the cart, but the link for that doesn't work).  Then go to the top of the site, search for the item number, add it to the cart again, and $57 worth of scrubbies costs aoubt $75 delivered to your door.  Works out to about 10 cents a scrubber.  Still a pretty good deal considering six for a dollar plus sales tax at the dollar store is about 17 cents for each scrubber.

Thanks for the link to wernersponds.  I'm astounded that the cheapest media has the most area per cu.ft.  That must be one the best kept secrets in the biz.

What amazes me is that after all these years none of the pond vendors are selling pot scrubbers.  Yeah, bioballs and superultramegabioceramicmaxplus cost more, but a pond site could probably sell a lot of scrubbers at the dollar store price.

I'm thinking some sort of egg-crate bottom diffuser; a couple cu ft of scrubbies; a layer of coarse mat to hold the scrubbies down, and a dishpan full of bog plants on top to keep everything else from floating and also to provide some veggie filtration.

That's the band-aid?  If you can figure out a good mechanical pre-filter, your biofilter will work a lot better and be easier to maintain.  Try to set it up so that you don't have to touch the biofilter to clean the debris out of the mechanical filter.  This will reduce stress on both you and your bacteria.

[Lawrence of PA]

What would a simple, pressurized pre-filter look like?  My pond level is at grade, so anything that comes before the waterfall would have to be pressurized.  I have a pressurized filter I bought last year.  The problem is that it needed cleaning about every other day, and despite the claims, it didn't backwash effectively.  So  I was stuck with shutting down the pump, disassembling the filter, and cleaning the mesh and foam elements every 2-3 days.  That got old fast.

The reason anything I do this year is a band-aid is that I need to redo the whole thing and try to get enough elevation to have a gravity-fed prefilter/settling chamber.

Any thoughts?

Thanks, Larry

[Otter]

Where is your pump?   If there's some sort of cage around it already, maybe you could find a bag to put over that.  If it's just sitting in the pond, maybe you could build a skimmer of some sort around it.  Maybe make a couple J shapes out of PVC and join them to form a frame for a screen with a catch basket at the bottom.  If you surround your pump on three sides with large screens, you could go to France for a month without worrying about the pump cavitating. Or if you've already got a skimmer, maybe you can fit a filter in somewhere.

A pressurized mechanical filter doesn't seem worth the effort because you'd have to crack it open frequently to empty it.  If the filter must be outside the pond, though, I suppose you could pump the water above the level of the waterfall, and make a downflow mechanical filter - just a big tub to hold some cheap screens or filter pads with a pipe connecting the bottom to the bottom of your upflow biofilter.

[reddad35]

I just built the filter system listed on the first reply. (Sand Gravel, Air) It seems to be working great. I will let you know if if cleans up the water. No leaks, thats always a plus. Total cost 89 bucks. .......... easily hid too

[frloplady]

Thanks.  I didn't realize that was my first post here. 

Go here:
http://www.dollaritem.com/
and search for item 42834, and you'll see what we're talking about.

If you sign up, you'll find you can get 5 cubic feet of scrubbers for about $75 shipped.  If you buy them at the dollar store, they're about 50% more, but you don't have to buy them by the case.  There may be even better deals out there.

BTW, how are you getting the water to the bottom of your filter?  If it was me, I'd run the pipe over the top rather than up through the bottom.  If there are no seals in your system, you don't have to worry about them leaking.

I bought shower back scrubbies..they are about 3" in diameter and 10" long.  Probably not every $ store has the same stuff, but they worked great for me.

Lava rock works, even works well..but it can be a royal pita.

I lOVE my sand/gravel filters.  I have 2 50 gallon barrels I run in parallel of a settlement chamber from one of my bottom drains.  Helps keep a 13,000 gallon pond clean

[Johns]

For new ponders:  Just a thought from someone who has been screwing around with fish ponds for over 30 years:  There may be somehting worse than lava rock for biofilter media, but I have not as yet found it.  The available surface is limited, the pores clog easily, and the weight of the clogged media is enormous.  Scrubbies, bird netting or any commercial media are better.  What do I use?  I cut 3/4" pvc pipe into 1 inch sections and bag them in mesh nylon bags for easy handling.  They never wear out, never clog, have a huge surface area, and are easily cleaned.  Everyone has their favorite, but it's a safe bet that anyone ponding more than 10 years will not include lava rock as their favorite.  Just my opinion, worth exactly what you paid for it.

[frloplady]

Johns the only way to use lava is with a blower under it to help clean it.  But agree it was my "favorite" when I started, but certainly there are much better media (even cheap DIY stuff) that work as well or even better and are much easier to clean.

Any filter that has to be torn apart to clean (I have 3..  ) is a pain in the behind.  Better a design that has a drain in the bottom and can be rinsed from top down.

[reptilegrrl]

The media in my biofilter is floor scrubbing pads from a janitorial supply house.  I have a swirling chamber underneath a grid supporting the pads.  There is really no need to layer different types of media.  I looked into a sand-and-rock type filter before I built this one, but I read a lot about lava rocks getting clogged up and becoming useless.  I wouldn't use bioballs myself, they are expensive and don't have great reviews. 

I find that about once a year I need to clean the pads because they get a lot of scummy stuff built up on them and it blocks water flow through the pads- the flow gets channelized so the water is not as clean. 

[reptilegrrl]

Regarding a prefilter, I built my own.  I bought a little plastic storage box at Big Lots, the kind with a lid that snaps loosely on.  I used a drill to make lots of little holes in it.  Then I made a bigger hole for the hose to go in the side.  The pump goes inside this box, wrapped in aquarium filtration media, the kind that is bonded blue and white batting.  The pump pulls water into the box through the holes and then through the batting.

Before adding the prefilter I had to clean the skippy every 6 months or so and it would be very filthy.  Now I clean the skippy every 12-18 months, because algae still builds up in there and the water flow becomes channelized.

The prefilter needs to be cleaned maybe every 3-4 months; I can tell when because flow gets very slow.  I just unplug the pump and pull everything out, and use the water hose to clean all the crud off of the batting.  I don't worry about preserving bacteria in the prefilter, so I just hose it down really well then put it all back together.  It takes about 10 minutes really.

I also forgot to say that I have a grid on top of the media in my skippy, there's a handy ridge it sits on.  I set plants on top of that.  I also have moneywort growing directly in the skippy itself, it trails down the sides and looks very pretty.

[frloplady]

The media in my biofilter is floor scrubbing pads from a janitorial supply house.  I have a swirling chamber underneath a grid supporting the pads.  There is really no need to layer different types of media.  I looked into a sand-and-rock type filter before I built this one, but I read a lot about lava rocks getting clogged up and becoming useless.  I wouldn't use bioballs myself, they are expensive and don't have great reviews. 

I find that about once a year I need to clean the pads because they get a lot of scummy stuff built up on them and it blocks water flow through the pads- the flow gets channelized so the water is not as clean. 

the "sand-and-rock" filters that I have do not use lava rock, but rock that can be found at any hardware or landscape supply type place.  They work well as the mimic nature (water through ground type material) but are made that they are easily cleaned as well.  The rock is not porous like lava rock so cannot harbor gunk within them.  They are a great filter for getting fines out of the water (that real fine stuff you see but cannot filter out easily)