Skimmer experts please advise and check my logic

PedroYoung · Sep 16, 2022

I've been running a Vertex Alpha 200 skimmer for about 4 yrs and have never really gotten it tuned the way I want (dryish skimmate). I have a 200G tank, with pretty decent fish load (3 pyramid butterflies, borbonius athais, 3 bimac anthias, 2 yellow tangs, blonde naso tang, kole tang and mandarin). They also are fed pretty heavily via @AVAST Marine Plank autofeeder 2x day and manual frozen medley once per day, plus a variety of seaweed sheets. There are basically 3 variables I have to work with
1- Sump level
2- Wedge pipe
3- Pump intake nozzle

I've always assumed I understood how adjusting each of those 3 variable would change skimmer output, but man it seems like it just never does what I expect. Here are some pics of the setup. (this pic shows the carbon reactor running, but I only run it about 3 weeks every 3 months or so, currently out of service)

Untitled by Peter Young, on Flickr

and pump with intake nozzle

Untitled by Peter Young, on Flickr

So I'll address each of these variable, give my assumption, and if I'm wrong, PLEASE let me know
1- Sump level. This is the one I haven't really tinkered with. Designed to run at 10" depth, I run at 9" (I can adjust this by simply adding some more water to the system and raising the baffle). My assumption has always been that deeper depth (say 10" instead of 9") would lead to more bubble ejecting up the neck, leading to more water/less organics and wetter skimmate.

2- Wedge pipe. I've always assumed (sometimes tested) that a wide open wedge pipe (opening in the wedge facing the outlet) would lead to less water/ more organics in the collection cup.

3- pump intake nozzle. This one is really poorly explained in the "manual" and has been through a series of tests that always leave me more confused than when I began. Unscrewing the nozzle seems to lower the level of bubbles in the chamber. If opened too far, bubble come out of the skimmer output.

Right now I'm going through a skimmer cup a day, and when it fills up saltwater bubbles blow out the top and make a huge mess. Real pain. If anyone has any insight I'd LOVE to hear it.

Thanks.

P

Also, feeding vid here just for stopping by

T-J · Sep 16, 2022

Here's the manual for your skimmer. Not sure if you've looked it over recently.
I'd get the water level where the skimmer is to 9.5", as the manual says 9-10" for proper skimming.

http://cdn.bulkreefsupply.com/media/wysiwyg/PDFs/Vertex%20Alpha.pdf

PedroYoung · Sep 16, 2022

Haha, yeah I keep the manual right next to the sump cause I always think I'm going to see something else in it that would make sense. I guess I just don't understand the hydrodynamics of the water level in the skimmer and how it changes what's happening in the collection cup. It's what I've decided to do next, but would love to understand the "why".

PedroYoung · Sep 17, 2022

Kodski · Sep 18, 2022

I'm going to try to help but I highly recommend you go watch the BRS how to tune your skimmer series. I think those videos will really help you. I know I've watched them several times to better help my understanding of skimming.

So if I understand correctly, you're currently skimming quite wet and your goal is to skim on the dry side. If you watch BRS' videos on skimming, their tests showed that changing water height did little on the outcome of a wetter or dryer skim. Instead they found that more or less air had the largest effect on the type of skim produced. More air = drying skimmate and less air = wetter skimmate. Judging from how you've explained how you think your skimmer tuning works, you've dialed back on what you called your "pump intake" trying to get the bubbles further down the neck. In reality what you're doing by closing the pump intake, is reducing the air draw into the skimmer, which is exactly the opposite of what you want to do if your goal is a dryer skimmate.

