Hi,

I want to change my filter media and was thinking about using drinking
straws and was curious as to what people thought. Characteristics of
good filter media a

1) High surface area per volume.

Assuming 12" long straws that are about 1/4" in diameter it takes about
16/in^2 * 144 in^2/ft^2 (=2304 straws) to fill 1 cubic foot. Each straw
has a surface area of 12" * 2 pi r in^2 on both the inside and outside
(=9.4 in^2). Since the straws are against each other say 25% of the
outside surface is lost, so the available surface area of each straw is
1.75 * 9.4 in^2 = 16.5 in^2. This * 2300 straws/ft^3 = 38000 in^2 = 263
ft^2/ft^3 (surface/volume). This is pretty good compared to something
like Springflow which appears to be between 60 and 120 ft^2/ft^3 space,
350 ft^2/ft^3 for lava rock, and 120-250 ft^2/ft^3 for open cell foam.

2) Displaces little water per volume.

Straws don't take much room. Rocks and pea gravel do.

3) Doesn't plug easily.

The inside of a straw can't plug. Possibly the outside could between
the straws but even that is nowhere close to what happens in lava rock.
I've been having problems with pluged filters (lots of algae) and I need
to have something that will go for a week with no problems at all. I
have pea gravel now and I'm having problems keeping the prefilter clean
so the pea gravel doesn't plug.

4) Light weight, easy to work with.

Straws are light. In a filter with straight walls it shouldn't be too
hard to keep them in place.

5) Cheap.

I went to a restaurant supply place on the net and found a case (25000
straws) of 7.75" straws for $42. That would mostly fill my 100 gallon
stock tank.

What do you think?

I am by no means an expert on this topic, but my first impression is that
the surface of the straws is too smooth. Don't we need something a little
porous or at least with some texture?
Sue

"Matt Rosing" wrote in message
...
Hi,

I want to change my filter media and was thinking about using drinking
straws and was curious as to what people thought. Characteristics of
good filter media a

1) High surface area per volume.

Assuming 12" long straws that are about 1/4" in diameter it takes about
16/in^2 * 144 in^2/ft^2 (=2304 straws) to fill 1 cubic foot. Each straw
has a surface area of 12" * 2 pi r in^2 on both the inside and outside
(=9.4 in^2). Since the straws are against each other say 25% of the
outside surface is lost, so the available surface area of each straw is
1.75 * 9.4 in^2 = 16.5 in^2. This * 2300 straws/ft^3 = 38000 in^2 = 263
ft^2/ft^3 (surface/volume). This is pretty good compared to something
like Springflow which appears to be between 60 and 120 ft^2/ft^3 space,
350 ft^2/ft^3 for lava rock, and 120-250 ft^2/ft^3 for open cell foam.

2) Displaces little water per volume.

Straws don't take much room. Rocks and pea gravel do.

3) Doesn't plug easily.

The inside of a straw can't plug. Possibly the outside could between
the straws but even that is nowhere close to what happens in lava rock.
I've been having problems with pluged filters (lots of algae) and I need
to have something that will go for a week with no problems at all. I
have pea gravel now and I'm having problems keeping the prefilter clean
so the pea gravel doesn't plug.

4) Light weight, easy to work with.

Straws are light. In a filter with straight walls it shouldn't be too
hard to keep them in place.

5) Cheap.

I went to a restaurant supply place on the net and found a case (25000
straws) of 7.75" straws for $42. That would mostly fill my 100 gallon
stock tank.

What do you think?

If the straws are lined up in such a way that the water goes through them,
then you have the internal surface area that you calculated. If they are
put in in such a way that the water does not flow through, then, I think,
the area within the straw would tend to go anaerobic and would serve no
purpose. The Aquaultraviolet tank filter, similar to the bead filters, uses
a hollow media, but it is short chopped pieces so they won't have enough
length to go anaerobic. Find a glue them together, or rubberband them
together and they would be like the pvc pipe, which builds a nice biofilm on
the inside surface.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Matt Rosing" wrote in message
...
Hi,

I want to change my filter media and was thinking about using drinking
straws and was curious as to what people thought. Characteristics of
good filter media a

1) High surface area per volume.

