# new idea for undergravel filter?



## racerx (Sep 30, 2012)

Im new to posting so I think I posted this as a reply to someone else's thread earlier, so I appologize for if you've already seen this. I have been out of the fish scene for about 17 years, and alot of things have changed. I just started up a 36 gallon bow front and insisted on undergravel filtration. I discovered this forum (You all have taught me so much just by reading through other threads) and see where this type of filter has pros and cons. Here is my experiment: I made a reverse flow powerhead out of a standard powerhead, a couple of o-rings,and repositioning the head over the uplift tube. Since bacteria need O2, I partially opened the air valve to shoot air into the downlift tube resulting in a bit of air bubbles escaping through the gravel bed. I would thimk this a nice system,but I would appreciate some feedback. I'm also running an Aqueon 55 power filter, and a Marineland 150 Bio-Wheel.
Would appreciate any and all comments,suggestions,critiques,etc.

Thanks


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## Freshcatch (Aug 8, 2012)

Welcome to the forum. Can you show us a picture or diagram of your filter system. I think I understand where you are going with this, but it would help if we could see it.


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## racerx (Sep 30, 2012)

Freshcatch said:


> Welcome to the forum. Can you show us a picture or diagram of your filter system. I think I understand where you are going with this, but it would help if we could see it.


 having problems downloading pics, but what I did was pull the flow deflector off the output of the powerhead, install a couple of O-rings around the shaft and turned it so the output went down the uplift tube. I then set the air diffuser to light aeriation so it shoots small stream of air bubbles under the filter plenum which comes out at various places in the gravel


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## Tazman (Jan 15, 2012)

Basically by the sound of things you have create an undergravel jet system rather than a filter. Having the flow rate too high will not give any detritus (waste) time to be in contact with the bacteria long enough for it to be broken down.

Undergravel filters are not really used anymore as they clog easily, need more maintenance, can be nitrate trap and if anything goes wrong with them, you have to rip the tank apart to fix them.


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## AbbeysDad (Mar 28, 2011)

Reverse flow undergravel filters are old school now and there are kits to convert regular UGF's to reverse flow. Oxygen in the water is the result of moving surface water or when bubbles break the surface and a CO2/O2 gas exchange occurs....so adding an inline air line in the flow tubes is really counter productive.

Taz is correct in that beneficial bacteria are somewhat opportunistic feeders and slower moving water is processed much more productively. Airflow in the standard UGF moves water slowly through the gravel bed.

Although I've used them in the past, I'm not a fan of UGF regardless of flow direction (although reverse flow is probably less problematic than regular UGF).
The trouble is with the gravel as even with reverse flow, too much waste and uneaten food sifts down into the gravel where it decays and produces copious amounts of ammonia...nitrites...nitrates. This requires routine gravel siphoning.
I converted to [deep] sand some time ago. Mulm collects on the surface and slowly decays or can be easily removed and the sand is an excellent bio-filter. 

Just my $.02. If you move forward, hope it works for you.


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## racerx (Sep 30, 2012)

AbbeysDad said:


> Reverse flow undergravel filters are old school now and there are kits to convert regular UGF's to reverse flow. Oxygen in the water is the result of moving surface water or when bubbles break the surface and a CO2/O2 gas exchange occurs....so adding an inline air line in the flow tubes is really counter productive.
> 
> Taz is correct in that beneficial bacteria are somewhat opportunistic feeders and slower moving water is processed much more productively. Airflow in the standard UGF moves water slowly through the gravel bed.
> 
> ...


 and to think I thought I was onto something different. However there are bubbles at various places breaking the surface of the water,along with the flow from both powerheads. There is also a traditional air stone with air pump working in the other uplift tube. Not really wanting to tear down tank to remove filter, but I have been reading alot of negatives here about ugf. I had quite a few tanks years ago with ugf and never had problems (that I can remember), but the times they are a changin


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## AbbeysDad (Mar 28, 2011)

racerx said:


> ... but I have been reading alot of negatives here about ugf. I had quite a few tanks years ago with ugf and never had problems (that I can remember), but the times they are a changin


I also used them in the 70's - they were a very economical bio filter, long before there was the bio-media there is today. They were effective, but could get nasty in time and did present a risk if there was ever a power faliure allowing anaerobic bacteria to take over and quickly foul a tank.
So UGF still works....but we have much better options today.


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## racerx (Sep 30, 2012)

AbbeysDad said:


> I also used them in the 70's - they were a very economical bio filter, long before there was the bio-media there is today. They were effective, but could get nasty in time and did present a risk if there was ever a power faliure allowing anaerobic bacteria to take over and quickly foul a tank.
> So UGF still works....but we have much better options today.


Ok. After much thought and reading, I removed the UGF today. I did leave one plate 2"X4" in a corner to run the reverse flow powerhead with aeriation on uplift tube for sporatic bubbles in the gravel. Looks kinda neat and gets air in the gravel. Thanks for all the advice, I'm sure this wont be last time


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