What Do You Think Of Undergravel Filters?

HI everyone! My new low tech tank idea involves a pump pushing water into a hydroponic clay media layer below the dirt and sand layers, thus more thoroughly oxygenating the substrate and preventing it from becoming anaerobic like my prior experimental tank. However...it occurred to me that this would effectively be a reinvented undergravel filter I'm not sure how relevant this question is, but what are some pros and cons to such an undergravel filter, especially considering that I cannot easily clean this version? Thanks

 

I think the poor old UGF has gotten a very bad rap, largely due to ignorance of how it works. Assuming you have a couple inches of reasonably sized substrate on top, it clearly presents a massive surface area that would be difficult to duplicate in a typical HOB or canister filter. For the same reason the Hamburg Matten Filter (HMF) is usually so effective, a properly set up UGF should provide excellent reduction of ammonia and nitrite, possibly even some nitrates if the substrate is deep enough and flow not overly fast.

The only downside is accumulation of detritus. This shouldn't be a huge issue if you're not overfeeding. I think it's also somewhat misunderstood. We see brownish gunk when the substrate is vacuumed and think it's clogged and polluted when, in fact, this is an all-you-can-eat buffet for the beneficial bacteria. It's clearly a problem if it's clogging the substrate, but short of that, assuming your water parameters are good, it's primarily a cosmetic issue that would be out of sight if we weren't messing about. Nature isn't always pretty. If the fish keeper can get past the idea that there's brown gunk in their gravel, the UGF can provide very good filtration.

You didn't say what volume of water the pump would be moving. I wouldn't try to push too much water through the UGF.

I also think the layers you have in the substrate are going to present issues when cleaning. They're going to eventually mix, especially since the bottom layer has the larger grain size. Any disturbance of the substrate is going to speed up the mixing. So if you vacuum the bottom you're going to need to be very careful to disturb it as little as possible.

 

HMMM...I may want to give this more thought then. Thanks

 

Joshaeus , in regards to using a pump..... is the idea to have the pump use the UGF's uplift tube as an intake and drawing water from it, to drastically increase the flow through the UGF?

Or is the pump going to be used for a reverse-UGF style setup, where water is pumped into the uplift tube and into the UGF, where it then rises upward through the substrate?

 

The pump will push water into the clay hydroponics media, and the water will then rise back up through the substrate.

I think the poor old UGF has gotten a very bad rap, largely due to ignorance of how it works. Assuming you have a couple inches of reasonably sized substrate on top, it clearly presents a massive surface area that would be difficult to duplicate in a typical HOB or canister filter. For the same reason the Hamburg Matten Filter (HMF) is usually so effective, a properly set up UGF should provide excellent reduction of ammonia and nitrite, possibly even some nitrates if the substrate is deep enough and flow not overly fast.

The only downside is accumulation of detritus. This shouldn't be a huge issue if you're not overfeeding. I think it's also somewhat misunderstood. We see brownish gunk when the substrate is vacuumed and think it's clogged and polluted when, in fact, this is an all-you-can-eat buffet for the beneficial bacteria. It's clearly a problem if it's clogging the substrate, but short of that, assuming your water parameters are good, it's primarily a cosmetic issue that would be out of sight if we weren't messing about. Nature isn't always pretty. If the fish keeper can get past the idea that there's brown gunk in their gravel, the UGF can provide very good filtration.

You didn't say what volume of water the pump would be moving. I wouldn't try to push too much water through the UGF.

I also think the layers you have in the substrate are going to present issues when cleaning. They're going to eventually mix, especially since the bottom layer has the larger grain size. Any disturbance of the substrate is going to speed up the mixing. So if you vacuum the bottom you're going to need to be very careful to disturb it as little as possible.

For whatever reason I did not ask this question on a previous post...would a thin layer of gravel above the hydroponics media and below the sand and dirt reduce the amount of clogging to a useful degree?

 

Back in the day - we started out with an undergravel filter. They were horrible... Worst. Thing. Ever.

Addition of a then bleeding edge technology HOB filter revolutionized tank care and solved most of the problems we had with clogged under gravel filtration. And allowed us to unclog/rinse out the media and dump the filter sump without causing a giant catastrophe in the tank.

The trouble with Filtration in the substrate is that "fixing it" requires tearing all the substrate back out which causes 50x as much trouble as any benefit it might have provided.... Plant roots clog it.... Too much algae clogs it.... Too much organic matter clogs it.... Silt clogs it. Age clogs it.... etc.

 

For whatever reason I did not ask this question on a previous post...would a thin layer of gravel above the hydroponics media and below the sand and dirt reduce the amount of clogging to a useful degree?

Any time you layer materials of different grain size there is going to be mixing of the materials. This is particularly an issue with something like beach sand where the grains are smooth.

Many years ago somebody filled a small glass bottle with layers of different colored sand and gave it to my father. It has sat on a shelf above his desk ever since. Over the years, just from vibration of people walking in the room and opening drawers in the desk, the layers of sand have merged to an obvious degree. You can still see where there were layers at one time, but the clean lines are long gone and the colors blended quite a bit. And this in a situation with grains of the same size and an effort made not to disturb the bottle.

Since the hydroponic clay is there strictly as a filter media, you could put landscape fabric on top of it. That would keep the soil and sand from mixing down to that level, but it might also create a point where gunk could accumulate and clog the substrate.

I don't think you're going to have a huge issue with clogging. The fine grain of the sand will keep a lot of the larger gunk from getting down in there. If you surface vacuum regularly you should be able to keep clogging from being an issue. The reverse flow should also help.

I would suggest putting a foam pre-filter on the pump intake. That should keep a lot of the muck from ending up under the UGF plate.

 

I think there great I'm still running one on my 60 gallon(along with a canister fliter). When I got my tank it was included with it .A lot of people think there outdated and the old days of fishkeeping and not many people use them anymore,but I know quite a few that still do.it has it pros and cons but the but I think the pros outweigh the cons imo ,a UGF can bring lots of oxygen to a tank..the power heads on the top of the tubes will create a current in the tank so the water will never really be to stagnant ,the plate on the bottom will protect the bottom glass and create somewhat of a cushion and also hold a lot of beneficial bacteria ,some also say that it can help plants grow even better due to the oxygen being supplied to the roots.some people also think it it would trap a lot of gunk under the plate, but as long as you do your weekly water changes siphoning , it shouldn't be a problem. I had a UGF running on a tank for over 20 years and when I had to tear it down to get a new tank I was quite surprised as to how little gunk was under the plates

 

I think one of the bigger issues with the UGFs of old was the lack of availability of good quality air stones. Almost all of them would clog rather quickly and you'd end up either constantly changing out air stones or living with one little stream of bubbles rising in the tube. A power head fixes that, though in some cases it may fix it too well, moving water through the substrate almost too fast. I know I put a couple on the UGF in my 55 and they were pushing a LOT of water.

The Czech lift tube would be a perfect match for the UGF, though I've not seen anyone selling a kit that pairs the two. Pair a couple XL Jetlifters with UGF plates in a 100 gallon tank, supply enough air (500l/h/tube), and you can move up to 1000 GPH.