Bigger Overflow Holes 4/9/08
Hello Crew!
<Hello John.>
Thank you for all that you do. You are appreciated and admired by aquarists and fish everywhere!
<Thank you for the kind words and encouragement!>
I have one quick question. I have been reading, over and over, that in many instances, the diameter of the overflow holes on the A.G.A. MegaFlow systems [factory-ready] is not large enough.
<No, they are not really large enough.>
Can you/would you name a glass aquarium manufacturer, who makes standard-size/pre-drilled (reef-ready) tanks that have BIGGER diameter holes than those found in the A.G.A. tanks? I've done MANY web searches for this information, and I keep coming up empty.
<Most tank manufacturers will drill more/larger holes for you, for an extra fee of course. I have particularly found www.aqueonproducts.com (formerly AGA) to be great with their customer service. No long waits on the phone! Just give them a call and explain what you want, they will help you.>
Much appreciated. Have a great day.
John D.
<Welcome and thank you. Have a great day also, Scott V.>

Question about tank integrity re: drilling – 1/28/08
Dear Crew,
<Brian>
Hope all is well with you fine ladies and gentlemen. Once again, I find myself seeking the advice of the sea water sages. I know a few of you have prior tank building / fabricating experience, and wanted to run this by those who may have more experience than myself. I've drilled the back panel of my 75 gallon, which I believe is 3/8 inch glass, in preparation for the overflows to the sump, and intake and outputs for the closed loops. 6 holes in total, 5 are to accommodate 1.25 inch bulkheads, and one for a 1.5 inch bulkhead.
<Okay>
My question is re the integrity of the panel once filled with water.
I understand people drill their tanks all the time, and even I admit that the process was much easier than I thought it would be. However, I read many threads on various forums with people stating their tanks have failed usually with cracks radiating from near the location of the holes. I am wondering, would it would be advisable to silicone a few pieces of glass length wise to the back panel in order to provide stability, and reinforce the weakened panel? I was thinking of adding three strips to the back of the panel on the long dimension (48").
Will I gain any added stability to the panel by doing this? Or rather, a waste of time?
<Mmm, not an idea w/o merit... do look up the term "Euro-bracing" for ideas on how I would approach this>
I appreciate your input, and await your advice.
Cheers,
Brian
<Mmm, a few more statements, related... I encourage you to make sure there is no/little stress from the plumbing "hanging" from the through puts (VERY important) and that the bulkheads themselves are well seated (with a smear of Silastic on the inside and outside faces, including on the gaskets) and that these are securely tightened... once again, to distribute the force about their perimeters... Bob Fenner>

Re: Question about tank integrity re: drilling   1/28/08
Bob,
<Brian>
Thank you for the swift reply. After researching "euro bracing", I've decided that it would indeed be in my best interest to beef up the
integrity of the tank. Will take the suggestion to heart, and visit the local plate glass shop for some reinforcing strips.
<Ah, good>
Also, I wanted to thank you personally, Bob. When I was new to the hobby and wandered into my LFS to purchase a tank and some fish a few years ago, after speaking with me for a few moments, the clerk told me that there was only one piece of equipment I would need to start with.
He then proceeded to walk me over to the hobby literature section, pick up a copy of "The Conscientious Marine Aquarist", and advised me to go home and read it over several times, then come back when I was ready to go. To this day, I still find myself referring to it for
advice and guidance. Both I, and my reefs inhabitants thank you.
<Welcome my friend>
Next time you're in Chesapeake Bay country, drop me a line and the beer and crab cakes are on me!
<Mmm, yummy!>
Kindly,
Brian Rinehart
<BobF>
 

Re: James, flow rates through plumbing, fittings   11/13/07 OK, bottom line is...the calculators are in err, and the manufacturers of the HOB overflows are fibbing about the 600gph flow rate. Also, when you say the only way you would get that flow rate is by siphoning. Isn't that what the HOB's are actually doing with the "U" tubes? <Yes! Again... much more water to be had via siphoning... but the downsides of... what happens if the siphon/s stop? The issue of transit volume...> Anyway, I must find a more reliable source for calculating such. So goes answering plumbing queries for now.. do not want to look like an ass doing so, for sure. James <The construction, presentation of such "tables", inherent difficulties in explaining their limitations to users is why I/we've chosen not to even present such... You and I can only guess the number of wet floors, shorted electrics, dead livestock... frustration and consternation of hobbyists from such "data". Cheers, BobF> Re: James, flow rates through plumbing, fittings   11/13/07 OK, I see I have a message in my inbox from the querior. I think I'll tell him my wife is answering this because I passed away yesterday. <Heee! You can only use this one time...> In looking at plumbing calculations on the web, I do see there is much involved, one notably is friction. <Yes... induced drag is a huge factor... I have seen systems where the latitudinal "runs" from lines in the backs of large tanks were very long... there was/is NO way that water was going to get magically "sucked" down these...> Depending on the product being used, <?> friction can decrease flow rates of course. So now I'm thinking the ribbed hose connecting from bulkhead to bulkhead would rank high on the list because of all the ribs present, but probably no where near as bad as direct plumbing using elbows and such. <Oh! Interesting... Well, not much... inside diameter is inside diameter... the ribbing is outside this measure> This job is going to drive me nuts. Have a good day. James (I too, take blood pressure medication, Ziac. I thought this was suppose to be a relaxing hobby. <I use (don't laugh) black flaxseed and 10 mg. of Norvasc daily... Cheers, BobF> Overflow rates... again.  11/13/07 My flow meter data shows a 1" bulkhead flowing right at 300 gph in a best case scenario. With much plumbing it was more in the neighborhood of 270-280. I used to think they flowed more too!! I plan on confirming the flow meter rates with time vs. volume displaced tests. I will write these up and sent it to you this weekend. Talk soon, Scott V. <Thank you for this input Scott... Am STILL dreaming of that "Aquarium Engineering" book by you and Eric Russell... and I know just the excellent editor that should oversee this project. Am cc'ing James Lawrence (Microcosm) here. James... it's way past time for an update, bettered tome than Pete Escobar's on the topic... What say you? I will gladly help with review of lighting, aquarium and stand, electrical, plumbing... sections. BobF>

