Questions About Building a CC Skimmer

[golfsuper]

Guys,

I thought I was one of the few remaining CC users. I guess I'm not alone after all. I always think of trying a venturi or other style, but my CC skimmer is just too reliable. I'm one toying with the idea of reduced skimming, so if I lose efficiency with a CC, so be it. The operative phrase you guys are all dancing around it "contact time." BTW liquid, I might happen to have a juicy 5' section of 4" acrylic in the shop that I could let go of. I know my wife would gladly pay the shipping to get it out of her way. HeHe.

golfsuper

 

[pacmans]

Hi snailman and anyone who read this far down the page

How big are the air pumps on the cc out there say in the 4' to 6 ' range

Anybody with a 4'to 6' skimmer out there that knows there air pump output pressure



Anybody thanks
pacmans

 

[Snailman]

Hi snailman and anyone who read this far down the page

We started out with an air pump for this and an air pump for that and I got real tired of listening to them all buzz and keeping them all working. I bought an indistrial strength air pump. It is a Medo ACO902. It pumps am minimum of 1.94 CFM at a maxium pressure of 6.4psig. It is a linear piston air pump and they run for years and when they die you just replace the $35 piston. We drive three 5' skimmers and a bunch of other stuff with it. I think that normal people you a good pressure pump like the Tetra Luft.

 

[Flatlander]

I use a Tetra-tec DW 96-2. Its the biggest they make/made.
Cannot crank it wide open on the 6ft. by 3in.skimmer or the 3ft. by 4in. model I tried.
Thus the reason for building the BIG one,.

So do you guys think the smallest Iwaki 20rlt would pass to much water through a 6ft. by 4in?
Snailman, would not the 1in. return allow for more air to be pumped in as there would be no backing up from to much water flow. I am valving them also as per yours & KW,s instructions from the previous thread.
Thanks for the reference,s guys. Going to find them. I have read some.

I just feel I must have more water passing through. I feed my 170 a ton of food. When I did this to my 70, the Euroreef handled it fine, but I feel its creeping up on me in this tank as the Euroreef may be to small for the load.

 

[LiquidShaneo]

Hehe. Yeah, Snailman, I'm sure you got tired of hearing all those airpumps. I know it can get old after awhile. Sounds like a Tim Allen setup for that airpump! I've got 3 running in my den right now to power my airstone modified BakPak and my prop tank. Oh, in case you're interested in seeing my prop tank, take a look @ this: http://liquidreef.freeservers.com/prop.htm . I did some pretty unique things to acheive flow in my prop tank -- without the use of powerheads none the less! No more powerhead screens to clean and no more worries that my powerheads will short out in the tank either. The only actual electrical device I have in there anymore is a 100 watt heater. You may want to look @ this Snailman as it would be *another* use for your industrial strength airpump.

Personally, I'm running a Tetra Luft pump on my BakPak right now and it's rated to 7 psi. I plan to use that on my 4" diamter 4' high cc skimmer. I know that there are others that are using this same pump on higher diameter skimmers and it's working fine for them. I would definitely say the Tetra Luft will work well for you Pacmans. Here's a little bit o' trivia for you: for every 2.3 ft of water depth you go down you increase water pressure by 1 psi. So for example if you have a 4' high skimmer, the water pressure at the bottom of the skimmer is as follows:

Bottom psi = 4 ft x (1 psi/2.3 ft) = 1.73 psi

Considering that the Luft will pump against *7 psi*, you could pump air into a skimmer that's 16 ft high. That's a HIGH skimmer. lol

In case you're wondering, I purchased my Luft from Pet Warehouse on the net: http://www.petwhse.com/ for about $35 or so.

golfsuper: I'll definitely keep the 4" acrylic option open! btw...how much do you want for it? Feel free to e-mail me off-list @ chemistboy@excite.com.

Doug: I'm not sure what the flow rate of the Iwaki 20 rlt is. Sorry... A cc skimmer for a 170 should use a 6" diameter pipe with a flowrate of 130 gph for optimum nutrient export. Now you could also go with two 4" diameter cc skimmers or four 3" diameter skimmers inline and that would give you the same net area as one 6" cc skimmer. It's entirely up to you. I would definitely valve any pump running the skimmer as it will allow you to fine-tune the skimmer performance. I would use a gate valve over a ballvalve as you have a finer control over flow using a gate valve vs. a ballvalve.

I'm actually planning on using a 1" return on my skimmer just because I'm concerned with a smaller diameter return line somehow plugging up. I'd hate to come home to a flood b/c I undersized the return lines. I also plan to make an emergency overflow pipe from the skimmer collection cup back to the tank just in case a line does get plugged and the skimmer starts to back up. The water that backs up into the collection cup would then go thru the pipe and empty into the tank. Yeah, the skimmer would not function during this time, but hey, it saved my hardwood floors!

Plans at this point are to document how I make this skimmer and I'll post the results to my webpage. I also plan to summarize Escobal on that webpage as well using the published equations and charts. This is one thing that I have *not* seen anywhere on the net...

