Flow Pattern Help


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Hello, I'm setting up a 63g acrylic REEF tank and I was looking for diagrams/information on a flow pattern to use. People have been telling me to get the general idea for flow, but I have no idea what they're talking about or where to start... a circle tornado effect?... all in?... all out?... a figure 8? The goal is to HIDE all of the plumbing and drill from the BOTTOM. I'm trying to do this without bulky powerheads. Since I have NOT drilled yet, I was wondering if anyone can lend some advice?

- maximize water flow, but do not blow out planned corals
- reduce algae harvesting areas

There will be 2 pump systems, a closed loop generating about 1000gph flow and a sump returning about 400gph flow.

The closed loop intake drain bulkhead will be in the bottom (exact center) middle of the tank camoflauged by a LR bridge. The returns are planned to be directly at the 3 & 9 o'clock positions about 1.5' away (meaning that they are in the middle widthwise of the tank as well). I was thinking that these would split into 2 outputs each.
- Only 2 outputs each or should I split these 2 returns to 3?
- What's the name of the bendable ball-n-cone like tubing that directs water from these things (so I don't sound utterly stupid any more)?
- This was planned to have a SCWD on it, but some have advised against using one?
- I can drill the returns other places in the tank, but I was going to hide it under LR with only the heads of the whatchmacallits returning the water. Advisement?

The sump drain and return will be housed behind an INSIDE overflow box in the back with the 400gph return. I really only want 2 holes in the bottom of the tank here.
- Should I split the return flow back into 2?
- Since I only want to drill 2 holes (drain / return) if I were to put the SCWD here it would have to fit after the return makes it back into the tank splitting into 2. Has this been done before? Is this okay?


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Thank you waterkeeper. Does anyone have any diagrams? I'm not sure what is advised, when they say figure out your general flow pattern and then you can fine tune later. I'm not even sure what a general flow pattern is?


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Amen brother, I'll be watching this thread close since I'm in the same situation the only exception is my tank is 150g.
What kinds of livestock are you hoping on supporting?

For smaller tanks, I like to keep any given flow source to 10x tank volume. Much more than that in a small tank usually means you'll end up with huge variations in flow, and sections of the tank where the current is way too powerful. So, with a 63 gallon tank, I would break any flow stream up until it was in sections of, say, 500 - 600 gph each.

Positioning those is based on three restrictions:

1) Aesthetics. You've mentioned that you want to hide stuff. Of course, this will impact your placement.

2) Substrate choice. If you're using a fine sand, you WILL be pulling your hair out by the end of this project, after struggling to create a flow pattern that doesn't constantly blow the sand around into bare spots and drifts. Don't worry though, as the sand becomes coated in biofilm, it'll stick together a little better and tend to stay in place.

3) The rockwork. You don't really want any output blasting directly AT the rockwork, at least from close range. What you want is to create lots of flow very close to the rockwork. So try to aim the outputs so they are either parallel to the face of the rock, or glancing off it. Don't aim an output off into open space unless there's a really good reason to, i.e. to create turbulence by intersecting other flow sources or because that output is way too powerful to do anything else with.

Within the framework of those two restrictions, you need to plan so that every section of the tank is getting "good" flow. If a section of rock will have lots of SPS or other high flow corals on it, you obviously need more flow there than in some empty corner of the tank behind the rockwork. However, that empty corner needs at least enough flow to prevent the accumulation of waste and growth of nuisance algae. In a super high flow tank, i.e. one set up for SPS, you'll probably have enough flow such that there won't be any of those dead spots. In lower flow tanks, you do definitely need to plan for that, though.

Now, how do we define the "good" flow that we want near out corals? We can never imitate the sheer inertia of water movement on a real reef, but hopefully we can come close. Rather than aiming for velocity of flow, aim for inertia - i.e. it might be better to be moving a WHOLE lot of water at a slightly lower speed, rather than a very narrow stream of very high flow shooting across the tank. That's another reason to break up your flow into several outputs, but also to keep the plumbing sizes up on those outputs.