Plumbing Nightmare… (Indeed!) – 12/07/07
Dear Mr. Fenner,
<<Hiya Jerry...EricR with you today...>>
Why is it the more I read on your website, the more money it costs me to fix the errors!! Yes I know shoulda, woulda, coulda!!
<<Ah yes! But think of all the learning experiences/opportunities that have come from it>>
I upgraded my tank 4 months ago and was so excited about the upgrade I didn’t really check the stats on the overflow.
<<Uh-oh...I sense a “Mega” mistake coming>>
Right now I have a 90g reef with a MegaFlow unit,
<<Yes, well...try not to giggle when you say that [grin]>>
1” Drain Pipe and ¾” return, which now seems fairly small.
<<Mmm, yes...and as Tom Hanks stated when the “Wonders” fell apart after a single hit song...”A very common tale.” We are well aware of/often hear about these tanks and their shortcomings re the advertised “Mega” throughputs>>
The drain pipe drops into a sump w/ trickle plate/Poly-Filter, bio-balls replaced with DSB/live rock, no lights.
<<Okay>>
Second chamber holds my AquaC Urchin-Pro and a Rio that pumps into a 20g refugium, from there it returns via a 2400 Mag-Drive, reduced to ¾”.
<<Okay...a couple red flags here. First- Pumping from the wet-dry to the refugium and the pumping from the refugium to the tank is just a plain bad idea... Even if you use valves to balance flow/were to use identical pumps, this “balancing act” just doesn’t work due to variable differences in head pressure/line resistance from the buildup of bio-matter. Sooner or later an imbalance “will occur” likely resulting in water on the floor, damaged equipment, even the possibility of fire or electrocution. You really need to position the wet-dry such that a “gravity” overflow of sufficient size will supply water to the refugium for return to the display. Second- That 1” drain is only going to handle about 300gph. Assuming zero headloss for the moment from the Mag-Drive, that pump is twelve-times more pump than you need! And no doubt these issues have something to do with you writing in...[grin]>>
The problem is a few-fold!!
<<Yes>>
You state in your plumbing article that you should never pump one box to the next, and that it is destined for disaster.
<<Indeed>>
Trust me I have spent countless nights wondering when one pump will go out, and because of one bad pump loss two. (and the constant adjustments!!)
<<Yep...Murphy’s Law “will” catch up to you>>
Also you state that Skimmer and refugium should get raw water,
<<Ideally>>
and flow through the refugium should be handfuls.
<<Hmm...this, in “my” opinion, is variable...and often dependent on the type of refugium methodology employed. But for the most part, yes, a circulation of a couple to few volumes of water per hour will usually suit>>
Here is my plan; since I just bought a new AquaMedic Ozonizer (got a great deal or I would have bought the Sanders) and I am waiting for my ORP controller and new EV120. I figure since I have to make changes anyways, I might as well make them all.
<<Excellent>>
Promise I am getting to the question!!
<<No worries...does help me to have all the info/know the background>>
Since drilling is not an option and a hang on back overflow will not fit, here is my new plan.
<<So, limited to the existing throughputs, eh…you can “make do” re circulation to the sump/refugium…but you will definitely need to provide some supplemental water flow within the tank via powerheads>>
I was thinking of taking the return line and making it into a second overflow, since you say it is better to have two than one.
<<Some redundancy is good, indeed…but this is most often done with these so-called Mega-Flow tanks simply because the supplied throughputs are just too inadequate>>
The 1” dropping into the sump (DSB/Live rock will be removed and put into the refugium with the other), the EV-120 in the fist chamber with raw water and the second chamber will hold both pumps.
<<Let me stop you right here for a moment… “Both pumps?!” Even with utilizing both the 1” and ¾” throughputs as drains, you are still only looking at a maximum “gravity” flow rate of about 450-500 gph… You only need a pump that will supply from 700-900 gph; to allow for head-loss and gradual loss of flow from bio-film buildup in the plumbing. Also, do be sure to plumb a gate-valve “after” the pump to allow you to throttle-back this flow if/as needed>>
Mag 2400 will be piped 1” (or ¾” what do you think is better?)
<<I think a smaller pump “is better”…with no need to exceed the diameter of the pipe beyond that of the pump outlet>>
behind the tank, dropping in by split Loc-lines.
<<You will likely find that only a single return will supply enough “force” with the limited water flow to be useful>>
I figure with 4 elbows and 4’ of upward pump, collective maybe 9’ of headspace. Mag 2400 will now return maybe 1250gph.
<<Maybe so…but still way more than your drains can handle>>
The ¾” will drain into the refugium, so now both skimmer and refugium will get raw water.
<<This is good…and hopefully the refugium then “gravity drains” to the pump chamber of the sump>>
Rio 1400 returns to a ¾” SeaSwirl.
<<Save your money here…you just don’t have the overflow/drain capacity for it>>
Whew!! I was thinking that this addresses all the issues that you have written about.
<<But unless I have grossly misunderstood or something has been misstated, your resolutions are flawed>>
But then I was thinking, will the overflow wall allow enough water in or will it suck dry?
<<The “overflow wall” will not be an issue, the drains will simply not handle this much water volume>>
You say gravity is something you can rely on, so since I am pumping more back in, won’t the overflow box fill just as fast?
<<The box will fill, yes, and overflow… And gravity is indeed the issue here. Because you can pump a certain volume of water through a specified diameter of pipe does not mean that same volume will “gravity drain” through the same diameter…is not the same hydrodynamics. You can not drain the volume of water from this tank that you are indicating without increasing the number or size of the throughputs. Since you say this is not possible, your only option is to reduce the volume of water returned to the tank>>
And if the box is overwhelmed with how much I am pulling out, is there a way to speed up the amount flowing in? Maybe cut bigger and deeper grooves on the top?
<<Again…I think the overflow box is the least of your concerns here>>
Well anyways before I start ripping things out and buying new parts I thought I would run this past you.
<<I’m very glad you did>>
Your views and suggestions would be greatly appreciated. Since you started this whole thing anyways!! I would have been perfectly fine sitting in ignorance!!
<<Mmm…not for long…>>
Have an awesome night and if I haven’t said it yet, you guys are the absolute best on the web and anywhere else!!
<<Thank you…a collective effort>>
Thanks,
Jerry
<<Jerry… Please write me back to let me know your thoughts/understanding of what I have stated, along with anything you have already done and the results re (have you run this tank lately?). I do think this matter likely bears further discussion. Regards, Eric Russell>>

Re: New Tank And How... less/more on through puts, flow rates...  12/4/07
They designed it all
I have 2 x 1 inch drains with elbows.
I have 2 x Aqua Euro return pumps with 1200 to 1400gph each so 2400 to 2800 return.
They say 1inch drain should handle 1200gph. Is this not true?
<Well, lets put it this way, I'm running a Little Giant circulation pump that puts out
about 1000gph with my three foot head, have no elbows in my drain line, and I have to throttle the pump down about 20%. I'd ask Tenecor if they tried the system out before they sent it out to you. I might ask one question...are the drains tied together into a "T"?. James (Salty Dog)> <<Mmmm, ummm, none of the above... the one inch lines in an ideal universe can/will handle no more than about 300 gph... unless they're (dangerously) operating as siphons... Time to read... and consider adding more holes/drain lines or routing out the present ones to at least 1 1/2" ID fittings... Start here (both James and the querier):  http://wetwebmedia.com/marsetupindex2.htm
The fourth (pink) tray down. RMF>>

