Skimming 101

[Skipper J]

yes thier the amount would be dectated by the surface area. The bubble shouldnt break because of it, if anything it makes the bubble stronger.


Mike

Joey - I'm not sure about the limit of proteins on the bubble. I imagine it would depend on the surface area of the bubble. I don't think it would burst the bubble prior to the collection cup.

edit - I see mike beat me to it

Thanks!So loosing bubble thru distance travelled and organic load per bubble would not be much of a concern then.!

I'll continue on reading old thread on similar topics ...keep it coming I'm learning lot...

 

[mojoreef]

Thanks!So loosing bubble thru distance travelled and organic load per bubble would not be much of a concern then.!

that is one of the main keys lost in most skimmers Joey. The distance traveled relates directly to contact time, hit on organics and dwell of both air and water. Organics dont just jump ship right away, thier is a time factor involved.

Mike

 

[Skipper J]

Yes ur totally right !What I mean is that, the bubble w/ organic load will have more than enough time to travel to the collecting cup.What becomes significant now is the bubble size and density to maximize organic load traveling optimum distance with a given skimmer design.

 

[alizar185]

I think your right on nikki. From what little I've read that is. And that consists of "the complete book of the marine aquarium" by:Vincent B. Hargreaves. It's the best book I've read yet, and the only,lol.
Another quick question, I'm thinking of going with a Plenum System. Which requires plenty of water movement, an excelent protien skimmer, and likewise filtration. Any suggestions on which kind of filter I should go with? Any and all input to these vital questions would be helpful, thanx.
Steve

 

[mojoreef]

Skipper the concept of bubbles size comes in two folds. as per holding organics and protiens its the same concept used by DSB folks, the smaller the bubble the more ya get per volume of water and thus the more surface area avalable. the second part is the total volume of air in relation to water with in the skimmer. It has been proven that anything over a 20% ratio will cause the bubbles to blend and become larger. this is the first hurdle air stones folks run into. They all of a sudden have this mass amount of bubbles and with the turn of a dial they can get even more. The first thought that comes to thier mind is Whoooo Hoooo I know it was my first thought.In reality what they should be doing is looking for the sweet spot, the spot in which they are injecting no more then 20% volume air, that way thier bubble size stays proper and they are actually getting somewhere.

Some folks think more is better and this is so far from the truth no matter what skimmer you are talking about. Most organics/protiens attach to air bubbles through a process of dwell time, as in it takes an amount of time for the organics to phsycally attach. You can make or blow as much foam and so on as you want but it aint going to matter one bit if you dont have the contact time. Also its not going to matter how many times you throw the tank water through the skimmer. Remember PROTIEN SKIMMING is two processes. Mehanical (un-attaching the organic mole from the water mole) and then he chemcial (re attaching it to the air mole). the process of mechanial stripping is done sucessfully by most skimmer types. Injector types (beckett's, down drafts, aqua c's, neddle wheels and so on) the injection of air being so radicully mixed with the water seperates the organics from the water, but sadly that is where most skimmer stop. From thier it should be all about contact dwell time for both air and water with the now seperated organic/protien. If this time is not allowed to occur then the organic/protien will just attach back to the water once it leaves the skimmer. You can do this process a hundred times a day but the result is going to be the same.
What they rely on is that force. they create a frieght train of water with a bumper of foam, they foam holds all that can sit ontop of it ( look at it like ultra wet skimming) what ends up in the cup is partiulate organics (which is good) but virutally no soluable organics. If you have a skimmer that incorporates the dwell time, bombardment rate and the correct amount of contact time you get it all and you dont get the vast majority of the live critters that are caught up in the freight train.

anyway just some thoughts

Mike

 

[mojoreef]

alizar185 I am not sure of your question but why dont you start another thread and we can dive in.


Mike

 

[Skipper J]

If you have a skimmer that incorporates the dwell time, bombardment rate and the correct amount of contact time you get it all and you dont get the vast majority of the live critters that are caught up in the freight train.


Wow!!! The concept is "CRYSTAL"!!!!!Very well thought and explain!
Can we put a range of values on the parameter mention above?


Thanks Mike!

