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Under-Gravel filter (UGF) mod


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Fun discussion on Opinions on Under Gravel Filters started by @Goosedub. Funnily enough, I just finished a UGF modification that I hope will help avoid channeling, clogging, and trapped fry  issues. This build provides some mechanical filtration, boosts filtration media surface area, reduces weight of the substrate (because foam weighs so much less than gravel), and lets me use coarse substrate (pea gravel).

Disclaimer: I installed this in a small, 10-gal, vertical (tall), hemispherical tank, which helps alleviate the problem of diminishing flow:distance ratio that would be more problematic in a larger volume, horizontal (low and wide, aka breeder) tank.

Note: I purchased the Penn-Plax Premium UGF for 40-55 Gallons ($17.99), which comes with four plates and four uplift tubes. That's enough to outfit two of my 10-gal tanks.

Okey dokey, here is what I did. 😎


1846049626_undergravel-filter-setup_1700x2400px_12FEB21_step1.jpg.14ed0a3fe6805c52c649f7c6812720ff.jpg573985627_undergravel-filter-setup_1700x2400px_12FEB21_step2.jpg.6d0b738397c1b639aaba9615aee5cb16.jpgStep 1: Trim coarse foam to fit the bottom of the tank, leaving a 1/2" margin. 











1724285104_undergravel-filter-setup_1700x2400px_12FEB21_step3.jpg.55e925eb381df5c0bcc83c5c6f1e5286.jpgStep 2: Trim UGF plate to fit bottom of the tank, again leaving 1/2" margin. The Penn-Plax plate is relatively soft plastic, so I used sharp scissors. 











1723826613_undergravel-filter-setup_1700x2400px_12FEB21_step4.jpg.bc849f54e437751a62296cf012acb061.jpgStep 3: Install uplift tubes, no-clog air stones, and vinyl tubing. I like the Penn-Plax UGF because the uplift tubes twist and lock into the plate. This helps keep me from accidently dislodging them when I gravel vacuum, embed root tabs, or move plants around. 









undergravel-filter-setup_2739x3600px_12FEB21_final.jpg.a162cc1a7cc4e2cc86a64c6a1bb4baa0.jpgStep 4: Cover with approx. 1 inch of gravel. Trimming the foam and UGF plate with a 1/2" margin lets me hide them behind the gravel. Add water, plants. Hook up air pump. Voila!

With such a small tank, I decided against using a powerhead. The photo was taken after running air for about 24 hours. The water cleared up over the next couple of days. The blue line marks the level of the UGF filter plate.











20210224_204112_final_24FEB21.jpg.c9959fe1f245a5d6b4ef4de292f42469.jpgHere is what the tank looks like today, roughly 2 weeks later. 














So far, so good! 🤓

Edited by Anita
a little clean-up
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Just now, Goosedub said:

Interesting Mod. Are you anticipating any trapping of detritus in the sponge media? There is going to be next to no cleaning of that media so I wonder if it will eventually get clogged up, like a sponge filter or filter media in another type of filter. 

Yes, there will be some buildup; however, that is the reason for using coarse foam media. The Aquarium Co-Op foam has very large holes, so it is less likely to clog. With only 1 inch of gravel, I should also be able to vacuum stuff up. You do want some biofilm/mulm in the foam media, providing biological activity for the nitrogen cycle. 

Hopefully, I will not have to dismantle the thing. Ugh! 😝


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51 minutes ago, H.K.Luterman said:

...it never occurred to me that you could modify [UGF]. That's a really neat idea. I'm interested in seeing how well it works in the long term.

For better or worse, I am a tinkerer. Haha! I was inspired after watching the Aquarium Co-Op video on hot-rodding hang-on-back (HOB) filters, Aquarium Filter Tips and Tricks! Start Saving Money Now! 

The good news is that if it fails, I only have to empty a 10-gal tank! 😈

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15 minutes ago, AquaAggie said:

@Anita what keeps the root tab contents from just getting pulled down into the sponge beyond the ready reach of your roots?  Am I missing something?

Haha, nope, you aren't. 😉Yes, it is certainly possible for root feeders to struggle in an UGF setup. From what I researched, this is more problematic with strong currents created by a powerhead. I am using air stones, which create a gentle flow. FWIW, several people in this recent post, Opinions on Under Gravel Filters, described growing healthy, thickly rooted plants with their UGF setups. 🌴

The only rooted plants I have in this tank are Vallisneria, which are not particularly heavy root feeders. The rest of the plants in the tank can absorb nutrients from the water. Flow velocity drops dramatically as you move further away from the source of the suction (flow:distance ratio). Ideally, I should plant the Vals near the front and as far away from the uptake tubes as possible, but I wanted tall plants in the back, so there you go. 🙃

I expect all the plants, the Vals included, will dine fairly well on fish/snail waste and other aquatic compost. I will embed root tabs on occasion, as well as use Easy Green, to ensure everyone is getting a balanced diet. 🍽️

The more likely problem I foresee, is the Vals' roots will "chase"  nutrients down past the gravel and infiltrate the foam until they block the water flow. Like tree roots in your sewer main line. 😬

At any rate, for me this is a way of gardening indoors. And as any gardener has learned, there are no black-and-white, hard-and-fast rules to raising plants. Or any living things, for that matter. If the Vals don't grow, I can just transplant them into one of my other tanks. 🌿

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