Undergravel filters (Need advice and your thoughts)

[CHOMPERS]

Ok, I'll agree that air will move water and does work (I used it for years)..but this is MFK and I was leaning towards the Monster side....

Go Monster or go home


I love my lift tubes and I also have power heads. The flow is going to be dependent on the model of the powerhead, so power heads can win. A giant plus for powerheads is that they are quieter. The draw back is my two small powerheads draw over twice the power of the air pump that can do the same job.

 

[spiff]

How lift tubes work is by a difference in density (weight of the water) inside the tube and out. The less dense water/air mixture will rise in the tube because it "floats" in the more dense "pure water". The greater the difference in the densities, the more boyant the lesser will be. The density of the water inside the tube is the average of the waters density and the air in the bubbles. Small bubbles are more prone to suspend in water than larger ones. Large bubbles from an open air tube tend to slip through the water, leaving the water behind. (The water actually pours down around the bubble.) The smaller the bubble, the slower it will rise. With the smaller bubbles suspended in the water instead of slipping through it, more of the air can be averaged into the density of the water.

This theory is sound, but I don't think it covers all variables. Mainly, with big enough bubbles that completely fill the pickup tube, huge sections of water is lifted at a time that has nothing to do with air/water densities. This works more like an elevator, with a huge tube-blocking bubble providing lift, not just a bunch together causing an upward current.

But I'm no scientist either. I'm just going by testing that I have done. If the height above the water level is in indicator of water volume moved, then I have found that water can be lifted higher open hosed than with airstones. I have used both the little green round ones that fit down those tubes and the air defuser that normally comes with an UGF. Neither worked as well as going open hose.

But I have to admit the main reason for going open hose is just the simplicity. I got tired of changing air stones.

 

[Knowdafish]

UG's with powerheads rock!

 

[spiff]

Go Monster or go home


I love my lift tubes and I also have power heads. The flow is going to be dependent on the model of the powerhead, so power heads can win. A giant plus for powerheads is that they are quieter. The draw back is my two small powerheads draw over twice the power of the air pump that can do the same job.

It makes me wonder if this high-flow combo is what makes peoples UGF clog.

 

[CHOMPERS]

This theory is sound, but I don't think it covers all variables. Mainly, with big enough bubbles that completely fill the pickup tube, huge sections of water is lifted at a time that has nothing to do with air/water densities. This works more like an elevator, with a huge tube-blocking bubble providing lift, not just a bunch together causing an upward current.

But I'm no scientist either. I'm just going by testing that I have done. If the height above the water level is in indicator of water volume moved, then I have found that water can be lifted higher open hosed than with airstones. I have used both the little green round ones that fit down those tubes and the air defuser that normally comes with an UGF. Neither worked as well as going open hose.

But I have to admit the main reason for going open hose is just the simplicity. I got tired of changing air stones.

I'm not crazy about changing air stones either. I got a different result though, which is why I still use them. It's possible that the resistance of the airstones reduced the total amount of air you were getting, so you got less water flow. I use the cheap blue air stones from Petsmart, but they flow really well when they are new. When they start filling up, I get less flow than I would running them open.

 

[CHOMPERS]

But I'm no scientist either. I'm just going by testing that I have done.

By the way, you are a better scientist than most people. Most people don't think enough for themselves to do their own tests.

 

[CHOMPERS]

It makes me wonder if this high-flow combo is what makes peoples UGF clog.

If you mean 'clog' as in sucking stuff through the gravel so that it can't be vaccuumed out, that is pretty much what I was thinking. It sounds about right.

A power head in reverse mode will push gunk up to keep the gravel clean, so it seems right that in normal mode it would pull it through.

 

[tcarswell]

So im probably best off with just the airstones then correct?

 

[Knowdafish]

Note....."clogged" airstones can be unclogged by soaking in a bleach/water solution

 

[Merbeast]

You will do just fine with air stones. Walk into any fish store and you will see them doing their job. UGFs work just fine.