Skimmer flow rate ???

[Azederach]

Hello all. I'm a new member and have found a lot of help in the forums, but there is one question I can't answer on the internet so far.
I have a 75 gallon tank with a diy 3/4" pvc overflow and a dc pump that I have to set the controller on the lowest setting. I put the pump in a box ( as a baffle ) so that I don't run the sump dry and flood the dt in an overflow failure. This troubled me because for many years the water level in my sump could vary and the overflow keeps the display level, now I have to keep the sump level stationary as well. I am looking into adding a controller to prevent display overflow, but that's a different topic. Which brings me to my point.

The overflow isn't fast enough. I would like to put heaters in the sump and other quality of life improvements. Here's the system: the water flows into the overflow pipe at the surface, travels into the four foot by four inch skimmer (countercurrent, limewood airstone, piston air pump), then to the sump, through a sock and then to the return pump. In the sump is a dual gfo/carbon type reactor. I want to upgrade the overflow to at least one inch and add a weir, but I do not know if the increased flow will negatively affect skimmer performance. Any help would sure be appreciated.

 

[kharmaguru]

Interesting setup. The skimmer is essentially your downpipe? I've never run that type of skimmer but I would assume like all skimmers there is an optimal water/air/contact time balance and therefore there will be some performance affect - but it easily could be positive.

Here's a bump up that someone more knowledgeable might respond.

 

[mellotang]

That sounds like a complicated system

If you are increasing the flow rate through the tank then the water is going through the skimmer quicker

If the water moves too fast through the skimmer then you won’t have enough contact time to skim Efficiently

Maybe drill a hole in the skimmer, add a BH type fitting and feed it with a separate pump in the sump. Make it a recirculating skimmer

 

[Azederach]

I

Interesting setup. The skimmer is essentially your downpipe? I've never run that type of skimmer but I would assume like all skimmers there is an optimal water/air/contact time balance and therefore there will be some performance affect - but it easily could be positive.

Here's a bump up that someone more knowledgeable might respond.

Thank you. I had considered that it might be better, but unless I want to recreate my skimmer in the event it's worse I thought I'd get other views before making irreversible changes.
To answer mellotang, that suggestion has potential, but I've always thought that my benefit from this unusual arrangement is that every drop that leaves the tank gets skimmed. In fact, I don't really like that my reactor vents into the same section it draws from. One pass should be one pass. Or am I paranoid about efficiency.....Increased flow through the sump should keep pollutants at max concentration, right ?

 

[mellotang]

Maybe slightly paranoid

I understand wanting 100% raw water to enter skimmer and agree with that philosophy

What it you split the drain line, maybe half to the skimmer
Half to the sump

At least you’d then be able to handle more total tank turn over and still have all raw tank water feeding skimmer

 

[kharmaguru]

I

Thank you. I had considered that it might be better, but unless I want to recreate my skimmer in the event it's worse I thought I'd get other views before making irreversible changes.
To answer mellotang, that suggestion has potential, but I've always thought that my benefit from this unusual arrangement is that every drop that leaves the tank gets skimmed. In fact, I don't really like that my reactor vents into the same section it draws from. One pass should be one pass. Or am I paranoid about efficiency.....Increased flow through the sump should keep pollutants at max concentration, right ?

I'd love to see a picture of what this skimmer setup looks like.

 

[Azederach]

I tried, but the skimmer is behind the corner of the tank and the pipes are obscured, tank is only six inches from the wall. What it is is a four foot piece of schedule 40 (?) with a skimmer head mounted to the top on about 8 inches of 3" clear acrylic pipe (where 1" of waterline is visible when operating and where the foam concentrates), about a foot down the cpvc body the water enters from the overflow, giving several inches for concentration in the water column. at the bottom it exits, travelling up a 3/4" pipe to the water level to two 90 degree connectors (u bend) with a 1/8" tube mounted vertically into it (about four inches, above the waterline) as an air gap to prevent 'flushing' then down to the sump. It's driven by a piston air pump through a limewood stone threaded down from the top. I'll try to get a better angle of it tomorrow.

 

[BeanAnimal]

See if this helps

6 Foot Tall DIY Protein Skimmer | BeanAnimal's Reef

DIY 6 foot tall (7 with collection cup) protein skimmer for a reef aquarium. Constructed with acrylic and clear PVC. Full construction details and image gallery.

beananimal.com

From what you describe, you have a lot of variables to work with. It will skim, but will not be super efficient and not be easy to keep dialed in.

I removed the recirc needlewheel from the 6' skimmer and went with ultra fine ceramics. More reliable than limewood.

Feeding directly from the surface skimmer/overflow is in theory the best, but will make things hard to keep dialed in, unless you convert this to a recirculating design which may not be worth the effort.

The skimmer worked extremely well - but it took a year or two of trial and error. It ran for 5+ years maybe more until I took it offline to dabble with turf scrubber only export.

I would NEVER DIY another skimmer. I just ordered a Reef Octopus to save myself the hassle.

Are you hellbent on a DIY, constrained by budget, etc?

 

[Azederach]

See if this helps

6 Foot Tall DIY Protein Skimmer | BeanAnimal's Reef

DIY 6 foot tall (7 with collection cup) protein skimmer for a reef aquarium. Constructed with acrylic and clear PVC. Full construction details and image gallery.

beananimal.com

From what you describe, you have a lot of variables to work with. It will skim, but will not be super efficient and not be easy to keep dialed in.

