Need help w/ DIY HOB skimmer

[dzeadow]

Well, I thought I'd try my acrylic skills by making a skimmer. I don't have a sump so it's going to have to be a hang on or sit behing type skimmer. The max room I have behind my tank to comfortable move is about 5 1/2" and the height of my tank is 18". I've come up with a design for a recirc skimmer to sit back there or hang on the rim. One of my questions is, do you think w/ the size of the skimmer, would it be too much weight resting on an unbraced 18" high 1/4" thick piece of untempered glass? The skimmer I'm thinking will be 22" high (height of main "box") 12" wide x 5" deep. The reaction chamber will be 5x5 at the top. I'm not really wanting to thermoform a square base into a tube neck, so I thought I'd stick w/ a square collection cup design. The right side of the plan has 2 pipes which are for the recirc pump. I'm planning on using a Sedra3500 mesh modded. The skimmer will be fed w/ a MJ1200 or a NW Resun 225 (whichever will be more efficient). The inlet would most likely be 1/2" and the outlet 1".

Before I buy any materials or anything I'd like to get some opinions or design change ideas. I'm pretty open to anything. I was even considering putting a bubble plate at the bottom of the reaction chamber if it would do any good. Anyway, please let me know what you think, here's my idea, please don't crush the idea entirely!

[dzeadow]

BTW, you'll have to pardon my 2nd grade knowledge of google's Sketchup, I'm just barely learning it.

[Altpers0na]

im no expert...

but i dont exactly get your skimmate collection?

i would also go ahead and add a spot for an air stone...

the bak paks basically look just like that. that is what i have on my 20hex tank...

the only trouble i have seen is adjusting the skim cup height for goop thickness..

[dzeadow]

Yeah, like I said I'm not an expert w/ the Sketchup by any means. I'd basically have the cup tight enough to have a bakpak style rubber band on it to adjust it up and down. The bubbles would travel up the slanted acrylic on the cup and overflow into the cup. Not as efficient as a tube neck, but it should still work. I don't think I'd need an airstone w/ a mesh modded recirc pump and a NW feed pump... there should be plenty of air in there.

[happyface888]

I agree, the slanted cup is pretty affective on the deltecs mce600

Hmm for weight issues would adding more support holders on top help? You know the octopus bh100f the center has this slide in attachment that helps distribute the wieght.

[dzeadow]

Yeah, I was thinking of putting 2-3 triangle type supports on it if it wasn't going to be an issue. Plus a few of those nylon screws to adjust the bottom to level/plumb. Otherwise I can just let it sit on my stand.. as long as it's tall enough for the pipes to reach over the walls.

[happyface888]

Hmm for the feeder pump what do you think about using a sicce pump or a pump that has about 700gph there and having the venturi after the outlet. That way it ram alot of air into the chamber, your reaction chamber is 5x5 which is pretty big after all.
I'd stick a 1/4 venturi intake for maximum air draw.

[dzeadow]

I'd probably go something a little cheaper than a Sicce.. I guess it all depends on what the guru's say is the best. I thought w/ a smaller feed pump that it'd give the water/air more time to dwell in the skimmer, but maybe I'm wrong.

[luke33]

I'm not a fan of those collection cup's. What happens if it overflow's? Wet carpet. 5x5x18" tall? A sicce is going to be waaay to much. I'd think a 500gph pump is going to be about all it can handle. It just depends on how much you want to spend on it. The best would be the aquabee but you can get cheap pump's and get them to pull around the same. The octo 2000 being out of the question as its huuuge for a 500gph pump. I could get 12-15scfh out of the odyssea wp500 when i modded it. For 25bux it wouldn't be a bad pump to mess with. You also don't want your output so high in the reaction chamber, you need to utilize as much reaction chamber as you can.

[dzeadow]

1st, why would the collection cup overflow? it's still under the same principle that when the skimmate gets too high it'll overflow back into the skimmer, plus I could always add a drain line.

I'm with you as far as not overpowering the reaction chamber, that's why I originally thought a mj1200 would be ok or the Resun225, but both may be underpowering it. I like the idea of the odyssea, I looked at them on aquatraders.com after you mentioned them previously. If they're pulling that much air, the 500 would be a great feed pump. Do you think that the sedra 3500 is too much or ok for recirc'ing? I figured 1 or 2 layers of mesh or buying their needlewheel would probably be ok.

How far down would you suggest putting the output? I can always raise the skimmer height by putting those triangle rests lower on the body. I didn't think the inlet would be too big of a deal since it'd be 1/2" pvc in a 5x5 chamber, but I don't know much about this stuff, obviously.

