Under gravel filter idea

[Rblouch85]

Ok, so we all know what an undergravel filter is, and how it works, right? Right.

So I have had this crazy idea about my undergravel filter. I have a 75 gallon freshwater tank.
So what I was think was lining the bare bottom (thinking I need a thin piece of filter batting to keep the ceramic off the glass) of the tank with ceramic bio media. Something like the rectangular stuff you put in your canister filter or HOB filter. Then, directly on top of the bio media, place my UGF plate and cover with substrate. Then, I was also thinking of using a power head, instead of the air pump and stone, to circulate the water.
My line of thinking in doing this is to exponentially increase the available surface area for bacteria. What do y'all think?

 

[FreshyFresh]

I think what ever you put below the UGF plates will just get choked with solids over time. The substrate on top of the plates will be home to all the beneficial bacteria you need IMO.

 

[Wyomingite]

Ok, so we all know what an undergravel filter is, and how it works, right? Right.

So I have had this crazy idea about my undergravel filter. I have a 75 gallon freshwater tank.
So what I was think was lining the bare bottom (thinking I need a thin piece of filter batting to keep the ceramic off the glass) of the tank with ceramic bio media. Something like the rectangular stuff you put in your canister filter or HOB filter. Then, directly on top of the bio media, place my UGF plate and cover with substrate. Then, I was also thinking of using a power head, instead of the air pump and stone, to circulate the water.
My line of thinking in doing this is to exponentially increase the available surface area for bacteria. What do y'all think?

I see where you're coming from, but the need for additional biological filtration is unnecessary. If you keep the gravel free of debris and have decent flow across the full area of the plate, with the gravel at a depth of 2" or so, you should have all the biological filtration you need. These filters are designed to utilize the gravel for that purpose. The difficulty in maintaining decent biological filtration with undergravel filters comes from low or irregular flow, not from inadequate surface area for nitrifying bacteria. Problems usually arise from substrate clogged by poo and uneaten food being pulled into it, compacted gravel or uneven flow through the gravel, often due to weak flow from an old air stone or under-sized air pump.

If you want to increase the efficiency, set the filter up on a reverse flow system. Set the power heads up with a sponge on the inlet, and direct the flow down into the uplift tube. Instead of water being drawn into the gravel from the top, down through the gravel and out the uplift tube, it will be drawn out of the main water column, down the uplift tube, under the plate and up through the gravel. This will keep stronger flow through the gravel (your biomedia) and reduce plugging the gravel, as most mechanical filtration will occur with the sponges on the inlet of the air stones and not from material being pulled into the substrate. There are plenty of ways to set a reverse flow under gravel filter up for maximum efficiciency, I suggest a google search for RFUGFs and look at some of the set-ups.

Under gravel filters get a bad rap, but they can be very efficient if set up correctly and properly maintained. I don't use them mainly because cichlids dig too much and uncover the plate, or because they don't especially go well with live plants.

WYite

Edit: Now that I think about it, I think Rbishop uses RFUGFs in some of his tanks. Maybe I'm remembering something else I read.

 

[fishorama]

We had UGF for many years & I'm not unhappy we don't anymore, fish can end up under plates too...but I also wish I'd have tried reverse UGF in even 1 tank. Now I'm more into plants so no plates in either flow direction...roots clog the plates up ... It's a PITA to have clean under the plates & eventually you will with UGF...crap collects under there. But maybe not with RUGF...

Yeah, Bob, do you still do RUGF? I think you might...old dog, old tricks? What the maintenance like? Gravel vacuuming? or what? 2 filters?

 

[dougall]

Not a fan of undergravel filters in the first place, because of the interaction between them and plant roots,,, and the fact that I prefer plants.


Are you having problems not having enough surface area for your bacterial colony as it is?

 

[TwoTankAmin]

Floss type material clogs pretty much faster and more completely than any media you can use. maybe diatomacious earth might clogh faster and more completely.

My very first tank had a UGF and and Emperor 400. Yikes. The UGF was powered by a powerhead which sat atop one uplift tube. I had plastic and silk plants.

I then got more educated re UGF and switched it over to an RUGF. This ran using a reverse flow powerhead with a large sponge over the intake. I used to put a net over the sponge and then unplug the powerhead and lifted the entire thing out of the tank. I did this weekly to rinse the sponge. At this time among the fish in the tank were panda corys and common orange swordtails of both sexes.

