Skimming 101

[MikeS]

We want to make sure that the tank water sits in the skimmer for as long as we can so that it has a better ability to get protien hits.

That's exactly what I meant...

The venturi skimmers I have move water through the skimmer much faster than my old CC airpump driven one did...personally, I think it may have a huge impact on skimmer performance...

MikeS

 

[mojoreef]

Recirculating the water through the skimmer will allow for the whole process to happen again so yes it will help, but in the same breath that is the concept of the flowrate through the skimmer in the first place right??


Mike

 

[Scooterman]

I was told by Barry from Aqua Medic USA, a few years back that for my turbofloater 1000 to work properly I had to slow the water coming in as slow as possible just a trickle, the water inlet is fed separately from the needlewheel pump so that pump didn't push much water just enough to suck air in. This little skimmer outperforms my new skimmer 3 times bigger but made differently.

 

[mojoreef]

Ok so then the question becomes, why?? In your case one can assume that the slowing down of the water input created more contact time in the skimmer and the raw water, probibly based on the fact that the turbo floater had a poor air injection rate. So what can you do to your current skimmer to take advantage of its size and make better skimmate??


Mike

 

[Scooterman]

LOL dude, If I knew that I would be jumping for joy right now LOL. Honestly I've been going rounds thinking about that very question & before I do anything to it I hope we get somewhere with this because I just don't know, have ideas but don't know. I was thinking of inserting a 4 or 6 inch airstone & adding more air to the skimmer as for one idea.

Ok skimmer specs.
900gph Gen-x needle wheel pump (loud compared to OR 35-- but works well)
Skimmer body 8 inches id tube by 27" tall, Neck is 6.5 inches tall by 4" diameter. 3/8" air line.

 

[MikeS]

Many DIY upgrades I have seen on venturi skimmers to make them more productive include the addition of an airstone. This makes sense...because in a venturi type skimmer if you slow the flow by choaking back the powerhead/pump...are you not also reducing the amount of air reaching the skimmer? If the air/water volume ratio is messed up in the first place, than logically seperating the two by adding an airstone and then regulating water flow through the system via a valve should make the skimmer more productive...

MikeS

 

[NaH2O]

Recirculating the water through the skimmer will allow for the whole process to happen again so yes it will help, but in the same breath that is the concept of the flowrate through the skimmer in the first place right??

I'm doing my best to understand this, and forcing my eyes not to glaze over. So, a higher flowrate will circulate water through the skimmer more times in a day than a slower flow rate, right? I'm thinking the small amount which gets recirculated (my skimmer is not one of the new fancy recirc skimmers) adds to the efficiency for what is lost in the skimmer style. I figure there is a bit of efficiency lost due to the skimmer body size/style? It isn't very tall considering some of the really tall skimmers out there, and the neck is relatively short...a few inches...maybe a little more. I'm sure there is some mathematical calculation to determine the dwell time for a bubble, but in my case, if there is only 30" for the bubble to travel up compared to 72" on another type of skimmer....the 6 ft. tall one would skim better because the bubble has an increased chance to pick up organics? I don't know if I'm making any sense with this, and I've officially glazed my eyes over. Maybe I'm confusing matters.

 

[mojoreef]

Ok Scott you have a pump bringing water to the skimmer that is 900gph, which is giving you a very large tank water turn over rate? you arent getting the degree of bubble production you need and your end product is clear. SOoo the concept would be to reduce the flow through the skimmer to maybe 3 to 4 times the tank volume per day and then increase the bubble production to give you a 20% saturation level.Sooo whats the problem????

Ok doing this to your skimmer. You will have to not use the genx to feed the skimmer as it brings to much water to the game, and reducing it will kill your already poor air production. So really you have a couple of choices. One would be to turn the genx into a recirc unit and feed the skimmer as mentioned prior with another pump or an off feed. Down side might be that the pump might crap out prior to giving you the air you need but hopefully not concidering the slow through flow rate. Or slap a smaller feed pump on in place of the genx and then go with the air stone that will give you the correct percentage of air to water mix. If you go either way I would feed the water as high in the unit as you can. you wouldnt need to drill another hole just plub you way up internally.