Assuming 12" long straws that are about 1/4" in diameter it takes about
16/in^2 * 144 in^2/ft^2 (=2304 straws) to fill 1 cubic foot. Each straw
has a surface area of 12" * 2 pi r in^2 on both the inside and outside
(=9.4 in^2). Since the straws are against each other say 25% of the
outside surface is lost, so the available surface area of each straw is
1.75 * 9.4 in^2 = 16.5 in^2. This * 2300 straws/ft^3 = 38000 in^2 = 263
ft^2/ft^3 (surface/volume). This is pretty good compared to something
like Springflow which appears to be between 60 and 120 ft^2/ft^3 space,
350 ft^2/ft^3 for lava rock, and 120-250 ft^2/ft^3 for open cell foam.

2) Displaces little water per volume.

Straws don't take much room. Rocks and pea gravel do.

3) Doesn't plug easily.

The inside of a straw can't plug. Possibly the outside could between
the straws but even that is nowhere close to what happens in lava rock.
I've been having problems with pluged filters (lots of algae) and I need
to have something that will go for a week with no problems at all. I
have pea gravel now and I'm having problems keeping the prefilter clean
so the pea gravel doesn't plug.

4) Light weight, easy to work with.

Straws are light. In a filter with straight walls it shouldn't be too
hard to keep them in place.

5) Cheap.

I went to a restaurant supply place on the net and found a case (25000
straws) of 7.75" straws for $42. That would mostly fill my 100 gallon
stock tank.

What do you think?

The math on the surface area of a straw seems correct. However you need to
remember straws are really tiny pipes, even when under pressure, the flow
rate of water through a straw is horrible. The water is much more likely to
go around the straws, compared to the water that will flow through the
straws.

I suppose that if you placed the straws vertically, and forced the water to
travel down a bed of straws, it would work. But if they were laid
horizontally, and the water just flowed around in a stock tank, very little
would actually flow through the straws.

Sameer


"Matt Rosing" wrote in message
...
Hi,

I want to change my filter media and was thinking about using drinking
straws and was curious as to what people thought. Characteristics of
good filter media a

1) High surface area per volume.

Assuming 12" long straws that are about 1/4" in diameter it takes about
16/in^2 * 144 in^2/ft^2 (=2304 straws) to fill 1 cubic foot. Each straw
has a surface area of 12" * 2 pi r in^2 on both the inside and outside
(=9.4 in^2). Since the straws are against each other say 25% of the
outside surface is lost, so the available surface area of each straw is
1.75 * 9.4 in^2 = 16.5 in^2. This * 2300 straws/ft^3 = 38000 in^2 = 263
ft^2/ft^3 (surface/volume). This is pretty good compared to something
like Springflow which appears to be between 60 and 120 ft^2/ft^3 space,
350 ft^2/ft^3 for lava rock, and 120-250 ft^2/ft^3 for open cell foam.

2) Displaces little water per volume.

Straws don't take much room. Rocks and pea gravel do.

3) Doesn't plug easily.

The inside of a straw can't plug. Possibly the outside could between
the straws but even that is nowhere close to what happens in lava rock.
I've been having problems with pluged filters (lots of algae) and I need
to have something that will go for a week with no problems at all. I
have pea gravel now and I'm having problems keeping the prefilter clean
so the pea gravel doesn't plug.

4) Light weight, easy to work with.

Straws are light. In a filter with straight walls it shouldn't be too
hard to keep them in place.

5) Cheap.

I went to a restaurant supply place on the net and found a case (25000
straws) of 7.75" straws for $42. That would mostly fill my 100 gallon
stock tank.

What do you think?

Matt Rosing writes:

I want to change my filter media and was thinking about using drinking
straws and was curious as to what people thought.

When I heard about this years ago, the person was cutting the straws
to an inch or two with a big paper cutter.

FWIW I use plastic roof gutter screening in my bio filter.

I am by no means an expert on this topic, but my first impression is that
the surface of the straws is too smooth. Don't we need something a little
porous or at least with some texture?
Sue


The crevices in my bio balls are smooth so I don't think it really matters.

snip The Aquaultraviolet tank filter, similar to the bead filters, uses
a hollow media, but it is short chopped pieces so they won't have enough
length to go anaerobic. Find a glue them together, or rubberband them
together and they would be like the pvc pipe, which builds a nice biofilm on
the inside surface.
--
RichToyBox


Couldn't he just cut the straws into smaller pieces?

GrampysGurl wrote:

snip The Aquaultraviolet tank filter, similar to the bead filters, uses
a hollow media, but it is short chopped pieces so they won't have enough
length to go anaerobic. Find a glue them together, or rubberband them
together and they would be like the pvc pipe, which builds a nice biofilm on
the inside surface.
--
RichToyBox




Couldn't he just cut the straws into smaller pieces?



