# Whatever happened to Under Gravel Filters ?



## RichardJW (12 Nov 2013)

30 years ago the height of Hi-tech in a planted aquarium was to have a bed of plates under the gravel which were connected to your external filter or more usually air driven via uplifts  . The theory being that like a sewage works the gravel bed acted as a huge surface area bacterial bed - the problem being in a heavy use setup ( if neglected ) it became blocked and possibly anaerobic. Move on another 10 years and we reversed the flow so it was filtered first via a canister and then passed through the gravel bed . It always worked well for me but seemed to pass into history with the advent of new generation of externals with specialised filter media . I notice that they are still available and generate controversy for reasons stated above - but, there is no mention of reversing the flow .

With all the talk of even supply of nutrients to the root zone are there any benefits to this reverse flow approach ??


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## Samuran (12 Nov 2013)

I still use one on my betta tank! and have done on various breeding tanks. (in the old fashioned air lift way)


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## foxfish (12 Nov 2013)

I cant ever remember UGs being part of high tech planted tanks, I can remember that 30 years ago heating cables under the gravel were essential though! 
It was at one time generally believed that pulling water over plant roots would effect growth or even kill the plants but it seems this is not so!
I have often though that an under gravel style of distributing the C02 would be the best way to get an even amount of gas throughout the water column, & it has been tried by Hoppy on another form & by me on this forum but, the results were inconclusive.
I am very keen to try this again though.....


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## RichardJW (12 Nov 2013)

30 years ago don't really think anything was Hi-tech ! Doing water changes was seen as a bit radical by some . 
I'm guessing for it to be useful in a planted setup a gentle movement only would suffice .


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## foxfish (12 Nov 2013)

30 years ago I had a 100 gal tank with 6 x T8s, C02 injection, heating cable & daily ferts, 20% a week rain water change.
My tank was standard Dupla set up, using all their equipment but Dennerle were also around at that time.


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## foxfish (12 Nov 2013)

RichardJW said:


> 30 years ago don't really think anything was Hi-tech ! Doing water changes was seen as a bit radical by some .
> I'm guessing for it to be useful in a planted setup a gentle movement only would suffice .


 Ah well there is a question! if we could feed the gas into a UGF & it effectively & equally raised up through the substrate then perhaps the high flow would still be there but in a very diffused way. we are used to blasting the contents of our tanks with high flow spray bars & the like in an attempt to get the C02 every where but, maybe a UGF would do a better job or maybe we would still have to supplement the UGF flow?


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## Samjpikey (12 Nov 2013)

Have you got any pics of your latest tanks foxfish ?? 
I would be keen to take a look  
You should own a masterpiece I thinks  


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## foxfish (12 Nov 2013)

Sorry Sam, I am in the proses of a complete house renovation so all I have is 4 immersed projects , my lounge tank & a reef tank but they are in the garage just ticking over.
I have a few spectacular tanks that I maintain for private costumers but I cant really post photos of those!
However in a few weeks I will getting all my tanks back on line...


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## RichardJW (12 Nov 2013)

Interesting feedback Foxfish ! In these days of information overload everybody has access to a broad spectrum of knowledge whereas even 20 yrs ago your main source of info was LFS and local hobbyists . Interestingly , your local knowledge sources must have been more forward thinking whereas mine weren't.
I would guess on the other subject that some additional flow would be beneficial as most of the plants used probably ' appreciate a bit of movement . Just like trees need a bit of wind to encourage their root system I'm guessing a slight current would have a similar effect .
Good luck with your house renovation - you have admiration , my missus doesn't even like tradesmen around even for minor jobs . I get them done when she goes off for a week with her chums !


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## foxfish (12 Nov 2013)

Yeah well we are pretty fed up with all the dust & tea making mate LOL
Re the flow...perhaps but the early tanks were very low flow designs & it seems to me there were far less problems 30 years ago than now..OK we couldn't grow a carpet of micro leaf plants but our tanks were full of colour & easy to keep...make you wonder sometimes!


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## RichardJW (12 Nov 2013)

Interesting you comment on the colours ! Some of the staples of the industry Tiger barbs , Rosy barbs are certainly not as big or bright as the early stock - I remember Rosy barbs the size of goldfish .The other old school staple were Swordtails and Platties ,which were a lot bigger and varied in colour variations .I think with commercial breeding the size and colour has slowly disappeared , maybe we need a bit of vigour re-introduced to breeding programmes . I already think the Neon praecox Rainbow is already a shadow of the original import .
It's interesting that various wild Angelfish are becoming available ,again whether they can be bred with some of the fancy varieties to produce quality fish would be an interesting development . Who remembers the Gold, Half-black and Black Veil-tails the size of dinner plates ?


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## foxfish (12 Nov 2013)

I can remember when kuhli loaches were a foot long 
I think the plants were vibrant because we kept Dutch style  tanks with lots of stems.