Mike

 

[mojoreef]

So, a higher flowrate will circulate water through the skimmer more times in a day than a slower flow rate, right?

yep
Look at it this way nikki. If you were playing sumu pinball and you need to bump as many folks as you could in a given amount of time what would make you get more??? slowing the folks down so you could get to more of them, makeing the room bigger so it could hold more folks for you to get at.
So in you case you are saying that the room is still the same but some of the folks are dropping by twice. Does this make the skimmer more effective, Maybe but in reality their coming back anyway because the flow rate is bringing them back 4 times a day??

Mike

 

[Scooterman]

Wouldn't high turn over be just as good as slower turn over if they do come back 4 times instead of just once or is it the slow pace that actually allows better contact time?

So If I added an airstone, the air tubing would be inserted from the top neck with the stone attached & I just let it all the way to the bottom?

I guess the next topic would be ok, we're moving along with new ideas but before we can go farther, we need to establish formulas to size up things like stones, per given skimmer tube, also air cfm's per same unit? I know this went a few rounds before the beast hit the right combination right?

 

[mojoreef]

Its not just contact time its the hits or bombardment rate that pertains also. If you have a high flow for many returns, you sacrifice your bombardment rate, your contact dwell time and so on. If you think that you can get all that back by returning more times then I guess it might work, but I dont think the math works.


Mike

 

[steveweast]

Mike....do you feel that it is possible to have too much air in the reaction chamber....and if so, what would be the results, or signs ?

 

[mojoreef]

For sure Steve. The concept is that in order to have enough protien laidened water droplets in the reaction chamber you have to alot for a certain amount of water. Having to much air (bubbles) displaces the water so you end up with a bad percentage. and thus your hit totals go down. Its not that its a bad thing its just not as effective.
Some of the problmes you see are the formation of very large bubbles which end up breaking prior to getting to the sump, or rogue bublles that drive up the hamber breaking other bubbles. Also your over all bubble size uniformity get bigger and you reduce your surface area. It also forces you into a pure heavy wet skim mode, which is real hard to dial in and will produce a very diluted skimmate.

try the test to see if you have the correct percentages (20%)


Mike

 

[dgasmd]

Maybe I missed it, but how do you figure out this 20%? You are talking a water:air ratio of 1:4 right?

 

[mojoreef]

1 to 5 alberto. you turn aff all the sources of air and then take a measurement of the height of the water column in the skimmer. then turn the air back on and take another measurement of where the water column now sits, that should have raised 20% higher then the first measure

Mike

 

[dgasmd]

I see. So how do you come up with that 20% number as being optimal in the first place? Why not 40% or 70% or any other percent?

 

[mojoreef]

Well since its my age I like the number??lol Actually thier is a mathimatical formula for figuring out the volume of air in a skimmer chamber. The results of this calculation show that bubble will begin to merge once they reach a saturation point of between 15 to 20 %, no matter what size they are injected. Having less then that just effects the performance at stripping the water of protiens.

Dont make me re write the formula its about a page long, lol.

If one follows the math on all aspects of protien skimming, it really opens ones eyes to how far we have strayed off the path.


mike

 

[Scooterman]

When I pinch off the air line on my needle wheel the water level rises considerable, so when I open the air it drops several inches, is that how I determine the 20%?

 

[mojoreef]

Hmmm Scotty it should be the opposite, lol. When I turn off my air the water drops down to a level. Whe I turn it back on it raises about 4 inches.


Mike

 

[RedEyeReef]

When I pinch off the air line on my needle wheel the water level rises considerable, so when I open the air it drops several inches, is that how I determine the 20%?

My TF Multi 1000 does the same thing when I cut the air. I believe it does this because the needle pump is also the skimmer feed pump. When air is added the amount of water moving through the pump goes down (being replaced by air) thus lowering the water level in the skimmer when air is added. This is opposite of how my "Mojo Special" reef skimmer works because it has a constant feed pump and air being added via air pump & stones which adding air raises the water level in the skimmer.

So with that said, how to you measure the 20% rule if you have a non-recirculating NW pump that acts like this? I don't know if all NW feed skimmers do this, but my TF 1000 does.