Thoughts?

liquid

 

[KW]

With the only exeption being the Euroreef pump, IMO, all other skimmers using venturies consume for too much electricity for the amount of air they produce. Any venturi can be put on a closed-loop; thus, allowing the air production and water throughput to be seperated. Another means to accomplish this seperation is the use of a seperate sump, for the skimmer, where the flow into the sump is controlled.

Linear piston and linear diaphram pumps are available with covers. Covered pumps will have sound ratings around 33-38 db. I am aware of Aquatic Ecosystems covered pumps and Gast covered pumps. If you know of some others please list them.

I was thinking about getting a Euroreef skimmer but, after thinking about it I decided that the money would be better spent on a powerful air pump.

To date, the only limitation I have had with my air-pump powered skimmers has been the air diffusers. I just could not get enough air to pass through the diffusers without either: (1) making the bubbles too large, (2) creating too much agitation within the skimmer.

I just made a prototype air diffuser that I have been testing for a week now. It looks very promising. This air diffuser has the bubble producing surface area of 18 6" air diffusers and has significantly less back pressure than any wooden air diffuser I have ever used. The prototype air diffuser is made from wood and uses less than 1/3 of the wood that would be used to build 18 6" stones.

The only unkown of this diffuser is it's durability. I tried to burst it with my Medo-602 and it would not split. Now, I'm just waiting to see how it holds up to two months of use. If it lasts for two months, I would like to have some other CC users try it out

 

[Snailman]

Linear piston and linear diaphram pumps are available with covers. Covered pumps will have sound ratings around 33-38 db. I am aware of Aquatic Ecosystems covered pumps and Gast covered pumps. If you know of some others please list them.

I got my Medo ACO902 from http://www.aquaculture-supply.com and yesterday I bought a Medo ACO602 on Ebay. Priming up for my 6" Reverse Carlson Surge Device.

 

[Snailman]

I'm actually planning on using a 1" return on my skimmer just because I'm concerned with a smaller diameter return line somehow plugging up. I'd hate to come home to a flood b/c I undersized the return lines. I also plan to make an emergency overflow pipe from the skimmer collection cup back to the tank just in case a line does get plugged and the skimmer starts to back up. The water that backs up into the collection cup would then go thru the pipe and empty into the tank. Yeah, the skimmer would not function during this time, but hey, it saved my hardwood floors!
Thoughts?

Look here -> http://www.precisionmarine.com/Accessories/Waste_Collector/waste_collector.html for a solution to the skimmer flood problem. I just built a DIY copy of three of these for our CC skimmers.

 

[YZ]

Hey golfsuper I'll take that section of 4" acrylic if shane don't want it.

I'm wondering if you guys run your water into the skimmer in a tornado like way. I've heard a few times in this thread that if you put too much air into the skimmer they get too turbulent but I would think if the waters flowing tornado like inside the skimmer that it would be hard to make too much turbulence.

Also don't berlin skimmers have a little piece of acrylic in the very bottom of the risor tube so it'll make the water less turbulent right before it starts to make foam.

 

[LiquidShaneo]

Snailman: Dude, that collection cup idea WROX! You mind sending me a pic of that DIY project as well? I've already hit you up for a ton of pix already... lol

KW: I'd be interested in hearing more about your airstone if it's all of what you say it is. You want another prototype tester? I'd be willing to do it!

liquid

 

[Snailman]

LiquidShano... The pix will be on the way soon.


KW... I would be more than glad to do some beta testing right now. We have three CC skimmers so I could do a comparison test. Feel free to email me.

 

[Flatlander]

Liquid, thanks for the figures. The Iwaki pushes 500gph. Guess thats to much by your figures.

Now that something new we have not talked about KW. Are we saying that my turbulence problems and large bubbles could be partialy caused by to small of an air pump?

 

[Snailman]

To date, the only limitation I have had with my air-pump powered skimmers has been the air diffusers. I just could not get enough air to pass through the diffusers without either: (1) making the bubbles too large, (2) creating too much agitation within the skimmer.

Chen's artice in 1994 Aquaclture Engineering found that with increased air volume in the skimmer the air superficial velocity increases there by decreasing the length of time it take for the bubble to rise so it is exposed to less gunk. The real bad part is that as the superficial velocity increases the bubble size also increases. Protein removal decreases as bubble size increases.

This is why you need a larger diameter skimmer tube to increase the air flow a lot.

 

[LiquidShaneo]

I think that's part of the reason why the Euroreef skimmers work better than other venturi's: their diameter is *much* larger than I've seen listed for other skimmers on the market for a comparible sized tank.

Oh, thanks for the pix Snailman! That self sealing skimmate collector looks pretty slick! Now I've got another DIY project to work on after the skimmer is complete. My wife is gonna love this...

Another question Snailman: how much contact time to you estimate your 5' high skimmers have anyhow?

