Skimming 101

[Scooterman]

Hi ToddLaCo Welcome to RF! I really like this thread but to be honest I need a refresher on it, Mike Is the expert on the math part, It still boggles my mind so if you read all this & still don't quite understand the math, don't feel alone. It is always good to bump this thread up & maybe get more input, in the meantime I'll try & read it throughly again because I just need to Sorry I couldn't do better with the formula per say but we'll take another stab at it again.

 

[ldrhawke]

I am not sure if anyone is still monitoring this thread, but if so I have a question.

First off I want to say this is by far hands down the most informative thread I have ever seen concerning skimmers.

I am planning to build a counter current skimmer for a system that holds approximately 400 gallons after subtracting sand, rock, etc..

First off I noticed that "Tiny Giant" asked in an earlier post if 10 was an optimum bombardment rate, and there was no answer. Is there a value given for the optimum bombardment rate?

I came up with the following skimmer for 400 gallons using Tiny Giants spreadsheet considering the value of 10 was correct for bombardment.

Skimmer Height - 72 inches
Skimmer Radius - 9 inches
Skimmer Feed Rate - 6 GPM (360 GPH) after head loss

This sounds large, but very doable. Please let me know if this looks correct.

One thing I didn't see mentioned in this thread, how do you determine the length and diameter of the riser between the main body and the collection cup? I wouldn't think this could be just any random size. Are there certain dimensions for the collection cup also?

I haven't been on this thread or list for awhile. Now that I have been using my skimmer for a number of years I have come to the conclusion, " Human nature is to often make the simple complex"

Sizing a skimmer isn't as complex as we make it. My skimmer is over sized for my system, and that is probably the safe way to make any skimmer. How do you know it is over sized? It will over skim and stop skimming periodically. If it never stops. Make the skimmmer larger.

The skimmer can't be designed simply based on the size of the tank. It is sized based on load. The load will vary from tank keeper to tank keeper and vary based on the how the tank is fed and what you have in the tank. A skimmer performs based on the organic waste loading it sees.

Obviously you need a starting point to size a skimmer in the first place. I suggest, within reason, simply build it as big as you can fit into your system. You can't over size a skimmer, only under size one. But it isn't based on a simple tank volume formula that skimmer manufacturers often lead you to believe. And it isn't based on the complex formulas many have tried to develop to make the simple complex. It is based on waste loading from your individual system and the amount of life you are supporting. If you feed heavy you need a larger skimmer. If you feed lite you can use a smaller one.

My skimmer maintenance consists of emptying a gallon overflow bottle once a week and cleaning the skimmer cup once a month. Sometimes the over flow container has a lot of black goop other times it has a lot less, depending how heavy I have been feeding. Once in great while it over flows, if I change food and amount.

I have a heavy bio load...too many fish for tank size. But, the over sized skimmer compensates.

A few photos to bring this thread back to life. My point is simple...just buy or build the biggest skimmer you can afford or fit into your system.....and relax. It isn't as exact a science as many selling skimmers would want you to believe. Just buy a big one. Bigger is better...

This is the smallest and cheapest Euroreef skimmer modified to make it taller.

Tank photo from a few days ago

The tank is a half barrel.....all the information is listed in the articles and writeups below.

 

[ToddLaCo]

Well, I just revisited the spreadsheet to check different configurations for the skimmer

I kept the 9" diameter and adjusted the height of the skimmer. The bombardment rate stayed the same no matter what height I used. The height must change the water dwell and air dwell in relation to each other which held the bom. rate the same.

Now, when I changed the diameter it changed the bombardment rate significantly. The change in diameter increased the air dwell time and reduced the water dwell time.

I thought that I had somewhat of a handle on this, but it looks like I will have to do some more research.

I understand that you can't affix any hard numbers to what a skimmer should do in relation to air dwell, water dwell, bombardment rate since it is largely dependant on bio load (which in my case will be fairly high) but I wonder if there are some loose figures out there anywhere to start with. Basing it on the bombardment rate alone doesn't work.

 

[ToddLaCo]

Just re-revisited the spreadsheet and saw something I didn't notice before.

It asks for skimmer radius. Is this correct asking for radius or should it be diameter?

If radius is the correct measurement I am going to have to do a bunch more re-figuring. My 9" skimmer would actually be 18" diameter and that just wont work!!!!!

 

[Curtswearing]

Just re-revisited the spreadsheet and saw something I didn't notice before.

It asks for skimmer radius. Is this correct asking for radius or should it be diameter?

If radius is the correct measurement I am going to have to do a bunch more re-figuring. My 9" skimmer would actually be 18" diameter and that just wont work!!!!!

You might want to PM Tiny Giants or Crazzyreefer. I always assumed that the word 'radius' was used accidentally as a synonym for 'diameter'.

 

[ToddLaCo]

Thanks. I will PM one or both immediately.

 

[ToddLaCo]

Well, for anyone concerned and following this thread. I PM'd Tiny Giants and received an answer to the radius question. The term radius in the skimmer calculator is correct. So if you input 4", the skimmer will actually be 8" diameter.

 

[salali]

This is an amazing tank ldrhawke

 

[Spongerock69]

Hey Mike,

I'm new and would love to get into a discussion about the principles of skimming. As others have
stated, the real deal seems to have been obscured by unsavory manufacturing motives. I saw someone in
a previous post mention that their skimmer was overflowing suddenly, and that made me immediately think of
water level and that it was possibly back-flowing through the discharge..??

Anyway, please feel free to discuss principles...I need all the help I can get, thanks

Michael

 

[mojoreef]

You dug up an old thread Sponger, this one is a few years old. feel free to start another thread if you have some questions.

Mike

 

[xxkenny90xx]

Great thread, very informative

 

[monkeyseat18]

Anybody know of a great over the back protein skimmer?

 

[NanaReefer]

Anybody know of a great over the back protein skimmer?

Several! But for what size tank?


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