Any ideas for a dcent DIY Skimmer

[Zephrant]

Yep, that sounds good to me. I believe that there is a sweet spot though- Too short and you get too wet of foam, too tall and you just have a tall tube with crud on the walls. And I think it depends greatly on the air volume too. .5 CFM though a 3.5" tube does not need the height that 2 CFM needs, to have the same dwell time in the neck.

In my own experience, somewhere around 6-8" is the minimum height (on a 6" main column), depending on air flow.

I know that Kevinpo added a 12" main chamber extension to his skimmer, and he is very happy with the extra height. That was adding a 6" dia. chamber on to a 6" dia. skimmer, so not extending the neck, but it has a similar effect if you don't change the internal water level.

Adding 12" of a 6" tube is the same volume as adding 37" of a 3.5" tube.

Thanks for the discussion all- Not only do I learn from you guys, I learn from myself when I am forced to reconsider design decisions.

The taper is an interesting idea, but tough to manufacture. So far I'm not convinced that it offers enough of a benefit to offset the multi-thousand dollar cost of a custom mold to have one made. (And I'd need one for each tube size, too).

Mike- can you post part numbers for your pump and air stones? I'd like to put together my own test platform that follows your ideas. I'd be thrilled if I could offer a product at half the cost of a Beckett skimmer, that still worked well.

Zeph

 

[DonW]

Here is what I was thinking. Just a thought no dimensions yet.

Don

 

[dwall174]

Not meaning or trying to hijack your thread here Collin! But I have a quick question for mike!

The stones are now made of all sorts of different components and can live indefinately if cleaned. The new stones produce finner bubbles then did the wood ones and can be cleaned to new in minutes with a muratic acid wash.

I've been planing a 5’ tall x 6” dia. skimmer (Snailman Style) that would be gravity fed from the main tank & only a linear style air pump as the air source! I have looked at the air diffusers that Aquatic Eco Systems has & was wondering which ones to try! The regular Sweetwater or the Generation II? Also is it better to have several smaller stones or one large one? Thanks!

 

[mojoreef]

What would you assume the most effiecient neck height to be in this regard Mike?

Tough call, if you have enough lift from the air it wouldnt matter, but you have to put a few thigs into concideration, such as the size of the place it is going to go and so on. Personally I would like to see at least 12 inches.

I assume at a point the bubbles would become too dry and fall back into the main chamber.....until eventually the top layer of the protein skimmer would resemble the collection cup!!

Now Collin thats where the wet neck comes into play!!!!!!, the thin fil of water keeps that interface clean as a whistle and slick.


Mike

 

[mojoreef]

Yep, that sounds good to me. I believe that there is a sweet spot though- Too short and you get too wet of foam, too tall and you just have a tall tube with crud on the walls. And I think it depends greatly on the air volume too. .5 CFM though a 3.5" tube does not need the height that 2 CFM needs, to have the same dwell time in the neck.

I dont know Brent. I dont like the thought of being restricted by the tube, think wet neck!!!! lol make that neck wet and you are not restricted by the crud sticking?? You lost me on the cfm/dweel time/tube thing?? The mixing chamber would be the box,just like on your existing skimmer (gee you know now that the mind is running here you could make the box actually be a chamber of one of you sumps???LOL) ok back, the tube is all for foam.

Mike- can you post part numbers for your pump and air stones? I'd like to put together my own test platform that follows your ideas. I'd be thrilled if I could offer a product at half the cost of a Beckett skimmer, that still worked well.

Ok now Brent I went way over kill, but here is what I have. I am running the Whitewater LT28 it pushes 5 cfm at 7.5 psi, way to much, Would say the LT 24 would have done the trick at 3.5 cfm and 6 psi. For the stones I ran the Sweet water ultra fine pore diffusors (AS300) they are 12 inches long and have a 1/2 threaded cpvc end. They have a max pore size of 80 microns and will only retain particules larger then that, so make sure you put a air filter that holds out those sizes. Brent it looks like I may have to make a roadtrip out thier and lay with you for a bit, maybe raid kevins tank and get some of my old clipping back again to, lol

Mike

 

[mojoreef]

Sorry Dwall I missed your post. Look up the diffusors I listed,thse are the ones that are the finest for bubbles. I would say go multiple smalle ones over one big one.

Couple things here folks, Do not match the pump cfm to the diffusor, thats what I did and I can tell you with all certainty that it is way to much bubbles. In my case it took two gallons of water and turned it into 5 feet of foam trying to drill a hole in my ceiling. It made the water way to violent also, I was shocked by that.
Second thing is I am only going by a friends word (who is a tech rep for an aquaculture set up/equipment company) as to how long before they get clooged and need to be cleaned, now this guy has forgoten more about equipment then we all probibly know but it is something I have not seen for my own eyes yet.