Thanks!

liquid

 

[KW]

Snailman,

Chen's artice in 1994 Aquaclture Engineering found that with increased air volume in the skimmer the air superficial velocity increases there by decreasing the length of time it take for the bubble to rise so it is exposed to less gunk. The real bad part is that as the superficial velocity increases the bubble size also increases. Protein removal decreases as bubble size increases.

This is why you need a larger diameter skimmer tube to increase the air flow a lot. [/B]

IMO, I think the velocity at which the bubbles exit the airstone have an impact on the skimmer's performance. If one is pushing 1cfm through 5 square inches of bubble producing surface area one's bubbles will have much more velocity than he who is pushing 1cfm through 65 square inches of bubble producing surface area.

IMO, too little bubble producing surface is similar to putting a jet-nozzle onto a garden hose.

I'll e-mail you in a a few days.

 

[Snailman]

Oh, thanks for the pix Snailman! That self sealing skimmate collector looks pretty slick! Now I've got another DIY project to work on after the skimmer is complete. My wife is gonna love this...

Another question Snailman: how much contact time to you estimate your 5' high skimmers have anyhow?

I looked at the ad for the Waste Collector and thought that it would be a snap to build. It turned out to have more fabracation than my skimmer or my dual chamber calcium reactor by a large margin. If you need any help feel free to ask.

I do not have a clue what the contact time is.
I did a lot of looking at large diameter pipes and fittings for them last night. Large (8" - 10") fittings are very expensive. This makes it look like using a PVC tube if I can find one locally or getting an expensive acrylic tube mail order and build all of my flanges out of acrylic. I found a place to mial order large diameter PVC pipe but they wanter you to take a 100' feet of it.

I have three heaters in my tank and the sucker cups that they are mounted with keep coming loose. Yesterday's project was to cut a piece of acrylic and drill it for the three heaters. I took the sucker cups off and bolted the heater clamps to the acrylic sheet with nylon bolts. Now they will stay put.

[Edited by Snailman on 12-24-2000 at 11:44 AM]

 

[LiquidShaneo]

Quote from KW:

I think the velocity at which the bubbles exit the airstone have an impact on the skimmer's performance. If one is pushing 1cfm through 5 square inches of bubble producing surface area one's bubbles will have much more velocity than he who is pushing 1cfm through 65 square inches of bubble producing surface area.

I think you are pretty much just restating what Snailman said in his previous post. If you push a bubble out slowly, you will end up with a finer bubble. If you push a bubble out *fast* you will end up with a larger bubble. A finer bubble will travel up the water column much slower than a large bubble because of friction/buoyancy constraints. This difference in velocity and relative surface area greatly affect the amount of contact time and protein removal from the water column.

Snailman: Yeah, after i got your pix I realized that was probably going to be a pretty involved skimmate collection container. I will say this: it certainly looks much prettier than my 1 gal milk jug which I use to currently collect my skimmate. I like the option of having a carbon filter on the skimmate collection container as my wife HATES it when she walks into the den and smells skimmate. I may have to somehow incorporate that option into my collection container...

Oh...my wife almost killed me last weekend when I emptied out my skimmate into the bathroom sink while her parents were over for the weekend. That schidt smelled *nasty*. For some reason she's OK with smelling the cat box but not skimmate... Go figure...

 

[Snailman]

Snailman: Yeah, after i got your pix I realized that was probably going to be a pretty involved skimmate collection container. I will say this: it certainly looks much prettier than my 1 gal milk jug which I use to currently collect my skimmate. I like the option of having a carbon filter on the skimmate collection container as my wife HATES it when she walks into the den and smells skimmate. I may have to somehow incorporate that option into my collection container...

Precision Marine sells the small one for $70 and the large one for $100. If you only need one it may be easier to just buy it. I needed three of them and I already have the tools. I also had scrap acrylic sheet and tube left over from other projects so all I had to buy was the ping pong balls and the plumbing fittings so that is why I DIYed mine. It was great fun also. I know how to make flanges now and that is going to be real handy on the 8 1/2" X 5' skimmer I am planning.


[Edited by Snailman on 12-26-2000 at 11:30 AM]

 

[KW]

I think you are pretty much just restating what Snailman said in his previous post.

No, not really. Snailman's previous post is about the total volume of air in the skimmer and its impact on the velocity at which the air travels through the skimmer i.e. air has less resistance than water. I'm talking about the relationship between the amount of bubble producing surface area and the introduced air.

Obviously, one could never reach the point of diminishing returns, in regard to Chen's study, if one's air diffuser can not handle the volume of air required to achieve this feat. This is where I am coming from. IME, it is quite easy to overpower a wood air diffuser. In fact, after switching from 13 cubic inches of bubble producing surface area to 64.5 cubic inches of bubble producing surface area I realized how little air it takes to overpower a wood air diffuser.

 

[Snailman]

KW right on. The subject of the article was the ratio of gas to liquid (air to water) and the total amount of air in the skimmer. P.R. Escobal's fourth skimmer law is "The theoretical volume of air in a skimmer can only be about 13 percent the volume of the skimmer." This is why to really ramp the air volume up you have to up the volume of the skimmer.