85 gallon hex mixed reef - should I continue? Drilling holes mostly   7/27/07
Hello to all,
<Hi there>
I've been searching here (great info!) and various other sites for awhile now, and can't find many relevant posts to confirm my plan before I continue. I'll try to describe my overall plan and then ask for your thoughts on a few specifics.
<Okay>
I picked up a used 85 gal (Oceanic?) hex glass tank (~16" each side x 30" deep) and stand a few years back on the cheap with the intent of a mixed reef tank. Original plans were for a unique viewable-on-all-sides design with centrally located overflow/return to a remote sump. A custom central (probably circular)
<Consider sleeving this... to move water from the lower level...>
overflow will be at the top surface with water draining down two 1" Durso pipes
<Mmm, too small... make this one two inch...>
to a remote sump. The sump will have standard refugium, skimmer, Kalk drip, external return pump, etc. The return will flow up from the bottom of the tank, 180 back down into the middle (with a siphon break hole)
<Mmmm>
then split to multiple outlets along the depth of the tank. The tank is to have a 4-6" DSB with LR stacked/attached in a cone shape mostly full-height to the vertical drain/return pipes up to the bottom of the overflow. I know hex tanks don't offer ideal surface area, but hope the sump/skimmer will mitigate this.
<Unless power, circulation fail...>
Shooting for 20-30x turnover so I can handle some SPS at the upper level and Softies down lower and just a few small fish with a single 250W MH and supplemental 24" T5's.
First problem - Without adequate research beforehand, I had three holes drilled for 1" bulkhead fittings in the center of the tank (two for drains, one for return). My hope was to supply all the tank flow requirements through these, but checking some of the calculators looks like the most I can get is about 1700 gpm (with 26" of overflow length - maybe a custom 8" dia overflow).
<Not even close to this...>
Any thoughts on maximizing flow with this setup or any visually unobtrusive powerheads to make up the difference?
<I'd start again... have the tank re-drilled>
Second problem - Being an older tank, I plan to reseal all the joints.
<I'd reconsider this... a big job to cut away, clean all, separate the glass... likely the re-do will be less secure than the present... Cheaper by far time-wise to just buy a new tank...>
Before I go through the hassle of resealing, do you think the three holes in the center of the bottom have compromised the strength too much to handle the weight of water/rock/sand (the ligaments between the holes are ~2", the bottom is 24" wide face-to-face)? Would laying a piece of ½-3/4" HDPE on the bottom prior to stacking help out?
<Maybe... better to repair/seal a piece of glass over all, inside and one outside... and start again as stated...>
Thanks for all your valuable information already posted & any comments on these two issues and any other insights is greatly appreciated.
Regards,
Michael Johnson
<I do wish we had chatted afore... Please think this project over for a week or so... before doing much else. Bob Fenner>

Need help with a tank stand--can't tighten bottom bulkheads due to wood center brace  6/20/07
Hi there,
I'm hoping you can help me. I have a Perfecto 150-gallon glass aquarium whose dimensions are: 48" long, 24" wide and 30" tall. The tank has plastic center braces on the top and bottom. The stand for the tank is wood and supports it fully around all edges; the top is fully open but with a wood center brace running vertically through the center.
Recently I had the tank sent out to an aquarium company to have the glass bottom drilled for two bulkheads along with an internal overflow box installed. I just got the tank back today, and they did a beautiful job. However, when the tank was set back on its stand, the wood center brace on the stand was too wide to allow me to fully tighten the bulkheads underneath.
<Doh!>
I asked the company who did the work what I could do to rectify this--they said I could notch a cutout in either side of the wood center brace to accommodate the bulkhead fittings.
<Mmmm>
However, I'm worried that this will compromise the integrity of the stand--
<Yes>
I don't want it collapsing and spilling 150 gallons of water on the floor. Could you guys help me out as to what I should do--should I consult with an engineer first or is it okay to do this modification?
Any advice would be greatly appreciated. Thank you.
<Well... likely a "thinner" nut can be found... or the through-hull/bulkhead fitting reversed (with the throat up, perhaps shaved, cut down...) and an extra gasket found for both sides... and a smear of Silastic on both sides... that will do here... Perhaps with some shaving of the wood twixt the tank and stand to accommodate... If push comes to proverbial shove, you might need to consider adhering the (likely PVC) fitting directly onto the tanks glass... and dedicating yourself to never jarring it... Otherwise, the worst... giving up on the present holes, sealing over them (with glass panel/s and Silastic) and having the tank re-drilled. I agree with your NOT cutting through the manufactured stand support... UNLESS you feel comfortable (YOU!) with replacing this support (and losing the manufacturer's warrantee) with two new ones, placed on either side... Which is really what I'd do... Cheers, BobF>

Re: Need help with a tank stand--can't tighten bottom bulkheads due to wood center brace   6/21/07
Wow! Thanks so much, Bob, for your kind reply!! I really loved your book, by the way; it really helped me get started with my tank! Plus I've learned so much by reading through all the articles and FAQ's from WetWeb Media; you guys are great! I think I've come up with a plan for my stand. I'd really rather not mess around with the bulkheads; I only really need to notch the wood 1/4" on either side, but leave the center brace in place, and I think I'll place two new boards on either side, like you advised. I really don't want to have the tank re-drilled: it took the company forever to get the work done; I'd consider getting a new stand before doing that. Anyway, thank you so much, Bob, you've really helped me out!
<Ah, good! Cheers, BobF>

