Undergravel filter

[western44]

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.

 

[_Maq_]

is very indicative of low oxygen.

But that's the point. We do need suboxic and anoxic zones in the substrate.

 

[Tim Harrison]

I can't imagine the flow would be evenly distributed throughout the entire substrate. I think it will inevitably exploit channels of least resistance. Therefore, it's likely there will still be zones with different radox potential across the whole substrate. But it really depends on how porous the substrate is in terms of grain size and interstitial space, and how homogeneous it is.

I used UG filter plates with soil substrate and a gravel tidy to prevent clogging. I also used gravel around the edges for cosmetic reasons. I'm guessing most of the flow occurred through the gravel, for instance. But the real advantage of UG filtration is that the flow beneath the plates creates an another oxidised microzone in addition to the one at the surface.

The oxidized microzone is the very thin highly aerobic surface layer of soil that interfaces with the water column. It is of huge importance in a soil substrate tank since it supports the hive of microbial activity needed to neutralise toxic substances and unlock nutrients.

Even though the system was low-energy, the plants thrived and many extended their roots in to the void below the filter plates, where they probably absorbed nutrients hydroponically as well.

 

[Andy Pierce]

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.

True this! Even for the under-substrate filter in the biOrb setup, they say to change the sponge part of the UGF every 4-6 weeks at £13 per go. Last time I did that was at least two years ago and next intended switch out for me is never...

 

[foxfish]

Great subject and not a new discussion as I can remember how popular UG filters were back in the 80-90s.
UG filters were always a favourite subjects in the glossy magazines, before internet forums but still heavily discussed in their day!
Fundamentally a great idea, a really large filter mass that also looks great……. sounds ideal.

 

[dw1305]

Hi all,

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'm pretty sure that isn't right. I've visited a lot of sewage works and they have terrific churn during the <"Activated Sludge"> process. Dissolved oxygen is the parameter that matters in nitrification, and everything else is really just froth.

The way I would look at it is that ammonia (NH3) is a scarce and patchy resource in the natural environment <"Microbiology: A fight for scraps of ammonia - PubMed">, so a microbe that has "grabbed" it, isn't going to let it go.

These papers look at nitrification kinetics, but you have quite a lot of variables
<"Research progress and prospects of complete ammonia oxidizing bacteria in wastewater treatment - Frontiers of Environmental Science & Engineering">, <"Nitrification and beyond: metabolic versatility of ammonia oxidising archaea - The ISME Journal"> & <"Ammonia-oxidizing archaea possess a wide range of cellular ammonia affinities - The ISME Journal">

cheers Darrel

 

[_Maq_]

The oxidized microzone is the very thin highly aerobic surface layer of soil that interfaces with the water column. It is of huge importance in a soil substrate tank since it supports the hive of microbial activity needed to neutralise toxic substances and unlock nutrients.

I've visited a lot of sewage works and they have terrific churn during the <"Activated Sludge"> process. Dissolved oxygen is the parameter that matters in nitrification, and everything else is really just froth.

I'm very grateful to you for spreading these pieces of wisdom among amateur hobbyists.
I've been struggling to persuade my compatriots-hobbyists of these facts. Most of them still believe that good substrate = well-oxygenated substrate, and that what bacteria need most is colonization area.
From these misleading positions, much of aquarium business evolves. Vendors sell substrates which "enable good penetration of oxygen", "feature porous surfaces to accommodate lots of beneficial bacteria", and so on. Also, the huge filtration business is based on these and similar false assumptions.

 

[Oldguy]

We do need suboxic and anoxic zones in the substrate.

It must be a given that with a UG system there will be differences in flow rate and dead spots across the aquarium substrate. Therefore there will be anoxic zones BUT I would prefer that these were very small, the largest home aquarium is very small compared with a modest natural pond and an oxygen rich environment is in my opinion the safest bet for home aquariums.

 

[Aqua sobriquet]

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.

View attachment 208671

I did the same thing on a freshwater tank. It worked well enough but I did have an issue when I had a blockage somewhere. I can’t remember exactly what happened but luckily the floor didn’t get wet.

