Questions for the UGF users

[Tanked]

I have always used UGF filters with powerheads in combination with the HOBs.  The idea being that extra filtration, aeration, and circulation is a good thing.  If I remember correctly, in one of his videos Cory mentioned that the UGF also gives the root and water column feeders the best of both worlds. 

When I put my 29 gallon back in service, I found the powerhead was too much for the small fish, so I switched to air driven.  The first question is how  much air is required to be effective?  The second would be: do tiny air stone bubbles draw more water than bubbles from an open air line?  I have no doubts about the UGF/powerhead combination., but I often wonder about how much water is actually being drawn through the gravel  by rising air bubbles.

[Zenzo]

It has been a long time since I have used UGF, but I used them exclusively in the past (20+ years ago). My understanding is that a high output from an airstone is not necessary. I don't know the fluid dynamics, but I believe that when using air, moderate to even light flow is sometimes preferred for optimal lift. As far as an airstone vs just an open airline, I believe that an airstone is preferred for a more even flow, as well as less noise from the bubbles hitting the surface.

I hope this helps. Others may have more information on this subject.

 

[lefty o]

been many years since using an ugf, but all that is need for them to work is a steady trickle of bubbles from down near the bottom of the tube. huge flow isnt required. im unsure if a higher flow is a negative, but it certainly isnt needed for an ugf to work.

[Andy's Fish Den]

It's been a long time since I have used an UGF, but from what I remember when I used it, it seemed like there was better flow with an airstone and many smaller bubbles vs. an open airline with larger bubble. I also remember, when I would get lazy and not top off tanks, or be away on vacation etc, and the water level would get down to below the elbow where the water and air escape, it seemed like with airstone and what I would call a low to moderate flow had a lot of water coming out. I could be wrong, as I am not an engineer or anything to understand fluid dynamics, but that's what I seem to remember.

[Streetwise]

I haven’t run under gravel filters since I was in high school, but I don’t think they need more than the gentle flow of a sponge filter.

[OnlyGenusCaps]

8 hours ago, Tanked said:

do tiny air stone bubbles draw more water than bubbles from an open air line?

Depends on the diameter of your air stone versus the diameter of your lift tube.  If the air stone is relatively large it can actually block some of the flow.  I saw a really good test of this somewhere on YouTube, but because it is on a video platform, it's impossible to reference back to unless you recall the exact video.  If I stumble across it again, I'll post a link here.  I suspect this is why the old Lee's air-stones had a slim profile; prevents blocking the lift tube.  So, you can get good flow even without an air-stone.  I prefer them though because the bubble sounds don't drive me nuts then. 

[Tanked]

Thank you all.  The questions are prompted by the inability to see a significant water exchange happening under normal conditions.  It makes sense that thousands of bubbles from the air stone will move more water.  It occurred to me that  even the manufacturers never mention a required volume of air.

[Tanked]

20 hours ago, Andy's Fish Den said:

the water level would get down to below the elbow where the water and air escape, it seemed like with airstone and what I would call a low to moderate flow had a lot of water coming out.

That is one of the reasons for my question.  If I drop the water level just below the top of the lift tube, I should see some water continuing to flow.  I guess some more experimentation is in order.

[HH Morant]

More and smaller bubbles move more water. That is the conclusion in a Cory video about sponge filters.