Request for Enlightenment from the Crew – 06/14/07
Hello Crew:
<Uhh, Dan>
First and foremost thank you so much for this website. The information here is fantastic, I can’t stop reading and my wife is getting irritated because I’m spending most of my evenings at WWM.
<Heeeeeee! That's not "on", but "at"! Wow!>
I keep telling her that at least it’s better than the local bar!
<And cheaper and easier on your liver!>
Anyway here goes, I just purchased a 100-gallon rectangular tank (60”x18x24) and requested that the internal overflow be placed in the back left corner of the tank. When the tank arrived I noticed that the overflow drain hole could only accommodate a single 1” bulkhead (hole size is 1.75”).
<Bunk!>
The LFS is recommending a Mag 12 that will have to pump a little less than 5’ high and I plan on splitting the return so that the returns are from each side of the corner overflow. I’m guessing that the flow rate will be around 1,000 gph. From what I read on your site that a 1” overflow can handle 600 gph maximum and is better at 300 gph,
<This last is likely the maximum... You need larger holeS... plural>
I brought this to the attention of the LFS. They told me that they have used this set up before and it will be fine.
<Mmm, no. They're wrong or at least not understanding... or maybe I'm a butterfly dreaming I'm a human pet-fish kind of guy not understanding... and will wake up and be a real Reef Ready marine system... Wait, no... I AM a pet-fish kind of guy and am just confusing the situation. They're wrong>
(Their other solution is to install a smaller pump,
<Uhh, Dan... no>
which I do not think is a viable due to the very low turnover rate that would be required.) They have also recommended 2 Tek retro fit T5s (4 bulbs), a Euro Reef RS135 and a 40 gallon sump. Your wisdom please!
<Nyuk nyuk, nyuk. Wise guy eh?>
Thanks,
Dan W. - California
<I'd go with this skimmer... keep looking around for the lights... have someone from the shop come out and drill two 2 1/2 " OD holes for use here (one over the existing if you'd like) and not both at the same level necessarily... And read here: http://www.wetwebmedia.com/marsetupindex2.htm
"That'll be very... time consuming"... Mr. Deets in "Beetlejuice". BobF>

Moving sump to basement, Increasing Bulkhead Size/Plumbing a Skimmer and Chiller - 04/15/07
Hello Crew,
<<Hi Jerry>>
Thanks for your help in the past on lighting, now I could use your help on planning plumbing.
<<Let's see what we can do>>
I want to move my sump, skimmer and pump (and new chiller) in the basement.
<<Ok>>
It would run through wall with 2x4 studs and 2x4 plates which limits pipes to 1.5 or less.  My current 110 acrylic reef tank has overflow 1" and 3/4 return with Little Giant 4 pump.  Can the 1" be enlarged with Roto-Zip or Dremel tool or a file to accommodate a 2" bulkhead?
<<It can (using the Roto/Dremel tool), or even with an appropriately sized hole saw like those meant for cutting holes in wood (the "bi-metal" blades work the best IMO)>>
Will the 3/4 return be enough for GenX Mak 4 (1200gph) after 12' lift and split for chiller and skimmer?
<<It will, though I would increase this to 1", since you're re-cutting new holes anyway.  Also, I don't recommend "splitting" the pump to feed the skimmer and chiller.  This sort of "balancing act" just doesn’t work.  It's not so much an issue with the chiller, but you will find yourself having to constantly fiddle with the skimmer to keep it "tuned" due to the almost constant variations in flow because of fluctuating fluid dynamics…best to use a dedicated pump for the skimmer in my opinion>>
Would you recommend turning both bulkheads into overflow to sump and return over the tank?
<<Since the sump will be located remote from the display/out of the living area and if your intent is to maximize flow through the sump to reduce the need for ancillary water flow devices...absolutely>>
Thanks so much,
Jerry
<<Happy to assist.  EricR>>

Bulkhead Location - 04/11/07
Hello,
<<Greetings>>
I wrote to you about two years ago when I was planning to set up my Mediterranean aquarium (I'm in Italy).  You were very helpful and I'm happy to say that my tank looks great and is very healthy on its second birthday!
<<Ah...very nice to know>>
I am now planning to replace it with a larger aquarium which a glazier is going to cut and silicone for me.  The measurements are (in inches) 36 long by 16 wide by 20 tall.  It will have a DSB and a Remora backpack skimmer which I plan to place in the sump (bucket).
<<I see>>
My questions are these:  does drilling a one-inch hole in the back of the tank compromise the strength of the aquarium more than if the hole were drilled on the side?
<<Not at all...the “compromise,” if any, would come from its placement in regards to the edges/seals of the tank>>
Does it make any difference if the hole is in a corner or in the center?
<<Either is suitable...as long as sufficient distance is maintained from the edges of the panels.  A good rule of thumb in my opinion is to drill the holes such that, the edges of the hole are no closer to the edges of the panel, than a distance equal to the diameter of the hole...so the bigger the hole, the greater the distance.  In other words...if you drill a 1 7/8” diameter hole for a 1” bulkhead fitting, the edges of the hole would be at least 1 7/8” from the nearest panel edge>>
In your opinion, is it better to make the hole close to the waterline with a horizontal tube and basket or make the hole lower down in the aquarium and connect an "L" tube which can be adjusted for height to achieve the desired water level?
<<Again either is suitable (I use the latter method on my tank)...as long as you maintain sufficient distance from the panel edge when drilling the hole>>
There will be only one hole for the overflow and the return will be over the top edge with a closed loop manifold (thanks for such a great idea!).  My husband is much less enthusiastic than I am about aquariums so I'm only getting one chance to plan and build this tank correctly...since this is not an overflow device used by any of my Med-forum friends, I wanted to check with you to reassure myself that I'm making intelligent choices.
<<Understood>>
Thanks so much for your help and your amazing website!
Eileen
<<Is our pleasure to share.  Eric Russell>>

Pump question for Aquavim tank... Not Reef Ready- 03/25/07
Hello guys!
I recently purchased an Aquavim 88 gallon seamless RR
<http://www.aquavim.com/ rounded glass...>
tank setup.  It's an awesome attention-getter in my living room, but I'm getting frustrated trying to figure out a circulation/pump plan for this very tall tank/stand.  I'm calculating a head pressure of about 5.5 feet.(4.5 feet from sump to top of overflow box, then a 90 degree turn, then a 45 degree turn into tank).  It has a single 1" outflow, then a 3/4" return. (I know, the 1" return is killing me!)  
<As will the 3/4" return... Not RR... Reef Ready>
It seems like I'm in between pump sizes for my planned FOWLR setup with Orca sump refuge.  For example, the mag 7 puts me around 400-420 gph which is 4.6 turnovers.
<The 1" return may not fit this...>
Moreover, the mag 7 only has a 1/2" outlet so I would lose even more head pressure going up to a 3/4" return.
<Not much... I wouldn't be concerned here>
The Mag 9.5 would be around 720-750. (Too much for a 1" return).
<Way>
   The pump has to be the submersible type as I don't have a bulkhead for the return.
<I'd cut, fit one... or switch sumps to this...>
I could go with a mag 7 and do powerheads in-tank, but this is ugly amongst the other issues.  Could I valve-down a Mag 9.5??
<Could...>
Is this safe??
<Is, but I wouldn't...>
  What would you do??
<Try to see what sort of flow you can get through both the present through-puts... and loop the discharge, return from whatever pump you settle on to over the top... on/with some sort of "closed loop" arrangement... this pre-drilled tank is not really able to be used for the intended purpose...>
Any other pump brand or suggestions that would get me closer to 500 gph without having to deal with valves??
Thanks guys!!
Kris K
<As stated... and posted. Read here: http://www.wetwebmedia.com/marsetupindex2.htm
It's... an education.
Bob Fenner>