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## RichardJW (12 Nov 2013)

Remember them well , think they must've been on steroids ! Even the online resources only have them growing to 4" but I do remember having one the size and thickness of a Sharpie pen - also in many different colour ways . Don't think they'd be comparable with a planted setup though .


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## foxfish (12 Nov 2013)

kuhli loach = great in a planted tank you just don't see them.


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## RichardJW (12 Nov 2013)

You would if they were a foot long !!


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## foxfish (12 Nov 2013)

There is a great thread about them but I cant get on with the search button... drives me mad searching on this forum grrr.


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## RichardJW (12 Nov 2013)

Is this what you're looking for ???

Kuhli loaches. | UK Aquatic Plant Society


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## ceg4048 (13 Nov 2013)

RichardJW said:


> With all the talk of even supply of nutrients to the root zone are there any benefits to this reverse flow approach


Plants really do not care about even supply of nutrients to roots. In aquatic sediments osmotic forces, as well as Nitrogen cycle products distribute nutrients. Evenness is not relevant. Above the sediment the leaves are capable of doing the lion's share of nutrient collection and they send Oxygen down to the roots. There is plenty of movement and activity in the sediment without any need for flow supplementation. The critical area for flow is above the sediment where the leaves have limited access to nutrients and CO2. The effluent of an UG filter breaks the surface and will have the tendency to out-gas the CO2 and Oxygen.

Cheers,


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## foxfish (14 Nov 2013)

Hi mate I am not sure what you mean by "The effluent of an UG filter breaks the surface and will have the tendency to out-gas the CO2 and Oxygen." but I assume you mean an air powered UGF?
My logic is based on a external filter powering an UGF & feeding the C02 in line, so you would get a very even distribution of the C02 rising up from the bottom?


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## roadmaster (14 Nov 2013)

Don't believe you could get a very even distribution up through the substrate for water which would be carrying the CO2,,? will alway's take the path of least resistance.
Some area's may get more than other's depending on substrate depth ,plant mass.
I once ran UG with reverse flow through small diameter grid of PVC with nearly pin hole size perforated pipe to prevent clogging.
Bottom grid resembled a hand laying on the bottom glass with finger's outstretched powered by Aquaclear power head's.
Water was then cleaned by a couple Aquaclear 110/'s.
Tank was set up for loaches ,pleco's,and worked well enough .
I can see using the return from canister to power the UG in reverse flow but think even distribution of CO2 would be difficult.


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## foxfish (14 Nov 2013)

I don't agree, I think that ten x flow coming up through a well designed filter plate & an open substrate like cat litter would offer vey good distribution, I have already experimented but not with anything long term.
I have a thread on this forum somewhere....
The tank might  still require additional flow, this is something I would have to experiment with but I don't think you would even need perfect even flow up through the UGF, especially if you had additional flow.
Most of the methods we use don't offer a very even distribution, a spray bar is good but you loose a lot of gas on the surface & it requires very good pressure to work well!
Distribution is one of the main issues we come across, have the C02 rising evenly from the bottom (if  it is possible) makes very good sense to me!


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## RichardJW (14 Nov 2013)

Seems to me that if the Co2 is coming through the substrate any dissipation would happen evenly across the bottom and not in the general water column . To get this to happen is obviously a task for the more technically minded amongst us - but it's a lot of work if it doesn't make any noticeable improvement . On the plus side it wouldn't need stripping down as it would stabilise the substrate whatever !! 


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## roadmaster (14 Nov 2013)

foxfish said:


> I don't agree, I think that ten x flow coming up through a well designed filter plate & an open substrate like cat litter would offer vey good distribution, I have already experimented but not with anything long term.
> I have a thread on this forum somewhere....
> The tank might still require additional flow, this is something I would have to experiment with but I don't think you would even need perfect even flow up through the UGF, especially if you had additional flow.
> Most of the methods we use don't offer a very even distribution, a spray bar is good but you loose a lot of gas on the surface & it requires very good pressure to work well!
> Distribution is one of the main issues we come across, have the C02 rising evenly from the bottom (if it is possible) makes very good sense to me!


 
 I was using three aquaclear 802's to power the UG in reverse flow in 75 gal tank and another approx 800GPH from two aquaclear 110's with fairly large gravel .
Cat litter and some of the specialty substrates would I fear, be too light with the flow proposed.


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## foxfish (14 Nov 2013)

Well I cant find the blessed thread but I have a few pics...


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## foxfish (14 Nov 2013)

Basically I laid a perforated PVC plate on top of the pipe with a few centre support & with the holes in the pipe facing inward the upward flow seemed to work very well!
So the water was taken from the surface overflow (on the right) & sent back into the pipes under the gravel via a needle wheel pump fed with the C02.


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## Tim Harrison (14 Nov 2013)

I used interlocking plates and mesh with soil/moss peat. It effectively gave me two oxidised microzones and roots penetrated the void below (which did not clog) and grew sorta hydroponically.


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## RichardJW (14 Nov 2013)

Think I certainly opened a can of worms with this topic ! Excellent feedback - more questions now than there is answers !


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