In addition to thinking about moving ALL the water, it is traditionally believed that having some randonmess and turbulence is a good thing, as well. To get turbulence, point outoputs at eachother, or so that they're glancing off rockwork or the walls of the tank. To get random flow, use something like a SCWD as you mentioned. The problem with SCWD's is that they tend to add a lot of head to the plumbing, which in layman's terms means they restrict the flow quite a bit. So if you have a pump that you think will output 1000 gph on your system, the SCWD might add enough loss to bring it down to 700 or 800 or something like that. You can get around that by upsizing your pump, but you have to be aware that the SCWD's have limits. Also, the more flow you push through them, the faster they switch - that might sound like a good thing, but by the time you get down to a 2 or 3 second interval, you really aren't giving the water any chance to build up momentum or inertia. Imagine stirring a pot of water in the same direction for 20 seconds, then quickly switching to the other direction for 20 seconds. You're building up a LOT more momentum in the water than if you'd switch every 2 seconds. You definitely want some of the churning action of the shorter interval, but momentum is very important, as well.

(BTW, There are other devices for switching water current that are more robust than SCWD's, but they are also much more expensive.)

All that said, as indicated in the article above, you really can't plan it perfectly the first time. Your best bet is to plan for having your points of flow spread out across the tank as well as possible, then re-aiming them as required once you've got things running. The stuff you're referring to is loc-line, and though it is certainly flexible, it's also somewhat lossy compared to straight PVC fittings. I've found that if you start with a bunch of small pieces of pipe and a bunch of different elbows, you can get regular PVC to point anywhere you want. If you don't want to glue it, just wrap a couple layers of Teflon tape around each joint and push it on tight. That'll hold it together well enough for aiming water flow within the tank, but it obviously isn't permanent or water-tight for plumbing outside the tank.


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I'm sorry what does "SCWD" stand for? I assume it refurs to devices like Ocean Motions Super Squirt 4-way device?


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The November 2005 editon of Reef Keeper Mag has a tank with a nice flow diagram and explination of how and why he did it.


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Thank you Der! Possibly the most in-depth explanation that I've received here on RC.

I'm aiming for softies to start, and and in the future maybe some LPS. Once I get a GREAT handle on things, I'll maybe venture into SPS, but I think I'd have to do some upgrading in lighting prior to that.

The 10x any given source is a good piece of information to know. The plan was 1000gph for the closed loop 2 returns, and 500gph (not factoring the head loss) from the sump. I'm figuring 20x right now. I'm kinda reserving the back corners for the powerheads when I jump to SPS needing 30x.

The CL returns are going to come FROM the LR structures (bottom of tank returns). The sump return is going to come from behind the overflow. I like your advice to aim them parallel to the rock wall, becuase I was planning on just aiming them all diagonally outwards if no one advised me.

The aquascape is going to be 2 islands hybrid with a pass through cave in one of them. So maybe a direction through the pass through towards that back of the tank. One going forward towards the front, another pushing across the front. And lastly from the back pushing towards the front. I'll quickly make a diagram and attach later.

Could you look it over and give me some feedback?
Aiming them diagonally outwards would probably be fine in a softy tank, but taking that approach generally just stirs the water out in open space and not near the rock where your corals are - unless you have very powerful pumps.

Plan now for that upgrade. If you're putting in a closed loop system, don't rely on powerheads down the road for expansion - that's kind of backwards, IMHO. Plan the closed loop plumbing so it can handle a bigger pump/more outputs, then invest in the bigger pump later if you want to go SPS. Or, plan for a second closed loop down the road.

Looking at the specs in your sig, you're right - you'd need more lighting to support SPS or other demanding corals. Nothing wrong with what you have for low light stuff though, of course. 20x tank turnover should be plenty in a softy tank, though you're right - you will probably want at least 30 - 40x in an SPS dominated tank. Some people with barebottom SPS tanks are probably running more like 80x.


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General Flow Pattern

General Flow Pattern

Okay... don't laugh... my excell spreadsheet drawing. I don't have paint. javascript:smilie(':D')


  • general flow pattern.xls
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Wow, talk about creativity!

