Downdraft skimmer update.

[bryang6286]

my setup is basically a 200g of salt container (not really 200g but for making that much water) and i have a gravel cleaning siphon things out the end. the only way i am going to be able to adjust it is through where in the siphon the inverted funnel is, so if i want a smaller siphon i put it farther down. my question is where should my water level be? should it be right where the salt container and siphon meet, an inch up into the siphon, or a little below?

 

[dugg]

I'm not getting the picture here, but the water level should come up to level with the top of the main skimmer box or bucket. Then you should have 3 to 9 inches of riser tube for the bubbles to rise up in and collect the skimmate.

 

[bryang6286]

makes sense, i just reread my post and i realized that i made practically no sense, but what you said completely answered it. thanks. ill post when i get it set up. im still working on a overflow box. right now i have a powerfilter that i cut a hole in the bottom similar to an overflow box. I am just not sure what i am going to use to make sure my utubes get only surface water.

 

[captbunzo]

A second, internal overflow box. Water flow into that box and then the power filter sucks it up and over.

 

[bryang6286]

im gonna use u-tubes with the powerfilter because the power filter doesnt pump out enough water. where can i find an internal overflow box? I have another overflow box and was thinking that the internal boxes of the two might have to be the exact same height or one of the sumps/skimmer would overflow. Im not to sure.

 

[captbunzo]

You might find one of those boxes that fish stores hang on the outside of a tank to put fish in when they are selling. That could probably be modified pretty easily to fit inside of the tank, opposite of the power filter.

Big question - how the heck do you plan on balancing the flow rate of your power filter and sump return pump? That will be near impossible.

That's why people have to use siphons.

 

[bryang6286]

well what you do is you make the overflow's outlet/exhaust tube raised to either the water level (if you do not have an internal box in your tank) or some level inside your internal box . this way when the water gets lower the siphon starts sucking out less water because the water levels are the same inside the overflow box and where it is sucking the water out from i.e. the tank or the internal teethed box. that probably doesnt make much sense but i gotta go. maybe ill explain it later

 

[bryang6286]

i just built one but the bubbles are comnig up to big. any suggestions?

 

[Spikehs]

could someone post a diagram of what the overflow should look like? I got a description from Wayne on how to do it, but still can't quite visualize it. Any help would be appreciated. Thanks.

 

[dugg]

This is pictures of Waynes overflow and plumbing.

 

[dugg]

bryang6286, kind of hard to say without seeing what you have, but you may need to add an airstone, if you don't have much flow going into it.

 

[dugg]

Spikehs, there is a piece of egg crate that lays over the top of that silicone, with a plastic bag covering the front 2/3 of it.

 

[Spikehs]

Spikehs, there is a piece of egg crate that lays over the top of that silicone, with a plastic bag covering the front 2/3 of it.

sorry for being stupid, but i just can't see whats goin on in the pictures.... anyone handy with the diagrams?? thanks.

 

[captbunzo]

Good god - I woke up this morning and my skimmer collection jar was mostly full of thin skimmate. So I raised the funnel up a bit.... All the way to the top and the foam is still rising strong.

Usually it only gets an inch or two up the tube. Wowzers...

 

[jacmyoung]

For a smaller tank or low flow system, if you have to add an airstone to aid the skimming, why not just buy a Lee's airstone-driven counter current skimmer, they are not expensive at all.

 

[barryhc]

dugg, I've read both this, and captbungo's thread, with most of the related links today, and I'm exceedingly impressed!

I've been toying with this same idea for about a month now, while designing my display-sump-refugium. I was about to "chuck" the idea for lack of R&D time when I found these threads today, and "impressed" is quite the "under-statement".

For reasons that I won't bother you with, the available space I have for the skimmer "housing" is restricted to about 4" x 7or8".
I have 450 gph draining right now thru a 1" tube, and a huge volume of 1/16" to 3/16" bubbles. I have about 16" of vertical "wet height" available here, and I'm still "on paper" with this, so I can fudge around, a "little bit", not much.

The above available "wet space" comes to about 1 3/4 gal. , and I would have to put any power head inside the housing, from the bottom.

You thoughts here? Do I have a chance to make this work in such a confined space?

Thanks for all the great work! > barryhc

 

[captbunzo]

Barryhc:

I think that your space will do just fine for the construction of a skimmer. I think that the recirculation is a good idea, i.e. the powerhead. And an added airstone is a good idea as well. However, there are some other things that you can think about to help out.

Ok. First you have to find a way to create air bubbles. The air from the downdraft of your overflow will always help. However, in my experience, it will not be enough. You can add more via compinations of a venturi, a needle wheel, and/or a air stone. Basically, we are looking for lots of litle tiny air bubbles.

And Second you need a way to get skimmate out of the skimmer. As you surf around our threads, you can see the inverted funnel that works pretty decently. However, my preferred choice would be to build a more traditional skimmer cup.

Lastly, it would be great to have a way to control the pressure in the skimmer. The best way to accomplish that is to make the skimmer body enclosed and put a ball/gate valve on the skimmer output. That will allow you to adjust the pressure in the skimmer and control the skimmate output a little more.

BIG IMPORTANT HINT

Go find the expert forum called "All Things Salty", moderated by Anthony Calfo. Then find in the sticky threads at the top the thread about skimmer performance.

Then read it. All 30 pages or whatever. It's well worth the read...

 

[barryhc]

Thanks Paul, actually I "skimmed" all of it ( pun intended ), and actually read over 20 pages of it carefully, along with about another 40 pages of "links" just today. ( I've been at it for about 6 1/2 hrs. now ) I will review all of it again, before I commit to plastic, no doubt.

On the tiny bubbles issue, I was wondering if it makes any sense to put a "second path" near the bottom of the drain tube, just above the housing fitting, with a needle wheel impeller in the pump, just to chop up the existing air water mixture, right before it gets to the skimmer housing. This would be out from the drain, thru the pump, and back into the drain, and using "drain air" only. Therefore it could not ever leak.

I only have about a 3 ft. drop, so it might eat up too much "head" in my case, but it could be an interesting alternative for systems with more "headroom".

I agree on the collection cup design, and since your still "hot on that issue", I think I'll just sit back and follow on that one.

On controling skimmer pressure, we have to screen the intake carefully I assume, and also monitor carefully as well that we don't adjust so close that something awful happens when were gone for three days. Am I understanding this correctly.

Thanks so much, I just love this thread! > barryhc

 

[captbunzo]

First, concerning the collection cup, I am not going to be able to get to that for probably a month or two. So, errr, not so hot at the moment...

Second, concerning "screening" the intake carefully, I am not sure what you mean. If you are talking about some sort of prefilter, then indeed you don't want to do that. You want all that nastiness to go straight into the skimmer.

As for the bit about monitoring carefully, I think you are correct in that you'd want to be careful to avoid any problems.

 

[barryhc]

captbunzo, I'm thinking primarily in terms of the "back pressure" created, by partially closing off the "final-drain-path", causing the flowrate thru the drain tube to become less than that of the "return".

Does that make any better sense?

Any comment on recirculating the "drain flow" just above the entry to the "skimmer body"?

Thanks again > barryhc