I removed the recirc needlewheel from the 6' skimmer and went with ultra fine ceramics. More reliable than limewood.

Feeding directly from the surface skimmer/overflow is in theory the best, but will make things hard to keep dialed in, unless you convert this to a recirculating design which may not be worth the effort.

The skimmer worked extremely well - but it took a year or two of trial and error. It ran for 5+ years maybe more until I took it offline to dabble with turf scrubber only export.

I would NEVER DIY another skimmer. I just ordered a Reef Octopus to save myself the hassle.

Are you hellbent on a DIY, constrained by budget, etc?

Oh, it's one part shoestring budget and one part tired of small fiddly skimmers. I wanted it to skim all of the water and do it for a long contact time and be pretty much industrial in scale. I was out of town for the weekend, I'll try to get some pics of it soon, I think I will put a valve on it and upgrade the overflow to a one inch pipe. It's output is already one inch. Then I can tweak it and we can find out what's possible with it.

 

[Azederach]

Oh, it's one part shoestring budget and one part tired of small fiddly skimmers. I wanted it to skim all of the water and do it for a long contact time and be pretty much industrial in scale. I was out of town for the weekend, I'll try to get some pics of it soon, I think I will put a valve on it and upgrade the overflow to a one inch pipe. It's output is already one inch. Then I can tweak it and we can find out what's possible with it. I might also consider having the skimmer run parallel to the sump system.

 

[BeanAnimal]

The skimmer was a fun project. While it ran and skimmed on day 1, it took a lot of tweaking to get right. I think you have too many things working against you to make this work reliably.

I just put a Reef Octopus online and it I am sad that I didn't do this 10 years ago! It was easy to setup, is clearly very efficient and stable.

 

[Azederach]

Good suggestions, thank you all. Mainly I was hoping someone had some equations for skimmer height, diameter and flow rate.

 

[kharmaguru]

Some light reading, lol.

The Development of a Method for the Quantitative Evaluation of Protein Skimmer Performance

 

[BeanAnimal]

There are equations - they are by and large, useless.

You can find them in Aquatic Ecosystems Engineering by P.R. Escobal

Increasing your flow rate will reduce your contact time, no matter what size you make the skimmer body. Higher contact time = better performance.

Rules of thumb for "sump througput" are also pretty much useless anecdote passed from one reefer to the next and mean nothing without context.

Heaters - Is there enough turnover to keep the display at the same temp as the sump? If so, then you have enough flow.

Flooding - Limiting the return pumps available volume fixes one issue and creates another that you have already realized. You have no room for evaporation and need an Auto Top Off.

I will say that if you do add a float switch to "turn off" the return pump if the display level gets too high, you need to have setup as a latching circuit to keep the pump off until manually reset. Otherwise the float will trigger, the pump will turn off and as the water drains back into the aquarium the float in the display will turn it back on. Over and over until the return pump burns up.

I am still not fully sure if your need to build the skimmer. A $200 or so Hang On Back or in-sump skimmer will outperform your DIY skimmer many times over.

 

[BeanAnimal]

Some light reading, lol.

The Development of a Method for the Quantitative Evaluation of Protein Skimmer Performance

Ohh the memories of the science of "foam fractionation" and the calculations is they relate to flow, air volume and bubble size, turbulence, etc.

I was sent to rehab, and now buy things instead of always trying to build them!

 

[Azederach]

There are equations - they are by and large, useless.

You can find them in Aquatic Ecosystems Engineering by P.R. Escobal

Increasing your flow rate will reduce your contact time, no matter what size you make the skimmer body. Higher contact time = better performance.

Rules of thumb for "sump througput" are also pretty much useless anecdote passed from one reefer to the next and mean nothing without context.

Heaters - Is there enough turnover to keep the display at the same temp as the sump? If so, then you have enough flow.

Flooding - Limiting the return pumps available volume fixes one issue and creates another that you have already realized. You have no room for evaporation and need an Auto Top Off.

I will say that if you do add a float switch to "turn off" the return pump if the display level gets too high, you need to have setup as a latching circuit to keep the pump off until manually reset. Otherwise the float will trigger, the pump will turn off and as the water drains back into the aquarium the float in the display will turn it back on. Over and over until the return pump burns up.

I am still not fully sure if your need to build the skimmer. A $200 or so Hang On Back or in-sump skimmer will outperform your DIY skimmer many times over.

I'm considering putting a well regarded skimmer in the sump in competition with my current one to test how much my diy may be missing. If it outperforms then I know I can remove it. I currently get roughly a quarter cup of dark green sludge per day, and if it sits it gels. I have a very long foam concentration chamber and very little load.

 

[mellotang]

If it’s working then why are you
Looking to mess with it?

 

[mellotang]

Put heater in aquarium and be done with it

 

[Azederach]

Put heater in aquarium and be done with it

I've always had the heater in the tank, I don't mind that, but when I built a new stand and reset the tank I went from a ten gallon sump that's only purpose was to let me run the skimmer and keep the water level in the tank constant to a 29 gallon sump that I can do more with, so I added a filter sock and a gfo/purigen reactor and a dc pump because the cascade canister filter I was using as a lift pump was unreliable. Now I'm restricting the pump on it's lowest setting and see a chance to process more water.

 

[Crowed]

Why you said that overflow is not fast enough? you actually do not need fast water flow trough sump.. Your skimmer would probably work worse, less contact time but also more flow bring more turbulences what lower perfomances, especialy in 4 inch diameter body