 

[_Maq_]

It must be a given that with a UG system there will be differences in flow rate and dead spots across the aquarium substrate. Therefore there will be anoxic zones

True. Still, I have my doubts about forced mass flow in the substrate. It's not a standard situation.
For the same reason I'm reserved about under-gravel heating cables.

an oxygen rich environment is in my opinion the safest bet for home aquariums.

Again, I agree. But I believe the key is oxygen rich water column. That's the prerequisite that plants can pump enough oxygen into their roots, and that oxygen-depleted zone does not reach the uppermost layer of the substrate. Everything below that layer should remain suboxic / anoxic. The richest and most important microbial processes take place at the oxic-suboxic interface, and these spots should not be too far from plants' roots. If the substrate remains oxidized, acquisition of some nutrients, esp. phosphorus and transition metals, is compromised.

 

[foxfish]

It would be quite possible and easy enough to adapt the principle operation by lifting the undergavel bed up from the tank floor.
I have done this in several home tanks ( i might even have a thread somewhere) by placing a matrix of pipe under a perforated plate. This means you can obtain a more even flow up through the gravel bed and an opportunity to back flow the gravel bed during water changes.
I have used this format in many large koi ponds, some have been running with this style of planted gravel filter for over 30 years and still going strong!

 

[Oldguy]

acquisition of some nutrients, esp. phosphorus and transition metals, is compromised.

This may well be so for natural waters.
However people, myself included, grow many plants attached to wood* etc where their roots are not in the substrate but hang in the water column as is the case with floating plants. Redox at the water root/root hair interface is any ones guess, but grow they do.
Many submerged plants have a large leaf area to take in minerals dissolved in the water column, while high in CO2 is also high in O2, with fish behaving normally . Any difficulty with iron and other transition metals can be overcome by the addition of their chelated salts. As for phosphates I think EI has it covered.

*Removed all wood and now attach plants to ballasted 3/4" plastic pipes. Pipes blinded by lots of plants.

 

[Gill]

UGF are so underrated, I have grown many a heavily planted tanks using UGF in standard tank and BiOrbs.

 

[dw1305]

Hi all,

It must be a given that with a UG system there will be differences in flow rate and dead spots across the aquarium substrate. Therefore there will be anoxic zones BUT I would prefer that these were very small, the largest home aquarium is very small compared with a modest natural pond and an oxygen rich environment is in my opinion the safest bet for home aquariums.

I think what you want is just a patchy environment, a mosaic of <"fluctuating REDOX levels"> in the rhizosphere and substrate. I'm not convinced that it really matter how you get there.

cheers Darrel

 

[_Maq_]

Some of you maintain that undergravel filters work well. What I'm still missing is an answer to the question what do they do? Do they help keeping the water clear? Do they help preventing algae? Do they support microbial processes? Do they enhance plant growth?
In short, do they do any good?

 

[Oldguy]

what do they do?

Massive pre-filter for the canister that drives the uplift and as such will remove suspended particles from the water column without clogging the filter material in the canister. (A lot of people just attache a power head). Can be part of the general water movement of the tank. Keeps the substrate 'warm' I have had very low tech tanks with a noticeable temperature gradient in the water column and a cold substrate. Home to micro-organisms and a mix of Redox areas which may or may not be beneficial for plant growth.
I assume that any benefit for plant growth is a bonus because I add ferts to the water column. Currently have an Amazon Sword (supposedly a heavy root feeder) growing in my system that is now growing out of a 20" water column to support emergent leaves. I do not know if these leaves will tolerate lowish humidity or dry out, even LED lights give out heat. I will just have to wait and see. I hope that the leaves not only survive but thrive, access to atmospheric CO2 could produce even stronger growth.

 

[Andy Pierce]

... and what they don't do is suck up baby shrimp!

 

[Jorge O'Reilly]

Hey, I didn't want to make a new thread for one random question so I'll just stick it here. If one were to make an UG filter or something similar (not exactly), would the water movement in the plant roots be detrimental to their growth?

I'll expand. I've been looking into making a new setup with my old 25-liter tank, and wabi-kusa has me really tempted. So what I thought of was getting a glass cylinder, sticking it in the aquarium, placing a wabi kusa ball in the middle of it and using the rest of it as a sort of UG filter/weird internal canister thing. I'm not sure whether this is clear enough so I'll see if I can whip up some sort of schematic for it.

