Beating the $#@^ out of an old friend...

Okay, admit it...the title got you.

It's not what you think...Well, maybe.

As a fish geek, I spend a lot of time just...musing about stuff. Thinking about ideas and techniques that can help create a better and more enjoyable hobby experience. And often, I think about things like husbandry of our botanical-style, blackwater aquariums. 

Having been in this hobby literally since I could walk, I've been fortunate to see a lot of incredible developments, both from a technique and technology perspective. I think a lot about some of the equipment that I used over the years while growing up in the hobby...Particularly filters. I have no idea what I'm fascinated with filtration...except for the fact that I like to see as little of a filter in my tank as possible, if at all.  I've tried a ton of filters over the years...There sure have been some interesting ones...some which came and went; others which have stuck with us...

You know, those old hang-on-the-back air-driven outside filters, sponge filters, and the most venerable of 'em all- the under gravel filter! I never really quite understood this one, to be quite honest with you. Yet, it makes me think about some positive takeaways...

The under gravel filter.

Once considered stay-of-the-art, almost "essential" gear for any hobbyist, this one has fallen by the wayside for many reasons. And I think it "suffered" from it's own "efficiency" at doing what it did best- pulling stuff into the substrate. 


Okay, let's do the most cursory intro to the UGF and how it works.

The "filter" is essentially a plastic plate that goes under the "gravel" (hence the name), and is designed to pull water down through the substrate that sits on top of it via use of air stones or (back in the day) a powerhead...Oh, wait- did I say "the gravel?" Yeah...well... Okay. You need materials which is coarse enough to function as a sort of "screen" for particulate, otherwise this stuff could slow down the flow considerably, creating all sorts of issues, ranging from just being plain old dirty" to acting as a "nitrate sink."

However, it’s part of a cycle of sorts, right?

I mean, it's pulling dirt and organic material into the substrate. Is that a good thing, or? Well, if you get "dead spots" under the plate (Who the #$%^ knows if that was a "thing" or not. There is likely some physics behind that! Sounds scary, regardless), which could lead to anoxic areas and perhaps buildup of hydrogen sulfide or other nasty stuff which is  "no bueno"  for aquariums, right?

And you have to clean the substrate so that it doesn't "clog" with detritus, supposedly... And if you overdo it, you essentially wipe out billions of beneficial bacteria that you're actually trying to

Anyways, the principle here is that the substrate acts as a biological filtration "base." Now, this actually seems problematic from the get-go, right? I mean, you're using a coarse substrate to trap shit (literally) in it, where bacteria break it down. And of course, this necessitated the use of some form of supplemental filter, like a canister or outside power filter...

And that always made me wonder why you'd even f--k with a UGF in the first place if the whole idea was A)For the substrate to act like a biological filter and B) The fact that you need a supplemental mechanical filter to remove the particulate waste that the UGF would accumulate through its ability to pull stuff into the substrate.  

Like, just have a substrate layer and an airstone in your tank and call it a day, right?

I mean, sand beds have their own unique ability to foster denitrification and other biological processes, and do you even need a filter plate to accomplish this? Okay, read up on "plenums" form the early 21st century in reef keeping for more on that, but...I mean, just facilitating a healthy sand bed or substrate layer- meaning, one that isn't absolutely loaded with fish poop an uneaten food- is half the battle, right?

Notice I didn't even bring up our friend, "detritus" at all? Because, as you know, I have warm feelings about the stuff. And of course, there is something all very weird about the idea of using a mechanical device to further pull waste material into the substrate.

Now, in a botanical-style aquarium, with a layer of leaves and botanicals, many of which are decomposing from the minute you add them to the tank, what advantage would having a mechanical device physically yanking this stuff deeper into the substrate accomplish?

I mean, I'm a huge fan of using substrates to create not only an aesthetic component to our aquariums, but to function as a biological "filter" of its own. I mean, the substrate is alive. It's actually the largest organism (or more correctly, aggregation of organisms; ie; bacteria) in any given aquarium, when you think about it, right?

Okay, I"m really all over the place with this stuff today...For some reason, I felt compelled to do a bad analysis of the UGF, while simultaneously recalling its nostalgic charms and then beating the living shit out of the idea! All the while, demonstrating my appalling lack of scientific understanding of the whole concept, right?

Yeah, this blog is really productive! 😆

Yet...I have a fascination with the biggest part of the idea of the UGF: It essentially "runs" by facilitating the growth and reproduction of beneficial bacteria

I have a tougher time reconciling the whole idea that your "gravel" becomes a mechanical filter. It seems sort of unnecessary, because it more or less functions like that anyways, right? I mean, without a plastic air-driven filter plate and lots of maintenance concerns. 

Isn't this like the whole "balanced aquarium" stuff that's been bandied about the hobby for generations?

I love things that work with Nature and her natural processes. I love the fact that we play with leaves that break down, fueling bacterial growth, which also serve to facilitate denitrification in our tanks. And the fact that the decomposing botanicals and such are essentially "food" for many of the organisms which reside in our tanks.

Indeed, they facilitate the creation of a sort of "food web", don't they?

I think so.  

So, there’s this “thing” I have about substrates in general, because they form one of the most interesting and useful components of the closed aquarium ecosystem. And it’s a bit ironic- or perhaps, just coincidental- that the undergravel filter, which holds some strange fascination for me, utilizes the substrate as it’s “media...” 

I mean, I suppose there's more to it than that; it's worthy of more attention...Not necessarily the idea of bringing back the under gravel filter, mind you- but the idea of substrate as a biological filtration component.

There is so much more to discuss here.. so much more to think about.

So, time for me to stop beating up this old friend, the UGF, and think about the substrate itself some more..

Until next time...

Reflect on the past  while thinking about the future.. 

Stay curious. Stay thoughtful. Stay diligent. Stay creative...

And stay wet.


Scott Fellman

Tannin Aquatics


Scott Fellman
Scott Fellman


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