Refugium or Skimmer section?

[meemsco]

Hi all!

I am new to saltwater hobby and I am building my first sump. Reading a lot of information and know I need to just dive in and learn in the process. I have a 75g DT and I can barely fit a 29gal sump underneath. Originally, I wanted a skimmer section and a refugium section, but I read on gmacreef that 29gal sump is a bit small for both in case of power failure - ie: with that many chambers, it would be a bit tight on left over volume for back flow. He recommends only have 2 chambers , so either for skimmer/refugium and then return chamber....not all 3 chambers.

So my question is: 1) would 29gal sump be big enough for the power failure overflow if I have 3 chambers? Or would you recommend only 2 chambers? 2) If I only have 2 chambers, which would be more important to have - a skimmer or a refugium? (I also have a small section for filter sock).

Thank you!

 

[Quietman]

I don't think the blanket statement of X gallons for sump is good or bad for back-flow protection can be made.

It's going to be the difference between running volume and max volume your sump can hold.

Take your sump design, measure each compartment include height of water each is expected to run at (height of baffle before next section usually). Add that up. Subtract it from the total the sump will hold (inside measurements of total length/height/width) - that's the amount of water your sump can hold before overflowing.

You can calculate how much the drain will flow into the sump by adding up the drain and return piping and the water height normally above the drain. But test it operational before trusting math completely.

FYI - length (in) x width (in) x height (in) / 231 = gallons.

 

[Rolrod39]

I would recommend a refugium and a skimmer. You could even use a hang on skimmer if there is not enough room in the sump. It also helps with the pH stability when you have the light on the refugium when the display tank light is off.

 

[Twinanoreef]

Are you sure you can't squeeze a plastic cage or a plastic breeder box to serve as a refugium in 29 gallons?

 

[meemsco]

I don't think the blanket statement of X gallons for sump is good or bad for back-flow protection can be made.

It's going to be the difference between running volume and max volume your sump can hold.

Take your sump design, measure each compartment include height of water each is expected to run at (height of baffle before next section usually). Add that up. Subtract it from the total the sump will hold (inside measurements of total length/height/width) - that's the amount of water your sump can hold before overflowing.

You can calculate how much the drain will flow into the sump by adding up the drain and return piping and the water height normally above the drain. But test it operational before trusting math completely.

FYI - length (in) x width (in) x height (in) / 231 = gallons.

Thanks, I did exactly that - used that formula and calculated all the chambers using the height of the baffles, and it is cutting it close if I have both a chamber for skimmer and one for refugium.

I do have another question -- I ordered a sump DIY kit and looking at it, there are what looks like weirs (don't know what else to call them) in the MIDDLE of each baffle. Why are those there and would that affect the water level of each chamber?

I also have been calculating the water volume of each chamber using the HEIGHT of each baffle for each chamber, but if there are these weirs in the middle of the baffle, wouldn't the water just fill to that level and run into the next chamber and never fill up to the height of that baffle? That would also be a problem because these weirs are only 3-4" from the bottom. Would the water only fill to that level and then run into the next chamber? That doesn't make sense to me especially if I need the water level to be like 9" for a skimmer?

I hope I am making sense. Very new to this and just trying to understand as I am going along and running into things.

I am attaching a couple of photos of the kit so you can see what I am talking about. THANK YOU for your help.

 

[christian321uy]

skimmer and refugium with chaeto works best imo.

 

[Quietman]

Thanks, I did exactly that - used that formula and calculated all the chambers using the height of the baffles, and it is cutting it close if I have both a chamber for skimmer and one for refugium.

I do have another question -- I ordered a sump DIY kit and looking at it, there are what looks like weirs (don't know what else to call them) in the MIDDLE of each baffle. Why are those there and would that affect the water level of each chamber?

