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Undergravel filter

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western44

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Hi all, i was in a lfs not my usual lfs and i noticed they had undergravel filters for sale, something that i have'nt seen for many years.
It got me wondering as i have a spare tank, would it be possible to run an undergravel filter with a small external filter, if so how would
you do it. Thanks in advance.
 
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Yes you can run an external on an UGF. Have done it in the past. Just used a pond fitting to reduce to the size of the external pipework. Or you can run them using powerheads with the tapered inlet.
With an external it turns the whole UGF into a massive prefilter. And then you can gravel vac it every so often.
 
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Back in the day, I ran UG filters with a canister filter on a marine tank, but had it running in reverse so the water came up through the sand and the canister filtered the coarse detritus. But either way will work well, especially with plates and relatively coarse substrate like pea gravel.

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And there are so many styles of UGF plates. The standard ones in the uk by Algarde style are crap. The ones Tim posted are a much better plate as more surface area.
The Japanese ones that sit in spindles let you put bio balls under the plate etc. They are mainly used in shrimp tanks etc.
 
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western44 said:
undergravel filter
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Tim Harrison said:
coarse substrate like pea gravel.
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I run a UG in my planted tank. I used garden weed suppression fabric on top of the plates and then ordinary 'fine' gravel substrate on top. The weed suppression fabric is surprisingly porous and water just flows through it.
foxfish said:
good way to distribute C02.
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Interesting point. My CO2 is injected via two diffusers linked to a common spray bar at the top of the tank, but some of the CO2 rich water which hits the front of the tank and flows back across the substrate to a bank of inlet strainers just of the substrate floor must get sucked down into the substrate and returned via the canister filter.
The canister filter is not part of the CO2 diffusion system which is driven by two power heads and inline but in tank diffusers giving a left and right bank inputs but a common out output.
 
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Oldguy said:
I used garden weed suppression fabric on top of the plates and then ordinary 'fine' gravel substrate on top. The weed suppression fabric is surprisingly porous and water just flows through it.
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Hi,
Does it get clogged after a while? I was thinking of doing the same in mine tanks, but then I decided to go with the plates with larger holes and coarser gravel options.
 
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I often consider this option of a reversed flow undergravel filter for my imaginary future tanks, but I worry about not having an anoxic region in the substrate. How would it impact micro elements availability to plants? How would it impact root function?

I particularly like the idea of inserting CO2 rich water that uniformly sprouts everywhere.
 
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Andy Pierce said:
In my biOrb based set-up which has "under-substrate" filtration driven by an air pump based water lift, the "coarser gravel" is biOrb "ceramic media" and I just dump Tropica aquasoil (2-3 mm size) on top of that and seems all good.
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Does it not wash all the soil nutrients out into the water column? I like the idea of putting some filter media below the soil.

Oldguy said:
No its been running for over 15yrs, but you do need to vac the gravel from time to time. I try for once ever other water change when stem plants are thinned out.
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I guess I will have to try it with my next setup.
 
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Reverse flow UG filtration sounds very doable, especially with substrates like Amazonia and Tropic AS.
Maybe it could be the next new planted tank innovation, as @foxfish mentions above.
Maybe we just need someone brave enough to try it and lead the way.

hax47 said:
Hi,
Does it get clogged after a while? I was thinking of doing the same in mine tanks, but then I decided to go with the plates with larger holes and coarser gravel options.
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Gill said:
You could also use crotchet netting
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Or perhaps Gardman greenhouse shading mesh. It's what I've used for ages to separate soil and capping substrate.
Back in the day you could buy similar material to put over an UG. It was known then as a gravel tidy.
 
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Over the years I have found under gravel filters to be the best low maintenance filters.
There are 2 tipping points. Both are relative to stocking density and feeding
Me - High density stocking, high feeding.

1. if run slowly using an air lift they are good for 6 - 12 months then they throw out ??? bacteria, or fast growing string algae around the outlet. and any plants near
2 you need to give the gravel a major wash every few months, it depends on your balance
(Tried Fluvals - 304/5 need doing every 3 weeks)

The slower you go the larger the area it "sucks " from, the higher power , power heads tends to concentrate the suction around the base of the uplift pipe. diminishing the effectiveness.
I read somewhere it takes bacteria around 20 mins to convert ammonia to nitrate, think it was a Matten filter place, / group, anyway flow speed is important
I used purple dye (Potassium permanganate) in a 2ft tank to figure this out a few years back. I came to the conclusion, undergravel filters are great until they become overloaded, after that you need sponges, to get rid of the "dusty" outflow.
It's simply a balance too many fish to much food and bateria go rampant as well as algea, I see algea as natures way of telling me something is out of balance. Further along, green water is ok, brown not so good, white is bactirial watch it 24H should clear , if grey change it quickly.

Simply if your tank runs well with a foam /sponge filter an undergravel filter will mean you need less maintenance.
Me I over feed, I overstock, I have started a constant flow system, new water in, old water out.

It all depends on what your doing or your ideas, me breeding goldfish, a 8" x 10" x 16 tank is ok while they are babies I have lots of flow. I run undergavel filers after them a big plant tank, I like them, I also have constant flow of new water as well.. its all down to "the " balance.

Water Flow = Oxygenation
O2 = life
 
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LMuhlen said:
I worry about not having an anoxic region in the substrate. How would it impact micro elements availability to plants? How would it impact root function?
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In my country hobbyists' community, strongly negative opinion on undergravel filters prevails. The reasoning goes that it's "unnatural", impacting negatively redox, microbial community, nutrient availability, root function, etc. I tend to believe the same; still, I'm curious what the actual result would be. I've never tried.
 
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I am very distrustful of stagnant substrates, they may be natural but when wading through them the pong that comes up is very indicative of low oxygen. Now there will be gas exchange if there are lots of 'reeds' and water lilies with floating leaves but these conditions are not typical of our home aquariums.
I think the real reason that UGs are not popular is the low profit margin on these items. They are fit and forget one offs. Fancy power filters with disposable filter pads/cartridges are a money spinner and keep the punter coming back into the shop.
The gravel does need to be 'vacced' ( I use term not in the Street Meaning) but not every part and not all of the time. Used as a massive pre-filter to a canister filter, the later need very little maintenance, especially if filled with a high flow medium.
 
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jaisol said:
The slower you go the larger the area it "sucks " from, the higher power , power heads tends to concentrate the suction around the base of the uplift pipe. diminishing the effectiveness.
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I don't think there will be evenly distributed flow across the entire gravel surface. The farther we go from the uplift tube, the smaller the driving force will be for the flow, since the pressure difference will be smaller through the gravel depth. So it's natural to have the biggest suction near the tube. But unless the flow resistance goes infinite at some point, there will always be some flow everywhere. The absolute flow rate differences will be bigger with a pump though.
 
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