TANK FLOW CONFIGURATIONS

[PJsea]

I am new to this hobby so these questions may seem obvious. Right now I have a small reef tank but will be looking to get something larger within a year and have questions about setups.
I will probably be getting a glass tank with capacity of 120-180 gal. with overflow boxes and holes drilled. I've seen tanks with numerous holes drilled in the bottom and was wondering what different ways to pipe them up.
I may have misunderstood but someone told me the water would be returned to the overflow box. This seems a little inefficient to me since you would be mixing outgoing water with return water and not getting movemnt in the tank. I'm assuming this would be done to get protection from draining tank completely in event of leak. Why not pump it back to tank to manifold of some kind?

Also seen tanks with holes drilled in bottom of main section. I'm guessing closed loop systems for cooling and/or water movement or were these intended for return flow from sump? I'm also assuming these would have some kind of standpipe to prevent complete loss of tank water.
What other uses would these provide? Would this involve the several loops because one pump would be too weak or flow in parts of the system would be too high?

 

[Mihai]

You're on the right track. We all had these kind of questions when we started. Things will look obvious after a while, but at the beginning they don't.

Regarding the first question: nobody returns the water to the overflow (for the reasons you stated), but many choose to return it through the overflow (so you don't have pipes at the back of the tank).

Regarding the second one: yup, right again, the bottom ones are mainly used for closed loops. But people usually don't use standpipes for the bottom holes (would be very ugly in the tank), but rather take the risk of a completely empty tank if such a closed loop leaks. Personally I'd never do that, but that's me.

M.

 

[Anonymous]

What Mihai said. One way to prevent a closed loop leaking and draining your tank is to simply install it so any drips will fall into your sump. Problemo solved.

 

[Mihai]

What Mihai said. One way to prevent a closed loop leaking and draining your tank is to simply install it so any drips will fall into your sump. Problemo solved.

Sure, if you have this luxury do it this way. I have a basement sump and my living room will flood first (although I can make sure it overflows in the sump eventually ).

M.

 

[PJsea]

Thanks; logically it seemed that it wasn't the way it should be, but at the time there were no holes cut in the skimmer for a return pipe.
Are there any "rules" regarding number of overflow boxes for a particular size tank(i.e. so many inches of skimmer per 100 gallons of flow) or do you just make sure you have enough holes(sized properly) to give you the flow you want?
I see my setup having the internal overflow at one end because it will be used to divide a couple of rooms with the end against a wall. Three sides will be open for viewing. How much flow is recommended thru the sump and what kind of flow would be recommended for water movement in the tank?

 

[Mihai]

Yup, there is such a rule, I just don't know what it is. I found it somewhere, something as x00 gallons per hour for 10 inches of overflow.
Large tanks tend to have two overflows both because of the flow/inch rule, as well as redundancy. Furthermore, there is a limit the overflow pipe can handle. E.g., an 1" pipe usually can do 600gph conservatively, probably a bit more in reality.

For the tank you want to turn the entire volume between 10x and 20x per hour. For example, for an 120gal you want 1200-2400 gph. The SPS tend to want toward the higher end of the interval.

For the sump, the opinions are split, but IMO you don't need too much - once - twice per hour (with no upper limit, really). I'll probably get flamed for this opinion, but so far nobody gave me a reason better than "That's how I do it".

M.

 

[Playdope]

Not intending to hijack, but... when you say:

For the tank you want to turn the entire volume between 10x and 20x per hour. For example, for an 120gal you want 1200-2400 gph. The SPS tend to want toward the higher end of the interval.

Are you referring to the sum of all flow in the tank - exernal pumps (closed loops, return pumps, spraybars, etc.. powerheads..etc.. ?

I am currently running the following on my 5ft. long 100, and it seems pretty turbulent in there:

Iwaki 30 RLT (return pump)
Iwaki 30 RLXT (closed loop - split to 2 return inlets)
Tunze powerhead with controller (the weakest one... but man this thing can be a firehose)
Maxijet 1200 powerhead (breaking surface)

... it's like... when I look at the substrate, I want to turn the flow up on the Tunze more because I see some detritus... but if I did the corals would blow around way too much it seems. Could it be that I need more critters to stir up the sand? I only have one small fighting conch right now who spends the whole day poking around in the sand, but it seems like I need another one or some something else to consume detritus.

I realize detritus will be produced by the "detritus-eaters", however, it would be nice if they could somehow make the waste more skimmable... not sure if thats a foolish thought.

 

[Mihai]

Not intending to hijack, but... when you say:

For the tank you want to turn the entire volume between 10x and 20x per hour. For example, for an 120gal you want 1200-2400 gph. The SPS tend to want toward the higher end of the interval.

Are you referring to the sum of all flow in the tank - exernal pumps (closed loops, return pumps, spraybars, etc.. powerheads..etc.. ?

Exactly. The sum of all flows (no the flow rate on the pump, what actually gets in the tank after substracting all the height and turns).

Regarding detritus - it's best if you can blow it off with your flow. What you'd like is to get more volume moved, but not too much speed (something like a spray-bar - lots of volume but small speed). You detritivores will just eat it or work it into the sandbed, I don't think they'll blow it in the water column where the flow can take it away and skim it. Unless I'm missing some detritivores - maybe fish could do that...

M.

 

[Playdope]

Whats the best way to make an "invisible" spray bar? The last thing I want to see is a hunk of pvc coming down the back of the tank.

 

[Mihai]

What I use is what's called a "manifold", i.e., a pipe with a bunch of nipples running at the top of the tank with only the nipples submerged.
Other than that you can hide the spraybar behind the rocks (put it horizontally).

M.

 

[Mcg180]

If noise is a consideration, which I assume it is since the tank will be used as a divider fro two rooms, give careful consideration to the flow through the overflow drains. Overflows can be noisy if you attempt to run too much water through them. Mihai has it correct, a 1 inch drain will handle approx 600 gph perhaps more. You will need to use durso style standpipes to eliminate the cascading sound effect, however even at that rate the water tends to have a drain sound (ie, similar to that of hearing a tub draining through the wall). Best bet would be to oversize the drains and then use closed loop systems to keep a higher overall turnover. Sounds like you will need to have a custom tank built for the one overflow box placement. In that case you will want to make the box wider than a typical overflow box especially considering that a typical 180 (assuming six foot length) has two overflow boxes. The obvious purpose of the overflow is to collect surface water for delivery to the sump and more importantly the skimmer. The wider overflow will help maximize surface contact and water collection given the unique placement in your set up. Just my 2 cents.

 

[Mcg180]

If noise is a consideration, which I assume it is since the tank will be used as a divider fro two rooms, give careful consideration to the flow through the overflow drains. Overflows can be noisy if you attempt to run too much water through them. Mihai has it correct, a 1 inch drain will handle approx 600 gph perhaps more. You will need to use durso style standpipes to eliminate the cascading sound effect, however even at that rate the water tends to have a drain sound (ie, similar to that of hearing a tub draining through the wall). Best bet would be to oversize the drains and then use closed loop systems to keep a higher overall turnover. Sounds like you will need to have a custom tank built for the one overflow box placement. In that case you will want to make the box wider than a typical overflow box especially considering that a typical 180 (assuming six foot length) has two overflow boxes. The obvious purpose of the overflow is to collect surface water for delivery to the sump and more importantly the skimmer. The wider overflow will help maximize surface contact and water collection given the unique placement in your set up. Just my 2 cents.