Noisy RFUGF?

ghost_shrimp

ghost_shrimp

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Apr 18, 2004
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Silicon Valley, CA
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I converted my 40g with a conventional undergravel filter to a RFUGF with 2 Penguin 660R Powerheads. The problem is that when I start them up, I hear the gravel rattling around underneath the filter plate. The noise is right next to the lift tube and it doesn't sound like the gravel is being pushed around, just moving around in the same area.

Has anyone else had this problem? Currently I only have about half an inch of gravel on top of the filter. Do I need more substrate? Could it be that the filter plate isn't flush on the bottom of the tank and I'm pushing more and more gravel underneath the plate? Any help would be appreciated.
 
I had the same set-up a few years back. Sometimes the Penquin powerhead had air in it. It would make a terrible racket sounding like rocks or something. I would have to remove it from the elbow that connects to the UGF and turn the powerhead upward so the air could be released. Then I would put it back and it would be good to go for a while. Anytime the water level fall below the height of the powerhead (after water changes), I had to do this.
 
I had the same set-up a few years back. Sometimes the Penquin powerhead had air in it. It would make a terrible racket sounding like rocks or something. I would have to remove it from the elbow that connects to the UGF and turn the powerhead upward so the air could be released. Then I would put it back and it would be good to go for a while. Anytime the water level fall below the height of the powerhead (after water changes), I had to do this.
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I would guess this is your problem as well. take out the plug on the output nozzle of the powerhead (where the venturi tube is designed to attach). most of the time it will dispell the air, if not you will definately have to do as instructed and pull the powerhead back and tilt it. The smaller penguins seem prone to airlock, and create a massive racket when they have air in them.
dave
 
I'd guess this is my problem too.

I had unplugged them to stop the noise and intended to look into the cause when I had more time..

Then the tank started to leak so the noise was the least of my problems.

anyway, amazing what you learn if you just lurk.. I should have my replacement tank on Tuesday.

Thanks Left C and Daveedka
 
I'm still hearing the rattling noise. I followed all the advice to get all of the air out of the powerhead, but I don't think that's the problem. I can tell the noise is coming from the bottom of the tank underneath the gravel. I'll add some more gravel to the bottom and hopefully that will slow down the flow a little underneath the plate. Thanks for the suggestions.
 
ghost_shrimp said:
I'm still hearing the rattling noise. I followed all the advice to get all of the air out of the powerhead, but I don't think that's the problem. I can tell the noise is coming from the bottom of the tank underneath the gravel. I'll add some more gravel to the bottom and hopefully that will slow down the flow a little underneath the plate. Thanks for the suggestions.
Click to expand...

I used to be able to crawl under my aquarium stand and see the bottom of the underground filter plate. Is there any way you can do this? You'd see gravel moving and banging on something if the noise was there. If you don't see anything, either your impeller is broken or you still have air in it somewhere. The only moving part is the impeller. When you loosened the powerhead, was it still running and did you see bubbles escape? If you didn't have it running, you might not of gotten all the air out. You might have to rotate it around a little to get all of the air out. Just removing the plug, as mentioned above, wasn't enough to get the air out. You had to remove it from the elbow connection. I remember this problem well. I even called Marineland and told them they had defective impellers on their 660R powerheads (I had three) when all along it was just the air trapped inside it.

Something else, you should trash your RFUG any way. The idea is sound enough, but what you end up with is a nitrate pump. Not only do you have bacteria that changes ammonia and nitrite to nitrate on the surface of the gravel, you have the same mechanism on the bottom now plus a little more in the middle of the substrate too. You then have no mechanism for anaerobic bacteria to form and turn the nitrate into nitrogen gas. If you continue to use it, you'll have high nitrate levels that no amount of water changes can correct!
 
There are plenty of 'dead spots' in a RFUGF for anerobic bacterial action. Nitrate levels have to be pretty high to adversly affect fish. Excess nitrate will flow through the gravel into the water column and if decent water changes are done weekly, then no significant buildup will occur. Interesting info though. I have never heard of the beneficial effect of anerobic bacteria before, only the adverse effects of anerobic bacteria. Do you know of a site that can explain it in more detail?
 
The concept of an anerobic RFUG is mind-boggling. I have never experienced such, how exactly are there "plenty of anaerobic spots"? Was the RFUG not prefiltered and so became dirt-loaded?

Nitrate pump? What else exactly is a biological filter supposed to be? Biofilters oxidize ammonia through nitrite to nitrate. That is their job. Do you think that they should not do this?

If you build in a FW plenum you can get denitrification if you do it right, but a deep gravel or sand bed alone is more risk of overshooting the denitrifiaction ORP and getting down to the sulfur and iron reducing ORP levels where I do not want my tanks to go. No thanks, NIMFT.
 
Guess I was wrong about the 'dead spots' in the RFUGF. I was reffering to the places where the UGF plate doesn't reach the sides of the tank.
 
Update: Unfortunately, I have an acrylic aquarium, so I can't look underneath and see what's the problem. So I put the narrow end of my gravel vacuum down the uplift tube and tried to suck out the loose gravel from underneath the filter plate. But then I noticed the surface gravel surrounding the uplift tube being sucked down. That must mean that my undergravel plate isn't sitting flush on the bottom of the aquarium and when I turn on the powerhead, it draws the gravel along the edges of the plate underneath it.

So now it looks like my options are now to break down my tank and make sure the undergravel plate is seated correctly, or just remove it completely and go only with my HOB Aquaclear. I had planned to run both in tandem. :sad:
 
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