[dzeadow]

maybe you were saying extend the inlet pipe down further into the chamber? That makes sense if that's what you were saying.

[dzeadow]

Does anyone know if it's completely necessary to thermoform the bottom of a skimmer cup where it meets a circular tube? Or can it be a flat square w/ a 3" pipe sitting in the middle? If that's the case maybe I can redesign the collection cup like that.

[luke33]

I'd make the collection cup like a remora's cup except 3" in diameter, that would be a good size for that skimmer. I was talking about recirc'in the skimmer with the 500gph pump. You always want to recirc with the larger pump. Your pry only going to need a small pump to fee that is around 100-300gph max since this skimmer is going to be for tank's around 55g or so. You will want the recirc skimmer's output close to the bottom but not right ontop of the input of the pump. The feed pump's ouput should be around the middle, where its at is fine, or you could go lower.

[dzeadow]

So, if I moved the intake of the recirc pump to basically almost the bottom, which in turn moved the output of the recirc to below the middle of the chamber that would be better? And since I've already got this sedra 3500 (350gph obviously) on order, maybe I could use that for the feed pump w/ a venturi on it which should reduce it's gph slightly right? And then get that Odyssea 500gph pump that you were talking about and use that as the recirc. Does this sound better?

Do you think a bubble plate spanning from the bottom left to right would be beneficial at all? It'd basically connect where the reaction chamber ends and turns into a return "tube"

[dzeadow]

I think I'm going to order the acrylic today, what size do you think is best? The Octo I have now is 3/16" and is pretty stout, I'm thinking the same would probably be good for this one as well. Also, does it matter if it's cast or extruded when dealing w/ skimmers?

[happyface888]

If I remember correctly cast is the nicer stuff because you wont get that hazy stuff while extruded you do. Doesn't the remora cup looks just like a rogues but the rogues you can't slid up and down? So basicly the same design and effective. well not effective for the remora though.

[luke33]

Pretty much happy, except the rogue's you can't take off like a remora. Cast is stronger and doesn't absorb as much water as extruded. Its better, but you pay for it. A bubble plate would be very good for one thing in this situation imo. You could have the feed pump feed the water to the bottom and the recirc pump could have its intake close to that, and the output would be right above that in the bubble plate seperate from one another. You would have to mount the pump differently though to have them so close to one another.

[happyface888]

any updates on how the skimmer will look now?

[dzeadow]

Alright, how's this look?



I put the intake for the recirc pump below the bubble plate just because I didn't know what was best, is it supposed to recirc bubble water or semi-bubble free water? If it's supposed to recirc bubble water, I'll adjust the intake just above the bubble plate and drop the bubble plate down a bit.
I can also raise the inlet/outlet tubes if it'll help. The reaction chamber is 10" right now just at the part where it's completely square to the top of the skimmer, so probably close to 5 or so inches to where I have the collection cup positioned in the drawing. I figured I should maximize the reaction chamber so I'll probably pull those pipes up more. That way they're right about 18" from the bottom of the skimmer to where they elbow in and out.

[dzeadow]

Ok, sorry for re-posting, but I fixed the drawing. I forgot to add a vertical wall going up further on the 2nd baffle, raised the collection cup and inlet/outlet tubes

[happyface888]

I was thinking after reviewing the design can water actually still exit? With the return tube all the way down wouldnt you have problems with the back pressure or something that wont let water escape as easily? I looked at other hob designs and the return outlet is near the top and never all the way to the bottom.

[dzeadow]

If you look at a lot of counter current designs, they usually have it set up like this to keep bubbles from exiting. As long as I have a T somewhere on the exit like our 100F's, I should be fine. Plus it's a 1" return tube w/ only a 1/2 inlet, it should be plenty big to handle the flow. I think I may also have to think about putting gate valves on the inlet and outlet to adjust height, but since the skimmer cup will be adjustable I don't think I'll have to.

[happyface888]

I'm just worried if the water can actually go up the exit tube. I havent seen a hob that has the exit tube reach that far down.

[dzeadow]

Water will flow through the path of least resistace, which will be the tube. Now if I put the outlet tube that went into the tank really far down in the tank, maybe i"d have an issue with back pressure. But I think I'm going to do the same thing I have on the 100F right now on it, but it'll actually be attached since I'll be working w/ standard pvc vs. metric.

[happyface888]

But the octopus doesnt have the inside return pipe that reaches all the way down though, maybe Im just not catching on