Drilling a 120-gallon Aquarium on 18" Side   2/14/07
Hi,
<Paul>
Sorry about the previous blank email; hit the wrong button.
<Ahh, another mystery solved>
I really enjoy your forum and appreciate the last assistance you provided about the seam on my new aquarium.  I would now like to drill it for overflow and a closed-loop system. (Aughh, not another drilling question)  I am using the aquarium as a room divider so it will be seen on three sides (the two long and one short, obviously, I guess).  So I will only be able to drill on the one short end.  The tank dimensions are 60" X  18" X 24".  The glass is 3/8" thick.  I would like to drill three 2- 3/8" (60 mm) holes to allow for 1.5" bulkheads.
<Sounds good>
  I want to use 2 of the bulkheads for outlets to the sump and use the third for supplying the closed-loop.  Most recommendations I can find suggest putting the bulkheads as high as possible.  Would 3 of these holes drilled in a row along the upper part of the 18" side be too many?
<Should be fine... I'd allow a "couple" of inches of glass above each hole.>
I'm concerned about weakening the side too much.  There would be about 2.75" between the holes and 2.75" in from each side.  If this is too many holes, should I just use two holes, one for the return and one for the CL.  Or perhaps two in a row and one a bit lower?  
<I would go with the three you list... spaced as you state... Have you given much thought as to how you'll arrange the return discharge/s?>
Thanks again and in advance for your help!
Paul H.
<BobF>

Bulkheads And Flow - 08/07/05
Dear Eric,
I promise this is the last time I'll bother you.
<<Hello again Andrew...no bother...really...I'm happy to try to assist.>>
But I was thinking about it and thought that (2) 1.5" bulkheads would/could give me around 1000gph. (Please correct me if I'm wrong)
<<If you're talking about both draining to the sump, then yes, is quite plausible.  Though I must say, that is an awful lot of water to process through a sump on such a small tank (30g)...the slightest restriction is going to put water on the floor in a hurry.  Not to mention the NOISE it is going to make.  I would recommend using one bulkhead to drain to the sump in conjunction with a smaller pump (say a MAG 5), and use the other bulkhead to feed a closed-loop with another MAG 5 or even a MAG 7.>>
I was planning on running a Mag Drive MD9.5.  I calculated that this would give me about 800gph at 4.5' head.  Is that to much to run through a sump?
<<Ah, should read ahead <G>...>>
I wasn't planning on having a large sump, maybe 10-20 gallons and a separate 10 gallon Plenum.  I was planning on running the return into a manifold and was wondering if I should stick with the 1" bulkheads and run a smaller pump and drill a third 1" bulkhead
to run closed loop.  I would only do this if I had no other choice about the sump.
<<Now you're talkin'...  Here's my recommendation for the simplest, most manageable configuration in my opinion.  Have three holes drilled for 1" bulkheads...Use two bulkheads to drain to the sump with a MAG 7 return pump.  Use the third bulkhead to feed a closed loop with another MAG 7 pump.  With head loss due to height/plumbing, you'll have a total flow rate of around 600-700 gph I'm guessing.  By using "two" 1" overflows you will be able to increase the pump size a bit (MAG 9.5) if you determine you need/want the extra flow.  Also...if given the choice...go with the 20 gallon tank for your sump...you need to ensure you will have enough "empty space" to handle the drain-down from the display tank in the advent of a power outage.>>
It will only contain a skimmer, a little mechanical filtration, and a little chemical.  <<and your pumps>>  Will this be overloaded?
<<Assuming you go with the larger of the two sump choices (20g), should be fine.>>
Thanks Again (and again and again...)
Andrew
<<My pleasure my friend, EricR>>

Need increased drainage flow to keep up with pump... Small holes really don't 7/7/06
Hi, I just started plumbing a 75g reef-ready tank with a corner overflow and 1" bulkheads drilled on the bottom of the tank.
<... need to be bigger, larger diameter...>
  The filter I plan on setting up with this tank will be a EcoSystem mud-filter which requires 800 gph to run effectively for a 75g aquarium.
<Mmm, could/can be run on less... with other filtration, circulation provided otherwise>
The pump I bought is a CA-4000 submersible pump which puts out over 1100 gph at 0' of head and around 800 gph at 3 1/2' of head which is how I have it connected currently.  My problem is that the overflow drain cannot keep up with the pump and the pump begins to pump half air half water after only a few minute of the system being turned on.
<Yep>
I've researched and found that the max flow through a 1" bulkhead is around 600 gph so most likely that is my problem.
<Agreed>
Is there any way to increase the drainage flow without drilling a larger hole for a larger bulkhead?
<...? Mmm... well, no... you need to either add flow elsewise or re-drill... Please read here: http://www.wetwebmedia.com/pbholesfaqs.htm
and the linked files above. Bob Fenner>

