Skimmer vs Reactor: Water Level Physics

[MantisShrimpMan]

I know with internal protein skimmers that the height they sit at in your water makes a massive difference on their effectiveness and the consistency of their skim mate. While it's been a while since I watched all the videos online on the matter, my general understanding is that this is due to the difference in height of ambient pressure change and how that affects the gas bubbles that are being pushed up through the skimmer cone. Hence why hang on rim or magnet on back skimmers like the bubble magus mini Q can have their height adjusted, and why people buy or make stands to keep their skimmer at the right height in a sump.

So, I am curious if the same applies to reactors, and if so, if it does it to the same effect. I know this also coincides, to some extent, with the physics of head pressure loss on submersible pumps. Take these different non-skimmer forms of filtration:

All three of these have submerged pumps feeding the filtration equipment, the body of which rises above the water level. So my question is whether the flow through these has as much of an emphasis on correct water height or not. Like, I'm planing out a current build and was wondering if I could use that UV sterilizer in an AIO return chamber. Sure, the water height in the return chamber will be less than in the central/skimmer chamber, but I'd imagine as long as the pump itself is still submerged, it still has the ability to push water up the tube regardless of the tube's height above water surface? Or am I missing something?

 

[Dan_P]

I know with internal protein skimmers that the height they sit at in your water makes a massive difference on their effectiveness and the consistency of their skim mate. While it's been a while since I watched all the videos online on the matter, my general understanding is that this is due to the difference in height of ambient pressure change and how that affects the gas bubbles that are being pushed up through the skimmer cone. Hence why hang on rim or magnet on back skimmers like the bubble magus mini Q can have their height adjusted, and why people buy or make stands to keep their skimmer at the right height in a sump.

The water height determines what type of foam is pushed up the skimmer neck. A weak, fragile foam will not rise up the skimmer neck. Instead, the head breaks and the skimmer collects nothing. Increase the water height and the weak head is able to reach the top of the skimmer throat. When the foam is strong, it can travel a long way before collapsing. A lower water height is needed for this quality of foam to find its way out.

 

[jda]

The strength of the pump and the size of the bubbles matters too. In older skimmers where they had actually powerful pumps, the sump level was not very important since the pump could handle any head pressure without degrading performance. Non-uniform bubble sizes can help too where the larger bubbles push the smaller ones up and out. Anbybody who has used a downdraft, beckett or good venturi skimmer can just watch the foam rise up with the larger, non-uniform bubbles that they have.

In most cases, if the water level has to be perfect, they are using a skimmer with a weak pump trying to maximize air. You need some power too. The blend of power and air is important, IMO.

 

[MantisShrimpMan]

@Dan_P @jda

So does this mean that, when air isn’t involved like in a media reactor, mounting height doesn’t matter? That’s what I’m really asking

 

[jda]

Closed systems do not have any head pressure except for where the entry and exit is. The head that you lose pumping up is made up for by gravity/siphon coming down.

Of course, there are friction and other losses.

 

[twentyleagues]

Water height over the pump will affect it ability to pump water also. Less water over the pump the pump will be less "efficient" but shouldnt effect overall performance that much. It does make a difference though.

 

[MantisShrimpMan]

@jda @twentyleagues

So, do you guys think it would be okay to mount the UV sterilizer I showed in the return chamber?

 

[twentyleagues]

@jda @twentyleagues

So, do you guys think it would be okay to mount the UV sterilizer I showed in the return chamber?

It should be fine.