 

[mojoreef]

Oh man now your going to make me work, lol

Ok you want the skimmer to cycle the tank water twice, now on that use the formula. (tank gallons/gph through the skimmer)X 9.2= all tank water through the skimmer.

you want a good dweel time for the air bubbles. So the amount of time it takes the bubbles to rise AGAINST the downward traveling raw water. So something around 10 seconds?? an example if it takes 12 hours to cycle through all the water in your tank and your dwell time for a

You want a good bombardment rate. As in the amount of time the water moles get beaten up by the air moles and mechanically strip the water. A value of 10 (as in the water mole get hit 10 times by a clean air bubble on the way down).is really good. an example if it takes 12 hours to cycle through all the water in your tank and your dwell time for air bubbles is 10 seconds then 4300 hits will take place. So the slower the turn over the more hits take place example circ the tank every 15 hours and the hit total goes up to 9000. Or cycle the tank through the skimmer every 5 hours and the hit total goes down to 1800 hits. Now big thing here. If the water is traveling counter current to the air it is by far the best way. this way all the water that enters on the top of the skimmer must pass through all the air bubbles on the way up in order to leave the skimmer on the bottom. If the air and the water are injected at the same point the bubble is carried by the same water moles up the skimmer. As in they dont get to hit all the other moles.

Ok did I miss something??

Mike

 

[MINIATUS]

I think I understand all this dwell time ETC ETC. With my Turboflotor I have a feed pump that feeds 103 gph. Would i get better results if I slowed the feed time down.Or am I still not getting it. :?: If I understand no more than the tank volume in 24 hr would give me an ideal sitution.

MINIATUS :?:

 

[mojoreef]

Ok min give the the following

Pump that feed the skimmer in gph
Size of the skimmer,
Size of the venturi.
size of the tank


Mike

 

[MINIATUS]

Ok Mike

90 gal tank with 25 gal sump.
turboflotor skimmer with recirculating OR2700
Feed pump is rated at 106 gph.
Main tower of skimmer is 15 inchs and 4 inchs wide
Air tube iiside diameter is 3/16

Do these figures sound right.

MINIATUS :exclaim: :?:

 

[Scooterman]

Wow did I miss a ton or what LOL,
MINIATUS I posted pick of my TB1000, is that how yours is made, look back a few pages?

 

[MikeS]

.In reality what they should be doing is looking for the sweet spot, the spot in which they are injecting no more then 20% volume air, that way thier bubble size stays proper and they are actually getting somewhere.

Hmmm...gonna have to go deeper on that one for me Mike...

Lots of varibles determine bubble size, right?...pore size in the airstone, pressure in said airstone, Specific Gravity of the water is a big factor also ( the main reason skimmers don't seem to work well in FW tanks), turbulence and flow rate in the skimmer, ect, ect...

I get the point about the air/water ratio, logically it's definately a factor as well...but it's a lot more complicated than a simple question of ratios isn't it? Having said that, would it not be wise for any skimmer design to shoot for having as small an inital bubble size as possible, to help offset some of the varibles? Logically, if you start with as small of a bubble as you can, even if some merge into larger bubbles, these new larger bubbles are still small enough to be effective?

MikeS

 

[mojoreef]

Ok lets see if I can do this with out falling asleep.

Min lets call it 90 gallons of water if we take the rock out, so

your turn over rate would be just under 8 hours

The volume of the mixing chamber is about 1 gallon, so the water dwell time is about 33 seconds

the amount of air made is approx. 1 cfm. so again about .5 cfm per refil

Ok over all the air to water mix is a little high on the air side so look to dial it down. As in concentrate on the bubble size and not the amount. Your turn over rate is a little quick so turn it down to approximately 80gph. Your bubbles will reach the top in about 3 seconds. so your bombardment rate is about 11 which is really good.

Conclusion: As you figured your flow through rate is a bit quick so just turn it dow a touch, your air mix is also a tad high so put a valve on it and adjust down. Bombardment rate is very good and this skimmer is also counter current so it take full advantage of the hits.

You close buddy.


Mike

 

[mojoreef]

Damm Mike I almost excaped this thread, lol

Lots of varibles determine bubble size, right?...pore size in the airstone, pressure in said airstone, Specific Gravity of the water is a big factor also ( the main reason skimmers don't seem to work well in FW tanks), turbulence and flow rate in the skimmer

Sure if you use an airstone then yes pore size is important, thus the recomendation on its size. Specific gravity should be pretty static with in the small range we are talking about. Turbulance does not effect the bubble size, just its life span. flow rate again shouldnt pertain to its size.