Using Old Rock/Drilling Bulkheads - 08/27/06
Hey guys,
<<Hello (but don't forget the very capable ladies here as well)>>
Thanks again for your time and dedication to our hobby!
<<Is an honor/pleasure to help>>  
I have 2 issues I need help with:
<<Alrighty>>
First, I have read thru the LR section in depth and could not find an exact match to my problem.  I recently purchased a used, and neglected 120 gallon that housed a single clown grouper with several large pieces of rock (it was a FO with rock??).
<<Indeed...that would be a FOWLR (Fish Only With Live Rock)>>
I have kept the rock wet for a few days and can see a few small life forms on it (actual moving little white/clear bug things).
<<Amphipods...probably>>
The rock looks terrible as the tank was neglected and the rock is all dark brown and black.  I will be setting this tank up as a FOWLR and I am thinking that I would like to start over with the rock.  Letting it dry and cleaning it somehow and then letting it cure in the tank for a month or two before adding new fish (pending testing results).
<<Mmm...letting the rock "dry out" will negate its benefits...why not simply keep the rock as it is?  If the color is an issue, it will likely change with improved water quality/lighting>>
Can I get the rock to look better?
<<Depends on what you consider is "better">>
Is it worth losing whatever life it has on it?
<<Not in my opinion>>
It was not really a traditional live rock,
<<...???>>
it has life but it looks very bad.  They are great sized pieces.  The substrate is crushed coral, I would like to reuse it.  It also has black and brown staining on it.
<<This is most likely forms of algae, and will "change" with changes to the environment, as stated>>
Can this also be cleaned?  If so how?
<<Swirling/rinsing with clean saltwater will do the least damage, though you will still loose some biota>>
I don't mind starting over on the rock but will my cleaning methods effect any future fish or possible changes to inverts/coral down the road if I go that direction?
<<Indeed it will...you could give the rock a rinse and a "light" brushing with a soft-bristle brush, or replace it (entirely or in portions) with fresh live rock>>
Second, the tank is a traditional (non RR) tank.  It came with a sump/wet-dry and a HOT overflow.  I am weary of the overflow as I hear that they will eventually fail.
<<Is a good chance, yes...but this risk can be lessened a great deal by employing a redundant system (two siphon overflow boxes) with the first>>
I have once again read on WWM about tank drilling and am thoroughly confused by all the different opinions and issues.
<<Let's see if I can help un-confuse you>>
I would like to drill the rear for 2 sump supplies and 2 sump returns.  Where exactly (how far down and over/apart) do you recommend?
<<Well, if you've established the back glass in non-tempered, I recommend you place the throughputs the width of the hole-to-be-drilled from the edges of the tank, and no closer re to any other throughputs...clear as mud?  For example...a heavy duty 1.5" bulkhead requires a 2.6" hole...the edge of the hole should be no closer than 2.6" from any edge of the tank, or from any edge of another bulkhead hole.  Adjustment of water height in the tank can be accomplished with elbows to raise the level of the pipe outside the tank, or used as adjustable "overflows" within the tank>>
Also what size is best for this size tank if I use a strainer for the supplies down and a directional elbow for the return up?
<<Two 1.5" bulkheads for the drains, and one or two .75" or 1" bulkheads for the returns...or you can simply plumb the returns over the back/ends of the tank>>
Should both the supply and the return have a T installed before the sump?
<<For what purpose?...in what configuration?>>
Also, are there and tips for drilling?
<<Indeed, yes...have a read here:  http://www.wetwebmedia.com/pbholesfaqs.htm >>
I have seen a tank drilled before and they used cooking oil for the lubricant while cutting?  Is this OK?
<<I've always just used water for lubricating the drill bit...works well and is easy to clean up>>
I plan on ordering the needed bits online, any recommended sources?
<<Several choices about...I bought my last bit here: http://www.diamond-drill-bit-and-tool.com/Diamond-Drill/MAIN.htm >>
Any tips?  
<<Heat is your enemy...follow the recommended rotation speed for the size core drill bit used.  The manufacturer states these bits can be used "dry", but use of a lubricant (water) will keep heat down, greatly extend the life of the bit, and speed the drilling process...I use simple 'Play-Dough' to create a "damn" around the area to be drilled and fill/refill with water as needed while drilling.  Also, when possible, use of a drill-press or drill-jig to keep the bit vertical to the glass surface will lessen the chance of damage/fracture of the panel>>
Thanks once again for your help and contribution to our obsession!!!
Randy
<<Quite welcome.  Regards, EricR>>

Pump Size and Overflows
Dear Bob and Crew,
<Scott F. your Crew member today>
How do you guys rate the Mag Drive pumps in  terms of reliability?
<I find the new Mag Drive pumps to be quite reliable>
I was thinking of getting the MD24 for a 75 gallon with 55 gallon sump. I was hoping 4, 1" bulkheads could handle 1900 gph. Do you think I'll be ok?
<I think that they will, <<No... RMF>> but with little margin. You may want to go for 1.5" overflows to be safe. Regards, Scott F> <<Yep... RMF>>

Overflows
Hey guys!
I have a custom tank in the plans. Its a 125 gallon. Dimensions are 60LX24DX20H. My LFS is having it built and drilled. I do not know much about how big or where to drill so I was relying on them for information. Before I went through it, I wanted to run what they told me to you guys to see what you thought. They recommended that I have 1 drill in the center of the back wall. It will have the wall thing built around it (don't know what it is called, but it has the groves in the top for the water to flow through). 
<An overflow "tower" or raceway. Not necessary if drilled through the back... you can use commercially made thread in screens instead>
Should the holes be in the back or on the bottom of the tank?
<Almost always in the back>
This (wall) will have these grooves on three sides. I was wondering if it would be better to have 2 holes drilled, one in each back corner but being in the corner, each would only have 2 sides of the grove things. I would also appreciate an opinion for a pump. I want a good one so I was thinking about Iwaki. but unsure of how much pump I need. Thank you for any information you can shed on my situation.  Rob
<Rob, your answers and much other needed input on these matters is archived on our site: www.WetWebMedia.com Go there, use the search tool, or better, peruse the setup area of the marine section. Bob Fenner>

Bulkhead Diameter
Hi Guys-
<Hey there! Scott F. your guy tonight!>
I have just purchased a new pump, Amp Master 3000, and am worried about the necessary size for the return piping to the sump. I currently have one overflow box in the back corner with a 1.125 ID bulkhead (using a Durso standpipe to keep things quiet). In order to handle the 3000 gallons per hour, I am having another overflow box installed in the other back corner, but not sure of the size piping that I need. I am certainly not an engineer, but found some gravity flow equations on the web that gave me an overall minimum ID of about 2" taking into account the 3 foot vertical drop and 3 foot horizontal length to the sump. Does this sound about right to you?
<Yep. I'd go with 2 inch standpipes for this type of flow>
Therefore, would a 1.5 inch new bulkhead be enough with the current 1.125" in the other corner, or should I go larger? Thanks for all your help, Steve
<Larger cannot hurt, but I believe that 2" would be the way to go! Regards, Scott F.> 

- Overflow Size -
Hello everyone. <Hello.> I have a quick question. I would have posted in the forum but it appears to be down right now. I have upgraded my pump to a Quiet One 6000 and have put all the pumping into place. I have a 55G tank and a 10G sump. Now I was wondering what size of an overflow would I need? I currently have a H.O.T overflow box with a 1" and 1 1/2" U tubes to move the water between the boxes. I have a 1" drain hose in the back box. I currently have to use a ball valve to throttle back the pump because my drain can not move enough water. My current box is 5" across 7" deep and 3" thick. I was wondering if I increase the drain from 1" to 1 1/2" would that be enough? <Yes, that would make a big difference.> I am currently looking at building an overflow setup that is 15"x8"x4" and using either a 1 1/2" drain or two 1" drains. <Either would be adequate, but you also might to think about two overflow boxes which will give you the right amount of drainage and also redundancy should one of the two develop problems.> I will be using two 1 1/2" U tubes to move the water between the boxes. Could you give me your ideal on how many drains I would need and what size. <Two overflow boxes, each with a 1.5" bulkhead would be perfect.>
Oh and the pump will be moving about 943GPH with my current plumping. Thanks.
<Cheers, J -- >