Having read about gunk accumulating under the plate and having the tank on a metal stand, I could see up though the bottom glass and, using a flashlight, I was able to take a look for any gunk build-up issues. What I found were several panda and sword fry swimming around under the plate. Occasionally, when removing the powerhead, I would accidentally raise the uplift tube out of the plate slot (but not the gravel bed) and then work it back in when I returned the powerhead. The top of the uplift tube had to be well below the water surface in order to accommodate the powerhead intake sliding into it and the powerhead then being completely submerged. This created two ways for those babies to get under the plate.

It was during this time and had been explained that one of the benefits of having live plants was one could stock more heavily. the helped to filter and broke up lines of sight. So I made two decision. I would break down the tank and free the fry. Then I would put back the plate and gravel and put in live plants.

I am not sure if the posts I made here in a thread relative to plants and under gravels and had a bit of a disagreement with Tom Barr. Basically, I was questioning the wisdom of using gravel ferts. with an RUGF. I felt it would be pushing ferts out of the gravel and into the water column. I believe Tom was promoting the excellent concept of using both substrate and water columm ferts together. I think I had not yet begun using Jobe's Spikes in planted substrates. (I am still using them 18 years later.)

I never stayed with the UGF long enough to stay with it. I think I first disconnected it and ultimately, during a major redo removed the plate. So I never saw it overwhelmed by root mass. One thing I did do was put some plants in clay pots mostly buried in the substrate and also did some anubias and ferns.

A UGF or an RUGF using the proper size and depth of gravel is still one of the best aerobic bio-filter home for needed microorganism in tanks. it is massive and all of it gets good circulation. An RUGF with a secondary power filter for mechanical filtration is essential. It is also essential to pre-filter the intake for the intake tube. Air power wont work well at all.

That pre-filter must not be allowed to fill up and restrict flow. Because the flow is up through the gravel, it can take a very long time or never for gunk accumulate under the plate. It should mostly never reach there. And most things that try to settle into the substrate will be pushed back up into the water column by the reverse flow. There it can be captured by the added hang-on filter rigged for mechanical which can also act as a place to put carbon (or chemical media) should any be needed. It's return will also foster gas exchange at the surface and keep the water oxygenated.

As long as one sticks with plants in sealed pots, attached to wood, rocks etc. and floaters, you can have them. However, never forget your filter is your substrate. Too many things impeding the flow through the substrate will eventually reach the point of reducing the benefits of having it. Also, the optimal gravel for under-gravel use is not the ideal size for plants.

 

[fishorama]

I think, TTA, you are or were better at tank & plant mantenance than I am or was. I had both java fern & anubias roots work their way into the UGF plates eventually, or even just any substrate, plates or no. Not like sword plants clogged them up but still...if they can reach they will root anywhere. My bolbitus roots are not quite so vigorous but they do it a bit too...

 

[TwoTankAmin]

I never went long enough with my UGF/RUGF to see anubias roots become decent size in the substrate. Anubias prmarily use their roots for anchoring. They are not a true aquatic plant in that they do not to be submerged all the time. Many of the p;ants we use are like this. While they do fine submerged they are often only this way during rainy season. The rest of the time they grow above water but with their roots either submerged or in pretty wet soil.

Anubias are like this. They often grow alongside rivers and waterfalls. They stay wet but not submerged part of the time. This also means they can be grown emersed- most of the plant is above the water and they grow faster this way and do not have to deal with algae and snails. However, anubias will also be fine if submerged years round, they just grow more slowly this way.

I wll default again to the idea that if you want to have an undergravel set-up, grow the plants in pots. If you do anubais you can prune the roots going into the substrate as long as they have other roots or methods hilding them in place. Here is a somewhat recent picture of one of my 75 gal. tanks. It ended up as a place to park excess plants and fish. the picture is old because today miost of the pmanys are all the way to the surface/ Noy one of the plnts in the picture is planted in the sand substrate which is only about 1 inch deep. All plants are either in clay pots or attached to rock or wood.

I apologize for poor photo skills and an old camera.

 

[fishorama]

Anubias grow 2 kinds of roots, the anchoring type & finer feeder 1s. I saw this but didn't really understand the difference until OrionGirl (I think) pointed it out.

Nice plants TTA!