This is where my personal experience ends though, as I have a recirculating skimmer so my wedge pipe (its actually a gate valve) has a slightly different effect and I'm not sure how applicable my experience is to your skimmer. In my situation, my gate valve does allow me to dial in the water height inside the body of the skimmer. Since I have a separate pump to pump water into the skimmer and a different pump to produce bubbles, that is the soul function of the gate valve. In your case, you have one pump producing bubbles as well as pumping water into the skimmer. So when you close your wedge pipe, it would technically raising the water level inside the skimmer, but it would also be increasing the dwell time of the water inside the skimmer. For me to vary the dwell time of the water inside the skimmer, I would just adjust the feed pump flow rate up or down. Hopefully this makes sense. I believe this to be the most difficult part to dial in for a skimmer like yours as its dependent on many factors, sump water height, bioload, ect.

As for overall water height, I believe as T-J said your best best is to shoot in the middle of the recommended water height as a starting point. Some skimmer designs require the water height to add "back pressure" to the output which helps to reduce microbubbles escaping the skimmer. This might be why you have micro bubbles when opening the air intake up.

If it were me this would be my process. Set sump water height to 9.5" and fully open wedge pipe and air intake to the pump. See what kind of results that produces and adjust from there. If the skimmate is still too wet, the simple answer might be that you just have too much bioload for the skimmer to produce a dry skimmate. A larger skimmer with a larger air draw would then be the solution. IMO, I'd say your skimmer is undersized, so this very well might be the case here.

PedroYoung · Sep 18, 2022

Kodski said:
I'm going to try to help but I highly recommend you go watch the BRS how to tune your skimmer series. I think those videos will really help you. I know I've watched them several times to better help my understanding of skimming.

So if I understand correctly, you're currently skimming quite wet and your goal is to skim on the dry side. If you watch BRS' videos on skimming, their tests showed that changing water height did little on the outcome of a wetter or dryer skim. Instead they found that more or less air had the largest effect on the type of skim produced. More air = drying skimmate and less air = wetter skimmate. Judging from how you've explained how you think your skimmer tuning works, you've dialed back on what you called your "pump intake" trying to get the bubbles further down the neck. In reality what you're doing by closing the pump intake, is reducing the air draw into the skimmer, which is exactly the opposite of what you want to do if your goal is a dryer skimmate.

This is where my personal experience ends though, as I have a recirculating skimmer so my wedge pipe (its actually a gate valve) has a slightly different effect and I'm not sure how applicable my experience is to your skimmer. In my situation, my gate valve does allow me to dial in the water height inside the body of the skimmer. Since I have a separate pump to pump water into the skimmer and a different pump to produce bubbles, that is the soul function of the gate valve. In your case, you have one pump producing bubbles as well as pumping water into the skimmer. So when you close your wedge pipe, it would technically raising the water level inside the skimmer, but it would also be increasing the dwell time of the water inside the skimmer. For me to vary the dwell time of the water inside the skimmer, I would just adjust the feed pump flow rate up or down. Hopefully this makes sense. I believe this to be the most difficult part to dial in for a skimmer like yours as its dependent on many factors, sump water height, bioload, ect.

As for overall water height, I believe as T-J said your best best is to shoot in the middle of the recommended water height as a starting point. Some skimmer designs require the water height to add "back pressure" to the output which helps to reduce microbubbles escaping the skimmer. This might be why you have micro bubbles when opening the air intake up.

If it were me this would be my process. Set sump water height to 9.5" and fully open wedge pipe and air intake to the pump. See what kind of results that produces and adjust from there. If the skimmate is still too wet, the simple answer might be that you just have too much bioload for the skimmer to produce a dry skimmate. A larger skimmer with a larger air draw would then be the solution. IMO, I'd say your skimmer is undersized, so this very well might be the case here.

Thanks for the comprehensive analysis, I appreciate it. @T-J above put the link to my manual which I had printed off years ago. To save paper I must not have printed off the “trouble shooting” section. One thing for skimmer overflowing was to check the muffler and intake line for clogs. I did that and found several flies in the muffler (go figure). Took it apart, rinsed and dried it and that seems to have helped some (restoring full airflow). I am still going to raise the sump level 1/2” and monitor what happens. Thanks for the input, I was about to watch those BRS vids again, they had one specifically about testing different sump levels with different skimmers.