- Bulkheads -
Hi Guys,
I am starting a 180 gal. reef. My two corner overflow are 2". Last time I wrote I was having problems with water draining fast enough. So a added two 1 1/2" bulkhead on the back wall of the tank and two 1". My two pumps equal to 5100 gal. /hr. Now when I turn the pumps on I hear a loud sucking noise from the 2" overflow. Do I still need to add more bulkheads? <No... the sucking sound is just what happens when you have a large amount of water passing through them... air is being pulled down with the water.> I want to avoid dialing back the pumps since water entering the tank goes thru a manifold. My tank is still in the testing stages so I am flexible. Also what is the typical flow rating on these bulk heads? <A one inch fitting should be able to move 1500 GPH peak... reality will be somewhat less. A 1.5" bulkhead should be able to handle about 2500 GPH max.> What would the proper size sump be on a tank this size? <As large as possible - you've got a lot of water in transit and you'll need room to have a working sump and somewhere for the transit volume to go when the power shuts off.>
Thanks for you dedication to this site.
Sincerely
Stephan
<Cheers, J -- >

Max drain in a 1.75" bulkhead?
Hello to the WWM crew! << Blundell here. >>
Although I am sure this info is somewhere in your archives I had no luck locating it so here we go.
     My 80 AGA RR has a single bulkhead in the bottom of the overflow box.  The inside of this bulkhead is 1.75" wide and the outside is 2.4" wide. << That is big. >> I need to know the max GPH I can run through this so I don't purchase too large of a pump.  I am currently looking at the sequence Reeflo dart which would run about 2700 gph @ 4 foot head. << I bet it can handle that.  I'd try it out, that is really the only way to know. >> What is the max gph I can swing with this bulkhead?  Should I consider a second closed loop pump on a separate manifold (I currently am running a mak4 (1180 gph) on a squid and my SPS need more flow!). << Extra closed loop systems are great.  Really no reason not to have one.  But I think your drain will keep up. >> Much thanks in advance for all your help!  ~CK~  
<<  Blundell  >> <... what if there is some slowing down, occlusion here? I do wish there were more than one drain line... RMF>

- Bulkheads and Pumps -
Good morning WWM Crew.
I am in the process of planning the filtration/circulation for a 120 gallon salt water tank and would like you opinions on bulkhead/pipe sizes.
The tank, as of now, is going to be FOWLR. What I was thinking was a 1" line going to a 29 gallon refugium, a 1" line going to a 16 gallon sump, and a 2" line feeding a closed loop manifold.
Could you please advise on this or what you think would be more appropriate along with pump sizes to push all this. <As far as bulkhead sizes go, it all sounds do-able although two inches may be a bit excessive for a closed loop... at the very least make sure you have screens on the input and output sides so no one swims into it when the power is off. As for pumps... you're on your own there. There are many good brands and several sizes of each. Flow rates should be as high as is reasonable... if you could accomplish 10 to 20 times turnover for the system, you'd be doing well. Much more than that and you may be sloshing water out of the tank. However, I suggest you rethink the plumbing of the two one inch lines going to separate boxes... your overflow rate will be constant to both - if you put different sized pumps on each box, the one with the lower flow rate will eventually overflow. Much better, if you want a refugium to fill it directly from your main sump and let it gravity feed back into the main tank or sump.>
Thank you very much for your time and knowledge.
Troy
<Cheers, J -- >

Bulkhead sizes
Good morning WWM Crew.
<Good morrow to you Troy>
I am in the process of planning the filtration/circulation for a 120 gallon salt water tank and would like you opinions on bulkhead/pipe sizes.
<Okay>
The tank, as of now, is going to be FOWLR. What I was thinking was a 1" line going to a 29 gallon refugium, a 1" line going to a 16 gallon sump, and a 2" line feeding a closed loop manifold.
Could you please advise on this or what you think would be more appropriate along with pump sizes to push all this.
<Mmm, a few things... the drain lines need to be larger... at least 1 1/2" inside diameter... I'd make them 2"... and the discharge/manifold plumbing should be the diameter of the outgoing side of your pump volute, not larger>
Thank you very much for your time and knowledge.
Troy
<You'd likely benefit from reading the marine plumbing article and FAQs posted on WWM. Start here: http://www.wetwebmedia.com/plumbingmarart.htm
and on to the linked files (in blue, at top). Bob Fenner>

Drilled hole size and what to do with them.
Mr. Fenner,
                  First let me say how much I have enjoyed this site. I have learned a great deal but do get confused at times.
<I as well>
I am in the process of starting up a 150 Gal fish only tank, it has been 8 years since it was last running.
                 I read the entire plumbing section and got my tank drilled. I think it may be a bit too much though. I had 4 holes drilled that are 2 3/4 inch for the drains and one 1 3/4 hole for a loop return like you have described. The drains will empty into the basement 10 feet below. The sump is 55 gallon wet dry acrylic.
<Some through-puts now!>
                My questions are this........ Should I "cap" 2 of the bulkheads and just use two to return to the sump?
<I would, yes... unless you intend to have humongous flow through all four>
Should I use all 4 and connect two and two into a "Y" connection, or should I run all 4 to the sump?
<Could connect two of two together... but the cost of bulk-heads... I would likely run just two of the four together, and cap the other two>
BTW my wet dry has only two one inch holes drilled in the top. I will need to enlarge the holes to fit either 2 or 4 drain lines.
<Yes... or retro a drip tray, baffle of some sort to accommodate the flow from above>
                I am shooting for between 750-2000 GPH for flow rate. Did I overkill with the drains {4---- 2" pvc}?
<Mmm, yes, but better than under-killing it>
Hope this isn't too confusing. I am planning on plumbing to system next week and hope I didn't mess it up.
               Sincerely,
                                Jeff Resch
<No real problem to cut acrylic or glass and silicone over the other fittings. Bob Fenner>

Hole, bulkhead size
Hi I just got a 2inch hole drilled in my 135 gallon tank. what size of bulkhead would fit in here. I have a 1 1/2 inch but it doesn't fit. The base on that bulkhead in 2 1/2inches. Can you get a 1 1/2 inch bulkheads with a 2 inch base? hope this makes sense
Tristan
<Yes to the last statement. Look around... there are "thinner" outside diameter bulkheads (the ones for spas/Jacuzzis for instance) that have 1 1/2" inside diameter and less than 2" outside diameter. Spears makes these... and a few places (try MarineDepot.com) offer them for sale online. Bob Fenner>