Seriously, that looks like a good plan. I really like the aquascape concept. The island off to the front-left should provide some interest. I like to have rockwork that obscures parts of the tank, I find it instantly makes viewers move around and try to see what's back there.

The flow pattern looks like a good starting point, too. Looks like you have every section of the tank pretty well covered. Will all of the returns be low down in the tank, or will the return from the sump be up near the water level? IMHO you might want the sump return up high, and I'd even split it. With all of the closed loop outputs low down, you'll want something to keep the whole top layer stirred. Of course, you could aim the closed loop outputs upwards into the tank, too.


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Thanks Der! It means a lot to me that you like it. I've always liked the 2 islands look, and bridges, but with a bulkhead drain in the middle, I had to hide it. The right side, needed to hide the overflow box so it all just kinda came together naturally (accidentally in my case). I REALLY appreciate your input though, because I was VERY lost in how the flow of water was going to be.

Great idea to put the sump returns up high. Two questions... if I put a SCWD on, does it change your opinion (cyle on CL between R & L)? Second question... should I consider splitting the CL returns into 3 (instead of both splitting into 2)?


Bogus Information Expert
Premium Member
You know, no matter what people say ;), that Willie is a pretty knowledgeable guy. :thumbsup:
Sundevil, were you going to put the SCWD on the closed loop or the sump returns? Personally, I feel that you're at too high a flow on your CL - you'll get a lot of head loss and a really fast switch. Since the majority of your flow is coming from the loop, I don't think you'd want to impose those conditions on it. It might work better on your sump returns.

Splitting the CL returns into 3 would give more options, but would be pretty low flow through each. I do like the fact that it would give more flexibility though, so if you go that route, you could bump up to a bigger pump to compensate. If you found that it was too much flow for your planned corals, you could just throttle it back with a valve - you'd be all set for future expansion that way.

Tom - I've got a loooong way to go before I attain your level of bogus information expertise! ;)


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For my closed loop design I am thinking about having 2x 1" intakes, and then return with 4x 1/2" two would be in the front of the LR formations pointing up and across and the other two coming from behind the rocks pointing down and glancing off the side glass and thinking about putting in one of the Ocean Motion units. For my sump return I was thinking two returns at the top of the tank pointing... somewhere.... Am I close or way off base?.... Sorry to but in on your thread SunDevil =)


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Lock line is the return device you want.
I have found that a circular flow pattern works good.
If you plant your returns low and aim them up you can generate a good flow from the bottom and still not disturb the sand..
If you maintain space all around the rock pile it will keep to nature
in that sense. If you study natural flow in the oceans you will allways have a constant flow in a northerly or southernly direction
depending on what side of the continent you are on.
The Oceans flow in a clockwise fashion. So I say place your rock in the middle and make the water flow around it. Use a little less rock and give more room to the fish and corals!!!
<a href=showthread.php?s=&postid=10467585#post10467585 target=_blank>Originally posted</a> by Thinslis
For my closed loop design I am thinking about having 2x 1" intakes, and then return with 4x 1/2" two would be in the front of the LR formations pointing up and across and the other two coming from behind the rocks pointing down and glancing off the side glass and thinking about putting in one of the Ocean Motion units. For my sump return I was thinking two returns at the top of the tank pointing... somewhere.... Am I close or way off base?.... Sorry to but in on your thread SunDevil =)

Sounds good, but make sure you aren't downsizing your return plumbing too much. I lost track, but for the closed loop, were you talking 4 1/2" returns? That's nowhere near the equivalent area of a single 2" intake, so make sure it won't be restricting your pump too much.

Also, keep in mind that if you use an OM or other switching device, the usually switch such that ALL the flow is going through only a few of the outputs, so typically it's a good idea to have the outputs all fullsized plumbing.

Otherwise, sounds pretty good.


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So if I have 2 one inch intakes I should have 4 one inch outlets? My first post was 2 one inch intakes and 4 half inch outlets.

But if I read you correct Wille, I would want one inch outlets to match my intakes?