Skimmer Turnover Rate

[NaH2O]

I need some help with a concept. I tried reading the skimmer conversation thread, but my eyes started to cross (if this has already been covered, then please put up a link to the post). It was suggested to me over the weekend that skimmers will be more efficient if they are only turning over the tank volume somewhere around twice a day. The slower flow into the skimmer is better. Is the concept that the water gets skimmed better because it is in the skimmer longer? I am really confused by this. I thought the more times the water volume goes through the skimmer the better? Maybe it doesn't make a difference?

 

[mojoreef]

Hmm it really depends on the skimmer. Skimmers that have to use High pressure pumps such as becketts, downdrafts, and other simular devies onperate under the principle of less effective skimming but make up for it with high turn over rates. Other skimmers such as the needle wheel, venturi, air stone are more effective and thus do not need the turn over rates.

So you really kinda of skim per the skimmer concept you have. Personally even though mine falls into the more effective I still like to skim as much as possible.



Mike

 

[bigdave]

I think Mike sums it all up with that. I prefer the high pressure beckett style so I can cycle thru more water in a day. There is nothing wrong with the needle wheel skimmers they are very effective like the euroreef you have. Good luck I think you have a great skimmer now. Dave

 

[btuck]

The basic thought process that I had when I brought this up was this:

1. The slower moving water will lengthen the contact time with the bubble, thus allowing more nasties to attach themselves.

2. Turbulence within the skimmer is greatly reduced. The smoother the ride the better.

I was thinking this would be best achieved using a counter current air driven skimmer. I have recently been told of a monster of a skimmer using massive airstones, I would love to see the plans for this skimmer.

I have an idea for a dare I say new idea for a skimmer. The basic plans are the same of a counter current air driven. The only real difference is that the water would enter the chamber the chamber would fill up and both the input and output would close. The water would then be saturated with bubbles and cleaned for a short period of time. The valves would then open and new water enters. Somewhat like those rides at a theme park. The true advantage of this would be the lack of Turbulence within the chamber. I think the disadvantages would be that it wouldn't be used on a large system, and that I have no idea on how to make this work. I.E. the entrance and the exit opening and closing at the right time. The pump could be operated with a float valve. Ok but I'm just rambling now. It's 4 a.m. only 3 more hours of work.

 

[NaH2O]

Hey Brian - glad you jumped on this thread, and you added what your thoughts were about the turnover of the skimmer.

I have recently been told of a monster of a skimmer using massive airstones, I would love to see the plans for this skimmer.

Here's the thread to the skimmer I was talking about (the airstones come into the picture later in the thread). It is currently being redone, because Mike broke it lol, but the new one, I'm sure will be better than the first version. New Skimmer

 

[bmtpfgh]

Isn't the turnover rate through the skimmer strickly dependent on the rating of the skimmer pump?

 

[bc_slc]

the question nikki is asking is not what IS the rate through my skimmer, but rather what SHOULD THE RATE BE through my skimmer. Some believe that the skimmer should skim as much as possible as fast as possible, turning over the total volume of the tank many times in a day. Others believe that you should only skim ata certain "most efficient" rate of around 2x/day. I myself don't really understand why you would not want to skim as much as possible....

 

[jlehigh]

Take a look at the theories presented in this Skimmer 101 article. I am not familiar with the studies and logic used but they have specific calculation for water turnover and suggest any air volume greater than 13% of the overall volume of the skimmer will cause diminished returns. (These are mostly based on Counter Current designs)

http://www.hawkfish.org/snailman/skimmer101.htm

 

[mojoreef]

Hi btuck and welcome to Reef Frontiers.

Contact time is an issue but it is almost impossible to be able to measure that. If one could follow the one bubble once entering the skimmer until it leaves the cup, well I think it falls well over the longest contact time needed (120 seconds I believe)

bc_slc its really hard to distinguish that though. As I mentioned thier is methodolgy for both systems. As per the those that want to skim less or more, well that is a whole other debate. One that I am on your side with.


jlehigh funny My copy says this

Make the skimmer reaction chamber as tall as possible to maximize the contact time that the water has with the air in the skimmer. Pump as much air into the reaction chamber as possible.

Mike

 

[jlehigh]

Are you pulln my leg Mike? The only thread in the article that ressembles that in mine is:

Make the skimmer reaction chamber as tall as you can to maximize the total contact time that the water has with the air in the skimmer.

Regardless I found it interesting that certain forms of waste take longer than others to cling to the oxygen bubbles. Now here is the important question I don't have the answer for:

What percentage of the nutrients in our tank are "slow clingers" If it turns out it is very small and it is an amount that can be negated through biological filtration then turn as much water over as you can with as much oxygen you can without creating negative turbulence and get the majority of the waste out! I would say this is what Becketts do..

I just increased the air input and closed the gate valve a bit more on my DIY Euro style last night to see what would happen. This means I have less turnover, more air, and more contact time. We'll see what happens.

I find it difficult to talk about water turnover in skimmers without talking about the volume of oxygen. I would think the two are married and should be relative in calculations..

 

[Maxx]

JLEhigh,
This would be a PITA...but if you notice a difference, I'd be interested in knowing your flowrates through your skimmer.

Nick

 

[jlehigh]

I'd be willing to do it if I thought the results would relevant... In order to test the flowrate I would need to do a bucket test on a vertical drain. So a few issues here.

-Since I didn't perform a test prior to the adjustment we will never know what the throughput was
-If I stick an L-shaped pvc on the vertical drain It could possibly slow the drain enough to overflow in the skimmer
-Given the tight fit the skimmer is in my sump I would also have to remove the skimmer from the sump to be able to drain into a bucket

hmmm the more I think about it the more issues I see... HAY! wait! I can measure the skimmer body and calculate the volume, then drain the skimmer, turn it back on and time how long it takes to fill.

I'll give that a go

 

[mojoreef]

jlehigh the article that you referenced is using references from Escobar's Book "Aquatic Systems Engineering: Devices and How They Function" Which is a great book if you can get your hands on it.
The peice I quoted was from that book. I think the fellow that wrote that article was making an assumsion, but I could be wrong.
I cant see the effect of over saturation on air input, besides violence. The more bubbles the more surface area for protiens to attach to seems logical to me. The longest contact time for a protien is around 2 minutes approx. Now thats pretty hard to measure so I would say its a best guess really. If one were able to follow a bubble through the skimmer I would say that should be to hard to achieve, but again best guess.
Protiens are pretty popular amost reef critters so I would imagine that it would be used up.

I will do a little digging and see what I can find for ya.


Mike