25000 straws? Even with a paper cutter that might take a while But I
was thinking if they're left long then it's probably easier to line them
up with the water flow so there aren't dead spots. I suppose if they
were cut down to about 3/8" it wouldn't make a difference. But that's
around 1/2 million pieces. Then I just need to make a widget that cuts
straws. DIY heaven.

Thanks for the feedback.

I was thinking of putting the straws in vertically from wall to wall so
the water can't go around. I'd hold them off the bottom using light
diffusers and plastic window screen fabric. If the straws float I'd put
the same thing on top. My filter runs top down but because of the piping
the tank stays full of water, so I'd just pore the water in the top. I
was worried about how to distribute the water (so it all doesn't go
through just a few straws) but the fact that there's resistance to water
going through straws would help distribute it.

I'll go buy a box of straws and try this out in my sink.

Your point about water resistance is why I'm looking into this in the
first place. What I have now is a bunch of bean bags made from screening
material and either pea gravel or plastic beads (same as beenie baby
beads but I have 100 lbs). It's really easy to work with so that part is
good. I have them stacked up in a wall and made a horizontal flow
filter. Even with a prefilter of nylon batting the water doesn't flow
through very well. There's probably a 5-6" difference in water level
between the input and the output. I've looked at the bags and they don't
seem to be plugged so I don't know what's going on. I do have a pond
full of green algae (soup style) but I don't see any gunk in the bean
bags. What I'm afraid of is the bean bags provide enough drag on the
water that most of the water is going between the bags. I figure straws
would have much less resistance.

Matt


Snooze wrote:

The math on the surface area of a straw seems correct. However you need to
remember straws are really tiny pipes, even when under pressure, the flow
rate of water through a straw is horrible. The water is much more likely to
go around the straws, compared to the water that will flow through the
straws.

I suppose that if you placed the straws vertically, and forced the water to
travel down a bed of straws, it would work. But if they were laid
horizontally, and the water just flowed around in a stock tank, very little
would actually flow through the straws.

Sameer

GrampysGurl wrote:

snip The Aquaultraviolet tank filter, similar to the bead filters, uses
a hollow media, but it is short chopped pieces so they won't have enough
length to go anaerobic. Find a glue them together, or rubberband them
together and they would be like the pvc pipe, which builds a nice biofilm
on
the inside surface.
--
RichToyBox




Couldn't he just cut the straws into smaller pieces?



25000 straws? Even with a paper cutter that might take a while But I
was thinking if they're left long then it's probably easier to line them
up with the water flow so there aren't dead spots. I suppose if they
were cut down to about 3/8" it wouldn't make a difference. But that's
around 1/2 million pieces. Then I just need to make a widget that cuts
straws. DIY heaven.








Heck, everyone needs a hobby, if it keeps ya busy why not lol lol lol.

Hi Matt,
I found the following at this website which I was directed
to by the fine folks in this newsgroup:

http://www.wavepumps.com/state_of_the_art_filters.htm

"Hollow Media
A newer development is hollow media. If you took a miniature plastic "hollow
drinking straw", and formed internal walls inside it, you would not only
have the external surface area, but also an internal surface area. They are
5 mm in diameter and vary in length from ¼" to ½".

This media has 750 square feet of surface area per cubic foot. So a filter
with 2 cubic feet of media will have 1,500 square feet of surface area, and
will be able to process 150 grams or 1/3 pound of food per day. This is over
4 times more efficient than bead filters, but 1/10th of the sand filter's
surface area.

Its cost when used in a filter is about $0.75 per square foot of surface
area or more than 3x sand.

The first disadvantage of this new media is the difficulty of manufacturing
it. The units are obviously very small and have a very complicated design,
which makes them very expensive at about $200/ cu ft.

The second disadvantage is they are made of styrene. You can test this by
putting some media in water. If it sinks it is most likely styrene. Another
test is to burn it since styrene burns with a black sooty smoke. Styrene
oxide as a contaminant of styrene is known to be very toxic to bacteria,
which would be a disaster to bacterial colonies for nitrification."


Hope this is helpful,
Mark

That's interesting. Thanks Mark.

Drinking straws are not styrene. They float, for one. I bought 160
straws to play with and one thing I did notice is that they pack in a
hex pattern and I'm not sure much water will flow around the outside of
each straw. But at the same time more straws will pack into a square
inch so maybe the 260 sq ft of area per cubic foot of space is a bit
high. Not as good at 750 sq ft per cubic foot but the good news is the
price is closer to $4-$5 per cubic foot of straws.