Mike

 

[DonW]

Mike,
Just move it outside and add on another level.
Call it yard art.

Don

 

[coolcol]

Hi ''dwall174'' No probs on hijacking the thread the more the merrier!!

Ive just been looking at the standard Sweetwater Medium Pore Air Diffuser you mentioned and my guess is to go for this one....easy on the air pressure requirements and easy to clean and they are very resistant to clogging i presume you wouldnt need to clean that often anyway....the info is they only need to be cleaned once in a YEAR!!...and some customers are still using the same airstones after 12 years!!...Wow!!(I see what you mean now MIke when you said things have moved on since wooden diffusers, those things never lasted more than a month or two!).....

On the Snailman type skimmer ...they dont come much simpler and more basic than this....but given the sizeof skimmer you propose i imagine its going to be very effiecient!!
One small point Most skimmers use gravity fed returns .....just makes life more simple just make sure your skimmer return outlet exceeds the tank level water easy!......i would have thought its easier to feed a skimmer and let it gravity return rather than gravity fed.....and worry about the return! once again forgive me if am wrong on this.

Do you plan on using pvc pipe aswell?....i dont like the idea of an opaque skimer.....call me old fashioned but its nice to see the thing working! and you can easily see faults or and obvious improvements etc......still its an easy option and it works..( i just wonder if you could cut some clear windows in the pvc pipe as viewing maintainance windows?)

Mike...5 Cubic feet of air a min......wow....you must a lot of foam!

 

[mojoreef]

Well dammit I forgot to turn the wet neck back on LOL SO thier is a bit of crud in the tube, but here is the look at the unit.

First pic is of the airstones in the skimmer box,notice the water line, six inches below the top of the box

Now a pic of the base where the box and first tube meet.

Now this pic is of the top of the first riser tube so about 3 1/2 feet up

Mike

 

[mojoreef]

Ok here are the bubbles in the neck which is two feet tall

And the the cup which is a foot tall and 10 inches round

And then the whole unit

Collin I would go with the fine pore, remember its all about the bubble size


Mike

 

[coolcol]

yeh of course your righ Mike......anyone used clear Polystyrene sheets to make a skimmer.....they ar erealy cheap in th uk and i reckon a 4ftx4ft at 4mm thick would make a great skimmer......The Polystyrene cement used to stick sheets together works similar to the solvent used on acrylic sheets...

Anyone used Polystyrene sheets befor?.......do you reckon they can be used in aquarium environments?...............I can only find acrylc sheets upto 2mm thick, not much use a skimmer.

 

[big t]

Hey isn't polystyrene another name for styrafoam?

 

[DonW]

I think your better off making a bucket/drum skimmer if acrylic is out of the question.

Don

 

[mojoreef]

http://www.gilbertcurryindustrialplastics.com/EP/perspex.htm

http://www.acrylics.org/

http://www.hitechprofiles.com/products/default.asp

http://www.key2plastics.com/plastics/frameset.htm

Hope it helps


Mike

 

[ldrhawke]

..........
All i wanted to know was how far down my 4ft tube could i place a pinwheel pump without loosing the venturi suction?......the further down the better to give the bubbles more contact time.
...........

Sorry for getting in late....just saw this thread. Like Majoreef I'm just finishing up a new, or should I say modified skimmer mor along the line of your thinking. I am using a SEDRA 900 (pinwheel) pump with the supplied ejector. The skimmer is 42" high and the pump inlet is about 6" off the bottom. It pull plenty of air...foam production is not an issue. I have to throttle back the airflow.

Misconception about ejectors.....it doesn't make any difference how high or low the skimmer is. An ejector performace is based on water velocity across it. It could see 50 foot of head, 50 foot tall skimmer, and still work fine, as long as the velocity across venturi is adequate and the venturi is a good design. Of couse you will need a 50 foot air tube keep water from flowing out when the pumps shuts down. This is assuming you have an efficient venturi that can pull a good vacuum.

I imagine people have come to the false conclusion that ejector(venturi) do not work on tall skimmers because of improper pump selection to start.

A quick short course on centrifugal pumps (from my 30 years in engineering design and application): When sizing and selection a centrifugal pump you calculate what the total discharge head it will see. A pinwheel pump is still a centrifugal pump...very inefficient flow, but nearly the same head because it has the same diameter impellor.

The total dynamic head (TDH) include both friction head and static head. The total static head is based on the combined suction and discharge head ( liquid level). Since our skimmer pump sees the same head on both the out let and inlet....static head is virtually zero. The only head the pump sees is the friction loss in the inlet and outlet. With a large inlet and out let piping that is near zero. Then only loss you have left is dynamic pressure drop across the venturi.

