DIY protein skimmer

[Sapper Ski]

Ok, so I’m considering building my own protein skimmer. I’ve watched a lot of YouTube, read a lot of articles, and I’m fairly handy so my confidence level in building one is fairly high.

My main concern is tank size. Nearly all of the DIY skimmers I’ve seen are on 30-40 gallon tanks. I have a 90 gallon tank with a 20 gallon sump.

For my question, I know I can increase the size of the skimmer, should I also increase the size of my pump? I have a spare 300 gph pump I was considering using, but should I go bigger? I over compensate on most everything when it comes to equipment (I have a 3,000 gph return pump that I’m honestly only using about 1/3 power).

Suggestions appreciated

 

[This guy is Extra Salty]

What materials are you going to use?

 

[theMeat]

300 gph could be good, depending on design.
What style skimmer are you thinking?
Kudos to you!

 

[Sapper Ski]

It’s going to be a Venturi style skimmer (??) (I’m not going to use an air stone as my pump has an air intake on it).
I’m going to be using clear 4” pvc if I can find it easily. Otherwise I’m just going with whatever thin 4” pvc they have at Lowe’s for the main body. 1” pvc for the collection tube and scour Walmart for a collection cup I can modify. 1/2” pvc for plumbing return line. I have a spare maxi jet 1200 pump I was intending on using.

 

[theMeat]

Clear pvc isn’t cheap but can be found online. Would think bigger than 4” would allow for easier construction of bubble plate and what not.
A pump rated for let’s say 300 gph will go down once air is introduced.
A needle wheel impeller would make a great improvement in skimmate production. Could also do a diy mesh wheel mod.
If you use a forced Venturi style pump, as you would have with your Marineland pump, the air that’s pulled in is after the pump impeller. So a needle wheel won’t help chop up and make more smaller bubbles. IMO better off using an induction style Venturi as you find on mostly all modern skimmers. With a forced Venturi as you find on older skimmers, you need a big pump, and the size of it compared to air intake size, skimmer body size is a lot bigger part of getting it dialed in to get good skimmate production

 

[Sapper Ski]

ok, questions. An induction style Venturi would mean the air is introduced before the impeller? Basically modify the pump to allow it to suck air in with the water? Or are you talking about using an air pump with a wood stone to produce the bubbles and strictly using the pump for water circulation?

 

[theMeat]

Yes, induction is air sucked in before impeller. So impeller chops up air making more, smaller bubbles. And would be easier to dial in, with skimmer body water level output valve.

 

[Sapper Ski]

So, basically I would drill a 1/4” hole for the air line on the intake (marked in silver)?

 

[Sapper Ski]

I have an air adjustment on the airline so I won’t need to make any modifications there.

 

[Sapper Ski]

My only reason for using clear pvc is so I can better see the reaction chamber. I have no experience with acrylic and trying to mold my own acrylic chamber I feel like would just cost me more in the long run.

 

[garbled]

I have a very old, precambrian era skimmer, with a solid PVC body. I have never gotten this device to work properly, because you can't tune the bubbles at all. Suddenly you just have bubbles up at the neck, and you can't tell what madness is going on underneath. This is why not a lot of people do DIY skimmers:

1. Clear PVC is tough to get in large diameters, or expensive.
2. Acrylic requires a certain amount of precision with a saw to get clean, bondable edges.
3. The pump is probably the most important part. You want a modern needle wheel with good power and some amount of adjustability. You probably want more power in the pump than you think you do, just because the bubbles eat up like half of it.

Your airline placement looks good, but I found that thin 1/8" airline tubing is kinda bad for this. I think you want bigger airline tubing, like 3/16 or 1/4". You still need the input adjustment, but definitely larger. I found I could never get 1/8" to work right in a DIY application.

 

[Sapper Ski]

@garbled
Do you feel I need a bigger pump?
Airline tubing won’t be an issue to get. My local Lowe’s has a ton of options for 1/4” flex lines if I remember correctly.

My next question:
If I would need a larger pump, would it be better to skip the airline and go with an air stone while still utilizing my current maxi jet 1200?

 

[garbled]

A good modern skimmer uses a pump with a needle wheel impeller, and an airline that pulls in right before the intake of the pump. I don't see how an airstone would work at all.

 

[Sapper Ski]

I’ve seen some built with one. But I agree, I don’t see how the air stone is really doing anything other than creating bubbles. From what I have read and seen, it’s the impact of the impeller plus the introduction of air that causes the proteins to separate and rise with the bubbles into the collection cup.

Correct me if I’m wrong.

 

[garbled]

Basically, you want alot of bubbles, alot of tiny bubbles. You want them moving around inside the body at a reasonable rate of speed. The skimmer works on two things:

1) Bubbles. Bubbles collect proteins on the surface and transport it up the neck. Tiny bubbles collect more protein usually, because of surface area.
2) Dwell, or contact time. The longer the bubble stays in the water, the more time it has to pick up protein. If a bubble simply goes straight up, it won't do much. You want it spinning around in circles picking up waste.

The reason people "tune" skimmers, is that there is a magical synergy between dwell time and bubble size and speed of pumping, and circulation that ends up with everything being just right. Too much of any one thing wrecks it. A simple column of bubbly water going up a neck into a cup will not produce results you are happy with.

 

[Sapper Ski]

Makes sense. I was going to angle the water pump at less than 45 degrees, probably closer to 25 or 30 degrees to get more of a swirl and allow more contact time with the bubbles. Thoughts?

 

[theMeat]

Like that thought
Like the thought of a bubble plate too, with skimmer output from below the bubble plate to keep micro bubbles from exiting skimmer.
Think you’re going to need a bigger pump