I also have been calculating the water volume of each chamber using the HEIGHT of each baffle for each chamber, but if there are these weirs in the middle of the baffle, wouldn't the water just fill to that level and run into the next chamber and never fill up to the height of that baffle? That would also be a problem because these weirs are only 3-4" from the bottom. Would the water only fill to that level and then run into the next chamber? That doesn't make sense to me especially if I need the water level to be like 9" for a skimmer?

I hope I am making sense. Very new to this and just trying to understand as I am going along and running into things.

I am attaching a couple of photos of the kit so you can see what I am talking about. THANK YOU for your help.

The water height will go to the highest baffle downstream. If there's lower in the middle water will raise on both sides to equal the downstream baffle height. Those slots in the middle are to keep the algae from leaving the fuge and still have water flow through middle.

 

[meemsco]

The water height will go to the highest baffle downstream. If there's lower in the middle water will raise on both sides to equal the downstream baffle height. Those slots in the middle are to keep the algae from leaving the fuge and still have water flow through middle.

Very much appreciate your help! I feel like I can finally build my sump!

 

[Quietman]

Anytime. Please share some pics when your done. Better yet, start a build thread!

 

[meemsco]

The water height will go to the highest baffle downstream. If there's lower in the middle water will raise on both sides to equal the downstream baffle height. Those slots in the middle are to keep the algae from leaving the fuge and still have water flow through middle.

Hi Quietman,

I have one more question! Will the water height for the tank be set by the last clear baffle at the end or the adjustable black/white one? I was hoping that that huge slot in the bottom of the clear baffle might change how the water flows, but my guess is that the water height will be set by the clear one? Also, with power failure back flow, would the return chamber fill up to the level of the clear baffle, then flow over that clear baffle into the other chambers? Does the big slot at the bottom of that clear baffle change anything I am thinking with the water height/flow?

I am asking all this because my backflow volume is cutting way close. If that clear baffle is what is setting the water height in the entire tank, then I have to get someone to cut it down or my sump will overflow. It is currently 15" tall! My skimmer only needs 9".

thanks for your help!

 

[Quietman]

It'll be the adjustable one - that's why it's adjustable!

The last clear one has the opening on the bottom to direct water through the media/sponge racks into the pump chamber.

So, let's see I was trying to find some animation to show how sumps work as it can be a little confusing until you "get it". I've seen one before, but didn't save location - I'll keep looking, but in the meantime..

Sumps have two states: 1) Return pump on and 2) Return pump off.

In state 1) with the return pump ON, it is supplying the energy to drive the system. So everything else in the sump has to be viewed relative to the pump chamber end. This will be lowest level in the sump. The water coming into the system in the drain section would be the highest level. Water flow in the sump has flow "down" to the pump chamber.

The great thing about this is you can take advantage of that to set level to run skimmers or reactors for example. However, you can also use baffles with holes in middle or bottom to route flow through media/sponges, create flow for refugiums and remove bubbles through traps (2 or 3 baffles configured to allow bubbles to dissipate through change in flow and direction).

Key points you're concerned with are that if water has to flow OVER a baffle and not through it or under then that baffle is setting upstream height. If water is flowing through the baffle or under it, then it's used for directing flow only.

In state 2) with the return pump OFF, gravity and amount of water available to drain into the system are the driving energy. Baffles in this case really do not matter since no water is being removed from the sump. Water will fill from two sources, the drain (normal and this will stop when the display level drops to weir level or drain pipe level in the display tank) and the return pump back flow. If your return nozzle in the tank is too low, this source of water can be excessive due to siphoning that can occur. So best practice is to have return nozzle high in tank (mine is no lower than the weir for the drain) and/or siphon breaks (small hole that's drilled high in return line in display that becomes uncovered with level drop stopping the siphon effect limiting how much water can drain.

The maximum water level in sump in state 2) return pump OFF is the combination of the drain and return lines emptying into the sump. This can exceed all baffles in the sump.

Two main issues in high sump level - one you need to make sure when you turn the return pump off (or power loss to everything) that the combined water from the drain/return doesn't overflow the sump. That's the tank walls and not the baffles. Otherwise, water on floor, carpet, cabinet, etc.. That's the really bad.