An analogy: if you put a fan inside a pressure vessel and increased the pressure to 50 psig......would it slow down? Would the fan require more energy. In the case of a fan in air...maybe a very very little, because the air compresses and becomes more dense. In the case of liquid no.

(The air induced air flow does affect the piump perfomance, it reduces total flow rates and reduces power requirements since the entrained air in the water reduces it SG. Energy required is directly proportional to SG of the liquid pumped. Also the pinwheel reduces performance and flow rate, but again it doesn't change the fact that the static head on the suction and discharge remain the same.)


With my set up the pump produces maximum of 17 foot of head, or about 14' at 3 gpm. A centrifugal pump always remains some place on its curve. The ejector requires about 3 to 4 gpm to pull air properly.

 

[dwall174]

Hi ''dwall174'' No probs on hijacking the thread the more the merrier!!

Well then I will toss my ideas into the pit!
My tank is built into a wall (well almost) still needs some finish carpentry work! And I have been thinking of getting a larger tank before I finish everything off! Anyway I have a lot of room behind the tanks so I could go as high as 72" with the skimmer. I would like to go with acrylic if I can find some around here that’s not too expensive :shock:
I originally wanted to run the skimmer’s drain into the pre-filter tank, But after seeing mikes foam I think I better keep my min. water level lower & drain into the sump?
Here’s an old pic of my plumbing, It’s changed a little but not much. I don’t have a digital camera yet (hopefully soon) so until then I use my brothers & update my pic’s every several months.

 

[ldrhawke]

..........
All i wanted to know was how far down my 4ft tube could i place a pinwheel pump without loosing the venturi suction?......the further down the better to give the bubbles more contact time.
...........

.......................

With my set up the pump produces maximum of 17 foot of head, or about 14' at 3 gpm. A centrifugal pump always remains some place on its curve. The ejector requires about 3 to 4 gpm to pull air properly.

Added Note: My comments are based on using a pinwheel pump for a closed loop skimmer. If the pinwheel is also the feed pumps....it won't work very well for tall skimmers. It it too inefficient a pump and cannot over come the static head.

 

[Zephrant]

..........
I imagine people have come to the false conclusion that ejector(venturi) do not work on tall skimmers because of improper pump selection to start. QUOTE]

Ldrhawke- I guess I disagree here. Consider the venturi as a device with three ports: water in, water out and air in. The air in is a function of the venturi design, but also depends on the water pressure seen at the water in and water out port.

For example, consider a venturi that can pull 1CFM at 1000gph at atmospheric pressure (14psi at sea level). Put that same venturi under 10 feet of water, and it sees 5psi more water pressure at two of the three orifices. The venturi now is only running at an effective 9psi difference at the air input, and will not run as well.

It is very easy to test- Take a venturi power-head and run it on the surface of a 24" tank, then at the bottom. Even without an air flow meter the difference is easy to tell.

Zeph

 

[ldrhawke]

..........
I imagine people have come to the false conclusion that ejector(venturi) do not work on tall skimmers because of improper pump selection to start. QUOTE]

Ldrhawke- I guess I disagree here. Consider the venturi as a device with three ports: water in, water out and air in. The air in is a function of the venturi design, but also depends on the water pressure seen at the water in and water out port.

For example, consider a venturi that can pull 1CFM at 1000gph at atmospheric pressure (14psi at sea level). Put that same venturi under 10 feet of water, and it sees 5psi more water pressure at two of the three orifices. The venturi now is only running at an effective 9psi difference at the air input, and will not run as well.

It is very easy to test- Take a venturi power-head and run it on the surface of a 24" tank, then at the bottom. Even without an air flow meter the difference is easy to tell.

Zeph

Don't disagree, but what we are talking about is skimmers, only two to six feet high. The slight change in performance can be easily compensated for by selecting a pump that develops slightly more head pressure and increases the velocity through the venturi. My point is that there is basis fore not using an pinwheel pump on a skimmer because it is four or five tall.

It is like saying you can't use an airpump because of the additional pressure on the bottom of a taller skimmer reduces the air flow. Just size and select it properly. I am not saying it may not require a little more power. my skimmer is almost 4' tall and I am throttling back on the air flow on my venturi. It could probably handle a skimmer two or three feet taller.

 

[Zephrant]

Okay- I can agree there. However I'm not convinced that the venturi on a needle wheel has a high enough performance to work when buried under 4' of water.

I've read that one manufacturer moved their Eheim pumps up higher on the large skimmers specifically due to the poor air draw when they were low. I've done my own testing and seen the same effect.

I agree that it would not be very noticeable when running a good venturi on a larger (non needle-wheel) pump.

Mike- Which venturi were you using again? Did you measure a difference in air input when you changed between 6" and 2' of water in your skimmer?

Zeph