So the proportions are way off, but this way it's easier to see. Would the water flow affect whatever plants I might want placed there?

Cleaning would just be a matter of removing the WK ball, wmptying out the gravel and giving it a small rinse, half at a time.

 

[Tim Harrison]

I doubt it, plants grow well hydroponically. I know it was the usual excuse back in the day when folks plants didn't grow or melted. I guess an UG filter was a common element and so it, or rather water movement around the roots, got the blame.

Dr Timothy Hovanec's comments about Bacterial supplements

All-important for what? The plants, or the nitrifying bacteria? Hi @lilirose As carbon is a fundamental element required by all living things, it applies to both of the above. But, I was specifically referring to the nitrifying bacteria. JPC

www.ukaps.org

 

[zozo]

Hey, I didn't want to make a new thread for one random question so I'll just stick it here. If one were to make an UG filter or something similar (not exactly), would the water movement in the plant roots be detrimental to their growth?

I'll expand. I've been looking into making a new setup with my old 25-liter tank, and wabi-kusa has me really tempted. So what I thought of was getting a glass cylinder, sticking it in the aquarium, placing a wabi kusa ball in the middle of it and using the rest of it as a sort of UG filter/weird internal canister thing. I'm not sure whether this is clear enough so I'll see if I can whip up some sort of schematic for it.
View attachment 208913


So the proportions are way off, but this way it's easier to see. Would the water flow affect whatever plants I might want placed there?

Cleaning would just be a matter of removing the WK ball, wmptying out the gravel and giving it a small rinse, half at a time.

Your idea is already very effectively proven in the Organic Pool/Pond building but then realised with a UG filter driven by an Airlift pump. Airlift has the advantage of no submerged mechanical parts and therefore relatively maintenance-free, it can't really clog. But it requires a different construction method. But the rest is the same, flow is flow doesn't matter what makes it.

Anyway, a picture says more than 1000 words... It concerns a partially separated via surface water-connected basin filled with a substrate/Gravel. In the substrate is a perforated Drainage pipe connected to the airlift pump in the pond. When the pump is active the rising air bubbles create a flow of aerated water drawn from the planted substrate basin. Thus the water cycles from the pond into the planted substrate and back to the pond.
People who use this concept only report phenomenal results in plant growth and water clarity... Next to this, it's extremely cost-effective.

https://www.youtube.com/@organicpools-davidpaganbutler/videos

Has a dedicated YouTube Channel about it...

If I'm ever to build a pond again I'm 100% in without a shred of doubt... This is the way...

Looking at your diagram, the airlift pump could be placed into the Wabu Kusa cylinder with the outflow of the pump over its top back to the tank.

I changed your diagram with my idea at the other side... Then the WB cylinder should be completely submerged, maybe ½ inch below the water line is enough. Water will draw back into the cylinder from above and the airlift pump draws it back out again to the tank.

This could work, tho have yet no clue nor experience how this works for a long period in smaller volumes and surface areas. That would be the trial and error part.

 

[Polly]

Some of you maintain that undergravel filters work well. What I'm still missing is an answer to the question what do they do? Do they help keeping the water clear? Do they help preventing algae? Do they support microbial processes? Do they enhance plant growth?
In short, do they do any good?

Back in the early 80s I set up an undergravel filtered aquarium run with an air pump.
Fully planted. The plants thrived. Various Fish species were thrived and bred. We had regular babies grow out in the tank with no help from me . Water - crystal clear.

Didn't feed the plants, didnt think of it, no products in our little local shop, or in the one in the city. Never saw any algae, my Whiptail cat took care of that. The Cory's barbels were magnificent. Pearl Gouramis looked fabulous as did the Danios.

Maintenance was low, regular monthly waterchanges with a gentle gravel vacuum at the same time.
To create a more even flow, the substrate (small pea gravel - it was all we could get) was built up around the uplift tubes (×2) and gradually decreased as it got further away.

So yes. They work. And plants will grow - at least with gentle flow from an air pump.

Tried in early 2000s with a powerhead on the uplift tube, but plants didn't like it. And I got used to the silent running so ditched the UG filter. If only there was a truly silent air pump !