The other is if you're turning off return pump for maintenance and/or feeding (some do), you want to make sure your skimmer isn't running or starting from too deep a water level. This isn't that bad but can impact skimmer performance and dump skimmate back into tank. This is managed by turning off skimmer before return pump is turned off and by starting your return pump first and then powering back on your skimmer after running sump level is achieved (state 1). There's also time delays available, controller settings, skimmer selection that can moderate this impact too.

Whew - Sump 101 I guess. Hope that helps.

 

[Admann]

I don't think the blanket statement of X gallons for sump is good or bad for back-flow protection can be made.

It's going to be the difference between running volume and max volume your sump can hold.

Take your sump design, measure each compartment include height of water each is expected to run at (height of baffle before next section usually). Add that up. Subtract it from the total the sump will hold (inside measurements of total length/height/width) - that's the amount of water your sump can hold before overflowing.

You can calculate how much the drain will flow into the sump by adding up the drain and return piping and the water height normally above the drain. But test it operational before trusting math completely.

FYI - length (in) x width (in) x height (in) / 231 = gallons.

Don't forget the displacement of water volume by sand, rock, skimmer, pumps, etc. They all take up that precious volume

 

[Quietman]

Don't forget the displacement of water volume by sand, rock, skimmer, pumps, etc. They all take up that precious volume

True on total volume, but that shouldn't figure heavily into sump volume calculations on overflow. Water level in display is going to be above all equipment and normal sump running volume has all the equipment below waterline.

 

[Admann]

True on total volume, but that shouldn't figure heavily into sump volume calculations on overflow. Water level in display is going to be above all equipment and normal sump running volume has all the equipment below waterline.

I was speaking to the displacement of volume in the sump only by those items I mentioned. The true volume of the sump is affected by those things, return pump flowrate can in some cases cause flooding due to stacking in the display. The pump shuts down and in an uncluttered sump it probably wouldn't be a problem with high flowrates. There are many things to consider and I agree with you that actual controlled testing with all equipment in use and in place will always be fool proof.

 

[meemsco]

It'll be the adjustable one - that's why it's adjustable!

The last clear one has the opening on the bottom to direct water through the media/sponge racks into the pump chamber.

So, let's see I was trying to find some animation to show how sumps work as it can be a little confusing until you "get it". I've seen one before, but didn't save location - I'll keep looking, but in the meantime..

Sumps have two states: 1) Return pump on and 2) Return pump off.

In state 1) with the return pump ON, it is supplying the energy to drive the system. So everything else in the sump has to be viewed relative to the pump chamber end. This will be lowest level in the sump. The water coming into the system in the drain section would be the highest level. Water flow in the sump has flow "down" to the pump chamber.

The great thing about this is you can take advantage of that to set level to run skimmers or reactors for example. However, you can also use baffles with holes in middle or bottom to route flow through media/sponges, create flow for refugiums and remove bubbles through traps (2 or 3 baffles configured to allow bubbles to dissipate through change in flow and direction).

Key points you're concerned with are that if water has to flow OVER a baffle and not through it or under then that baffle is setting upstream height. If water is flowing through the baffle or under it, then it's used for directing flow only.

In state 2) with the return pump OFF, gravity and amount of water available to drain into the system are the driving energy. Baffles in this case really do not matter since no water is being removed from the sump. Water will fill from two sources, the drain (normal and this will stop when the display level drops to weir level or drain pipe level in the display tank) and the return pump back flow. If your return nozzle in the tank is too low, this source of water can be excessive due to siphoning that can occur. So best practice is to have return nozzle high in tank (mine is no lower than the weir for the drain) and/or siphon breaks (small hole that's drilled high in return line in display that becomes uncovered with level drop stopping the siphon effect limiting how much water can drain.

The maximum water level in sump in state 2) return pump OFF is the combination of the drain and return lines emptying into the sump. This can exceed all baffles in the sump.