Having said that, would it not be wise for any skimmer design to shoot for having as small an inital bubble size as possible, to help offset some of the varibles?

Sure thats always the goal, if you can get the size of bubbles I am refering to you are in the money, fine pore stones will get them and so will simple venturis. I am not sure on the other styles.

Mike the concept is to look to generate as small a bubble as you can. Personally from looking at the fine pore stones and the needle wheel skimmers I feel comfortable with them. On the injection systems such as becketts and injectors I am not sure as the box hides the bubble size that is made. I would have to imagine that it would could be concidered a hyper venturi. Maybe a beckett user could give us a size on it??


Mike

 

[MINIATUS]

Wow did I miss a ton or what LOL,
MINIATUS I posted pick of my TB1000, is that how yours is made, look back a few pages?

Looks just like mine, pump and all. Mike I need to visit the pet shop tomorrow and get a few things than I can go from there.

MINIATUS

 

[MikeS]

Damm Mike I almost excaped this thread, lol

aww...I'd have redirected you back to it Mike, you know me... :lol:

. Turbulance does not effect the bubble size, just its life span. flow rate again shouldnt pertain to its size.

Sure, but isn't that all one in the same when it comes to the end result? For example, if your skimmer is too turbulent to give the bubbles an effective lifespan before they merge and become too large to be effective?

Mike the concept is to look to generate as small a bubble as you can.

Mike

That' s what I'm getting at....and trying to relate bubble size to the function of the skimmer as a whole...

MikeS

 

[NaH2O]

MikeS - you're confusing me - just when I thought I was starting to understand.

I'm not sure if you can look at flow rate as turbulance - its just water in....water out. How those bubbles/airflow are combined with the water make the turbulance? Also, turbulance would be part of the overall height and diameter, too, don't you think? If my skimmer was only 5 inches tall...the bubbles would be subjected to more turbulance than they are being 20 inches tall. Same with diameter....if my skimmer was only 4 inches in diameter....the bubbles would be in more turbulance than with my skimmer being 8 inches in diameter. The flow rate would be the same, though. That's what my brain tells me with little sleep anyway . OK - I need to stop talking now...

I had a thought about my skimmer....needle wheel. When I watch the bubbles come into it....they swirl around due to the action of the needle wheel. Wouldn't this increase the dwell time? Perhaps not a significant amount.

 

[MINIATUS]

Hey Mike
I bought a mini pump rated at 80 gph and a valve to slow the air a bit. Its a whole new skimmer. The junk its removing is awesome.

Scooterman
you said you made some changes to the TB1000 what were they.

MINIATUS

 

[mojoreef]

For example, if your skimmer is too turbulent to give the bubbles an effective lifespan before they merge and become too large to be effective?

Sure. but the turbulance does not necessarily mean its going to make a larger bubble, it might make the same size bubble. the down side of turbulance is the distruction of the bubble and thus the loosing of the protiens attached. Regardless you are looking for the smallest bubble to be produced. The over all turbulance of the skimmer should be very low, but if you take the figures listed through out, EX: the right flow through rate, air to water mix, and dwell times then you shouldnt have turbulance?

Nikki

I'm not sure if you can look at flow rate as turbulance - its just water in....water out.

Flow through rate can make to much turbulance, just look at some of those skimmers with thousands of gallons per hour running through them.

Also, turbulance would be part of the overall height and diameter, too, don't you think? If my skimmer was only 5 inches tall...the bubbles would be subjected to more turbulance than they are being 20 inches tall. Same with diameter....if my skimmer was only 4 inches in diameter....the bubbles would be in more turbulance than with my skimmer being 8 inches in diameter. The flow rate would be the same, though

sure, just stay with in the guidelines and you should be fine

I had a thought about my skimmer....needle wheel. When I watch the bubbles come into it....they swirl around due to the action of the needle wheel. Wouldn't this increase the dwell time? Perhaps not a significant amount.

Dweel time for air should take in concideration all those things. flow rate going through it creates an indirect path, and also puts back pressure on the rise of the bubbles. I did incorporate that into the formulas though.


Mike