I'll buy the straws and try it out. My kids will have a blast with the
straws. My wife might not


Matt

Mark T. wrote:

Hi Matt,
I found the following at this website which I was directed
to by the fine folks in this newsgroup:

http://www.wavepumps.com/state_of_the_art_filters.htm

"Hollow Media
A newer development is hollow media. If you took a miniature plastic "hollow
drinking straw", and formed internal walls inside it, you would not only
have the external surface area, but also an internal surface area. They are
5 mm in diameter and vary in length from ¼" to ½".

This media has 750 square feet of surface area per cubic foot. So a filter
with 2 cubic feet of media will have 1,500 square feet of surface area, and
will be able to process 150 grams or 1/3 pound of food per day. This is over
4 times more efficient than bead filters, but 1/10th of the sand filter's
surface area.

Its cost when used in a filter is about $0.75 per square foot of surface
area or more than 3x sand.

The first disadvantage of this new media is the difficulty of manufacturing
it. The units are obviously very small and have a very complicated design,
which makes them very expensive at about $200/ cu ft.

The second disadvantage is they are made of styrene. You can test this by
putting some media in water. If it sinks it is most likely styrene. Another
test is to burn it since styrene burns with a black sooty smoke. Styrene
oxide as a contaminant of styrene is known to be very toxic to bacteria,
which would be a disaster to bacterial colonies for nitrification."


Hope this is helpful,
Mark

I think it is a great idea!

Light!(Will not hold water)
Easy to inspect! (Shine a light to look for blockage)
Easy to clean! (A little moderate pond water pressure from a hose would push
any crud through to the bottom)
All crud will fall directly to the bottom! (bottom drain in filter?)

Might have to gasket between the straws and the container to prevent short
circuit.

Lets see you do the math to calculate the friction loss!

Tom

"Matt Rosing" wrote in message
...
That's interesting. Thanks Mark.

Drinking straws are not styrene. They float, for one. I bought 160
straws to play with and one thing I did notice is that they pack in a
hex pattern and I'm not sure much water will flow around the outside of
each straw. But at the same time more straws will pack into a square
inch so maybe the 260 sq ft of area per cubic foot of space is a bit
high. Not as good at 750 sq ft per cubic foot but the good news is the
price is closer to $4-$5 per cubic foot of straws.

I'll buy the straws and try it out. My kids will have a blast with the
straws. My wife might not


Matt

Mark T. wrote:

Hi Matt,
I found the following at this website which I was directed
to by the fine folks in this newsgroup:

http://www.wavepumps.com/state_of_the_art_filters.htm

"Hollow Media
A newer development is hollow media. If you took a miniature plastic
"hollow
drinking straw", and formed internal walls inside it, you would not only
have the external surface area, but also an internal surface area. They
are
5 mm in diameter and vary in length from ¼" to ½".

This media has 750 square feet of surface area per cubic foot. So a
filter
with 2 cubic feet of media will have 1,500 square feet of surface area,
and
will be able to process 150 grams or 1/3 pound of food per day. This is
over
4 times more efficient than bead filters, but 1/10th of the sand filter's
surface area.

Its cost when used in a filter is about $0.75 per square foot of surface
area or more than 3x sand.

The first disadvantage of this new media is the difficulty of
manufacturing
it. The units are obviously very small and have a very complicated
design,
which makes them very expensive at about $200/ cu ft.

The second disadvantage is they are made of styrene. You can test this by
putting some media in water. If it sinks it is most likely styrene.
Another
test is to burn it since styrene burns with a black sooty smoke. Styrene
oxide as a contaminant of styrene is known to be very toxic to bacteria,
which would be a disaster to bacterial colonies for nitrification."


Hope this is helpful,
Mark

Thomas Ball wrote:
I think it is a great idea!

Light!(Will not hold water)
Easy to inspect! (Shine a light to look for blockage)
Easy to clean! (A little moderate pond water pressure from a hose would push
any crud through to the bottom)
All crud will fall directly to the bottom! (bottom drain in filter?)

Might have to gasket between the straws and the container to prevent short
circuit.

Tom, what do you mean by "gasket between the straws and the container?"

One summer we used plastic forks as our filter media. It worked well,
but they turned out to be heavier than I had expected. Will be
interested in any feedback on using straws if anyone tries it.
--
zookeeper

One summer we used plastic forks as our filter media. It worked well,
but they turned out to be heavier than I had expected.

Hey, good idea!

What do you use now?