Two main issues in high sump level - one you need to make sure when you turn the return pump off (or power loss to everything) that the combined water from the drain/return doesn't overflow the sump. That's the tank walls and not the baffles. Otherwise, water on floor, carpet, cabinet, etc.. That's the really bad.

The other is if you're turning off return pump for maintenance and/or feeding (some do), you want to make sure your skimmer isn't running or starting from too deep a water level. This isn't that bad but can impact skimmer performance and dump skimmate back into tank. This is managed by turning off skimmer before return pump is turned off and by starting your return pump first and then powering back on your skimmer after running sump level is achieved (state 1). There's also time delays available, controller settings, skimmer selection that can moderate this impact too.

Whew - Sump 101 I guess. Hope that helps.

Thank you for all of that! I really appreciate your help. I have researched, and went to local LFS to see established sumps, absorbing all I can without fully seeing it in action from start to finish.

I am still really nervous about my volume measurements. I calculated 6.5 gals if everything failed (ie: the anti-siphons) and giving myself 1" or 1.5" (I forget which one) below water surface on the return for safe measure. And if that is what happens, by my calculations, the sump will not hold the overflow. But if the anti-siphons work and I keep my return at 1/2" below the surface, I think I will be okay. I plan on drilling anti-siphon holes, and a check valve for the return. But I am still nervous.

Based on what you shared, would the number of chambers would affect the amount of overflow that the sump can handle? (Because you said it the tank walls that dictates it, not the baffles). Gmacreef.com recommends only having 2 chambers so that the return chamber is large enough to handle the backflow. He said having 3 chambers might make the return chamber too small so it wouldn't be able to handle the overflow volume. (https://gmacreef.com/reef-tank-sump-diy-glass-baffles/ ....... it is in the comments section dated 9/16/16 in case you need the reference)

The other option is just to omit the refugium and just do skimmer and return chamber, then I know I will be safe. Thoughts?

thank you so much!

 

[Quietman]

Ah good..excellent research and questions.

I'm going to respond in two ways - failure of your backups and normal operations. Because when everything fails I want dry wood floors but for normal feeding/maintenance I don't mind relying on those backups working.

Failure of backups
If your sump cannot hold the volume of overflow when you turn off the return pump without relying on siphon holes and check valves, I would have some concerns.

Check valves can and almost surely will fail (snails if nothing else). Siphon holes can clog up as well.

If you can permanently fix your return nozzle high enough to prevent overflow, that would be acceptable to me as it doesn't require any maintenance to ensure it's working. And by permanently, I don't mean suction cups. And no long lock-line runs that can get accidently knocked lower than you plan.

Normal Operations
But normal operations, relying on siphon holes and check valves to protect your skimmer and refugium from overflowing is fine and dandy. Say you want to feed the fish and turn off the return pump. The siphon holes stop the siphon and the check valve works, water never overflow the return section. Your skimmer and fuge are fine.

 

[meemsco]

Does having 2 or 3 chambers make a difference in how much back flow the sump will hold?

 

[Quietman]

Does having 2 or 3 chambers make a difference in how much back flow the sump will hold?

I'm going to assume the chambers do not go all the way to the top of the tank so they can overflow to hold more water in an emergency.

So technically, yeah another piece of glass or acrylic will tank up more volume, but you'll never see a difference in practice.

 

[Quietman]

I'm going to assume the chambers do not go all the way to the top of the tank so they can overflow to hold more water in an emergency.

So technically, yeah another piece of glass or acrylic will tank up more volume, but you'll never see a difference in practice.

And as I think about it, a third chamber will allow a lower water level (have to be lower than first and above return) so actually an additional chamber will allow more water from backflow to be held in tank.

 

[Quietman]

Skimmer chamber at 9", Fuge at 8", Return at 6" or 7" for example. that's another 1" in the middle of volume, since you're running kind of close, that could make a difference.

But the pictures you've shown only have 2 chamber possible with the baffle design of the sock and skimmer baffle having holes in the middle.