Overflows
If it were your tank: How many & what size holes would you have drilled on the back wall of the tank (assuming a pump that can handle 3600gph at 6-8ft of head)?
<For a 180 gallon, likely six foot tank? Three, one toward each corner and one in the middle... of 1 1/2" inside diameter>
I have heard that the reason people do the in-tank overflow is that the water builds up after going over the overflow creating more of a vertical push into the outflow tubes vs. a couple top of the back tank holes which outflow horizontally.  Does that make a substantial difference for flow?
<Mmm, am concerned I may not be understanding you here, but the only real difference in such arrangements is the addition of horizontal piping, fittings, rather than more initial vertical drop>
If I understand you correctly, it sounds like your advice would be to drill 2-3 holes on the upper back tank walls, use bulkheads & screw in strainers, and then on the outside of the back tank wall, simply connect hard or soft plumbing leading to the sump?
<Yes>
What distance is advisable for the holes to be drilled from the top of the tank?
<Two or four inches in this case/size bulkheads... to either attach screening horizontally or (with the four inch gap) attach threaded elbows... Bob Fenner>

Placement of drilled holes in tank 6/18/05
Hi crew,
<Howdy!>
Haven't been in touch for a while (6 months or so)
<Nor I... with reality. Hoping to return one day... enjoying the view in the meantime :)>
but I wish to ask what may seem a fairly straight forward question but one which I seem to be getting several answers. I will try to explain keeping it as short as I can.
<Rock on my salty brother>
  a.. Briefly:- Ordered new tank 48"X18"X24" high. Asked for two holes (2"each) to be drilled in back panel  near the top. (To go to sump)
<Excellent>
  b.. One week later received phone call to say they could not do this and had broken two panes of glass trying.
<Strange... I have the same sized aquarium with two 2" holes as well as two 1" holes. They must have had poor skills/equipment. No flaw of the tank/size here>
  c.. Company asked me if it were ok if they drilled the holes at the bottom of the back panel instead?
<Yikes! What's the difference in glass/panes?>
I said that would be fine but suggested they drilled the at the bottom and then turned the glass up the other way so the holes were at the top ;-)
<Ha! Spot-on my friend!!!>
  d.. (I think they were trying to drill it after construction)
  e.. Anyway. Received tank with two holes drilled in rear panel RHS one above the other with a weir !
<OK. Are the holes split? That is to say, one above and one below the weir? If so, make the bottom a closed loop manifold intake>
  f.. Messed around and got tank working but found the weir was too high and for the water overflow the weir I had to fill the tank until the water touched the cover glasses.....Not good.
<Ughhh.>
  g.. Phoned company and complained. They agreed to replace the tank with a new one to my specifications. And that is where I am right now. The tank will be a reef tank and I would like to move my remote 6" deep sand bed to the display tank itself. This will leave one sump for Algae growing to transport nitrate from the tank. The tank size will be 48" X 18" X 30" high. (the extra 6" on the new one to accommodate the DSB). Filtration will be this DSB, plus large protein skimmer, live rock, carbon & ozone.
<All good>
My question/s is/are this.
Where and how would you build the holes for the outlet to the sump? Bearing in mind I am following you guys example and hope to turn the water over between 15-20 times per hour. Would you incorporate a weir?
<Yes... I do strongly prefer an internal weir (internal overflow) to improve the quality of (concentrated) protein-rich skimmed water>
I hope you can help me out as I do not want to fall into the same traps I have before.
<Do check the archives (keyword search from our home page) for "internal overflow" and "marine plumbing". Lots of pages here to consider. Also... I have several link heavy threads with pictures/examples of the closed loop manifold and internal overflows in my "All Things Salty" forum at reefcentral.com. As far as how many/which size holes to use. My advice is actually to have a modest amount of water (say 5-10X turnover) make the loop between the sump and display. This will keep things quiet in the sump and spare turbulence/micro-bubble problems with aspiration through the return pump. Then... use the/another (drilled a few inches lower in the tank) 2" hole for a closed loop pump (this does not enter the sump loop circuit). to provide the rest of the tanks water flow needs in the display proper. Much quieter overall. :)>
Keep up the great work and don't please ever give up this site!
Best wishes to Bob, Scott, Marina and all of you.
Cheers, Simon.
<best regards, Anthony :)>

Placement of drilled holes in tank II 6/20/05
Hi Anthony, Really appreciate the reply, very helpful thanks.
<You're always welcome bro>
The question about the holes? No, they are not split they are one above the other and the weir encompasses them both.
<Wow... a very deep overflow indeed if horizontal>
But, that doesn't matter now that they are going to replace the tank. I would like to pop another question or two your way, before I give them instructions on building the new tank. It's very helpful to know that the complete 15-20 times per hour turnover does not have to pass through the sump. This does solve a few worries, thanks again for that one.
<Very good... and it opens the door for more flow if you go with Acroporids, for example>
What I really want to know now is, if I build the tank with two 2" holes for the outlet to the sump in the back panel at the top and two 1" holes for the return,  where and how would be the best way to surface skim the water?
<This depends on the style/model of skimmer you choose. Do see the excellent skimmer threads we have in my forums (stickied at the top) at reefcentral.com (skimmer performance) and reeffrontiers.com ("skimmer 101" thread)>
where would the weir go exactly?
<If horizontal... as low and long as possible. About 6"/15cm deep and about as wide or a little bit thinner. And running the length of the tank as much as possible. This will thin the surface extracted water and greatly improve skimmer production. Do a search for "internal horizontal overflow" on this site and the others listed above for more info on this. Or peek in my first chapter of the Book of Coral Propagation for an illustration and detailed description>
Would it be best to have an end to end weir at the top of the tank?
<Yes>
Also how far down from the top of the tank will be best to have the TOP of the 2" holes and the 1" ones come to think of it?
<As close to the top of the tank as is sound/possible. The depth of the overflow that holds these two holes will likely be no more than 6"/15 cm at the top of the tank>
Sorry to fire so many questions at you but you guys have certainly saves me from a  disaster or two in the past. (That reminds me, I owe a cold beer to all of you!)
<Looking forward to it :)>
Oh, one last thing. If I use powerheads (Tunze streams, thanks to Anthony and/or Scott, I would use nothing else now, they are brilliant!!) do I count these in the equation regarding total water turnover?
<Yes... certainly>
Cheers again. Simon.
<Best regards, Anthony>