Best Undergravel Filter

SFKINNC · Jan 30, 2019

To build a DIY under gravel filter, I suggest using plastic “egg crate” light diffuser grids cut to the size and shape of your aquarium. Lift them off the floor of the aquarium using squares cut from the egg crate itself or use stones or use short lengths of pvc pipe. Use enough pieces to support the weight of the grid and the gravel. Cover the grid with either fiberglass window screening or with plastic needlepoint canvas (available at sewing shops or craft suppliers). There are several ways to arrange the flow. I have used PVC pipes to create the “lift” tubes. Cut the bottom ends of the pipe at a 45 degree angle so that water will be able to flow under the egg crate. After cutting the pipes to length, cut holes in the egg crate for the pipes and fasten the pipes in place with nylon zip ties. Cover the grid with your choice of gravel (NOT sand). For water to flow down through the gravel and up through the tube place a powerhead on each tube so that the cone shaped strainer/adapter rests on the tube. For water to flow down through the tube and up through the gravel you will have to adapt the powerhead to work in the other direction. In one of my tanks where there is no danger of small or soft critters getting sucked into the powerhead, I simply drilled a hole in a plastic bottle cap that fits tightly into the lift tube, placed the outflow spout of the powerhead through the hole and slid the bottle cap into the lift tube. The cone shaped strainer of the powerhead by itself is safe enough with large fish and critters that can’t get sucked into the powerhead. But you can cover the strainer with a sponge filter cut to fit. Alternatively, Marineland makes a kit, complete with sponge prefilter, that makes it possible to attach a Penguin powerhead (might fit others - I really don’t know) so the water flows down the tube (about $12).

I have made the undergravel filter for my 75 gallon hex tank using the bottom of a plastic bucket. I drilled a zillion holes in the botom of a 5 gallon bucket, cut away all but two inches of the side of the bucket, turned it upside down, inserted PVC lift tubes and added powerheads. I also used a couple of pieces of PVC to support the center of the bucket and the gravel above. Hope my ideas help.

UG filters are not as popular as they once were, BUT that does not mean that they don’t work and work well if you clean the gravel periodically. Of the 9 tanks I’m currently operating, three are using under gravel filters now and I am converting a fourth to under gravel this weekend. I find they are easier, require less work cleaning and do not require expensive cartridges or bags, or DIY substitutes for manufactured cartridges and bags.

William Buchanan · Jan 30, 2019

Thanks! I believe it’s worth a try! I’ll start working on it!

William Buchanan · Jan 30, 2019

Paul B said:
I actually do not have a thread on that because there are maybe 3 people in the world that use them. They just happen to be the three oldest tanks in the world.
OK, I am guessing. But you get the filter and throw out the tubes. Then you have to get all three or four tubes to come up in the same place. You can use acrylic, or PVC but you really should have something you can see through. I think I may have used the tubes that came with it and put on PVC elbows.
But however you do it I have all the tubes coming into the bottom of a plastic container just above the water. I have a pump in the tank pumping water into the container but if you have a sump, you can use some of that return water to go in there. But you should run it slow, like 150 GPH down each tube.

This is an old one but you can see 3 tubes coming into the bottom. The other tube comes from a pump behind the rocks.

Thanks Paul! Do i need to put coarse sand/gravel only? Can I layer it?

SFKINNC · Jan 30, 2019

If the gravel is too fine, there will be no flow through it. I use course (3-5 mm) gravel for freshwater or salt.
For saltwater I use crushed coral, dolomite, or crushed oyster shells to stabilize the pH. For freshwate I use pea gravel from Lowes.

William Buchanan · Jan 30, 2019

Thanks!

Paul B · Jan 31, 2019

William Buchanan said:
Thanks Paul! Do i need to put coarse sand/gravel only? Can I layer it?

Do not layer it. that will only last a week. The best UG filters have slots and the slots are wider the farther away from the tubes they are. If all the slots or holes are the same size 100% of the water will just go through the gravel right near the tube. The different size slots allows for a more variable water movement.
My gravel is this size. Kind of as large as rice.

Matt Carden · Jan 31, 2019

JoshH said:
@Paul B might be your best source of info on UGF's he still uses one in his setup and while yours is freshwater(which arguably has a better use of UG filters) I'm sure his info works in both cases.

@Paul B 's UGF is 47 years old I doubt they still sell those

Paul B · Jan 31, 2019

I moved here 7 months ago and bought a New UG filter. It seems to be designed pretty good although it is thinner and cheaper than my old one.

SFKINNC · Jan 31, 2019

My experience with UG filters has been that they tend to be cheaply made, but that they last long time. Eventually just about any plastic will dry out and disintegrate, but the environmentalists all seem to say that it takes a heck of a long time. Silicone sealer or Shoe Goo can be used to repair small cracks and attach supports under spots that sag or to reattach adjoining plates or even lift tubes that break free of their anchor points. I have also used zip ties and tied plates together with flexible airline tubing. I imagine that the newer more flexible silicone tubing will make tying things together for underwater use even easier than before.

William Buchanan · Feb 3, 2019

Paul B said:
I actually do not have a thread on that because there are maybe 3 people in the world that use them. They just happen to be the three oldest tanks in the world.
OK, I am guessing. But you get the filter and throw out the tubes. Then you have to get all three or four tubes to come up in the same place. You can use acrylic, or PVC but you really should have something you can see through. I think I may have used the tubes that came with it and put on PVC elbows.
But however you do it I have all the tubes coming into the bottom of a plastic container just above the water. I have a pump in the tank pumping water into the container but if you have a sump, you can use some of that return water to go in there. But you should run it slow, like 150 GPH down each tube.

This is an old one but you can see 3 tubes coming into the bottom. The other tube comes from a pump behind the rocks.

I decided to go with powerheads to pump the water down the tubes. Turns out a 1/2” murloc union is a perfect snug fit joining the powerhead and the down tube. I’ll have to experiment with flows and number of tubes/powerheads to use to keep it on the slow side. The Lee’s UGF has two halves for a 75 gal (48x18). I will try one tube each side to start.

For gravel im planning on using caribsea natural reef which is 5mm.

Paul B · Feb 4, 2019

Very slow flow is best. I experimented for years

William Buchanan · Feb 4, 2019

It should come out to 150 per tube if I were using 4 tubes. But I’ll only be using one tube per half but at 300 gph. I may end up changing if I can’t get it slow enough. Thanks

garbled · Feb 4, 2019

There is a guy on youtube, I think "the fishman" or something, who makes a bunch of crazy DIY parts out of acrylic for freshwater tanks. Anyhow, I know he has like 5-6 videos about UG filters, because he has been doing a bunch of experiments with them on various tanks, trying out different designs, etc etc.

William Buchanan · Feb 4, 2019

Thanks, I’ll try to find them!

hikermike · Dec 30, 2023

Not to resurrect a dead thread but then again...... I'd like to make 2 or 3 or 4 points.... 1., I like to use UGF in all my new setups as they allow me to cycle a NEW tank in 3 days. None of this waiting around checking ammonia levels etc. Usually have to check 4 or 5 and I'm good to go. 2., To achieve this you don't have to cover the entire tank bottom with plates. Just a part. This allows you to heavily aquascape part of your tank and then when well established Remove the plates from part of the tank not scaped if you find the tubes etc. unsightly. 3., When you first set it up make sure you place the uplift tubes and airlines at least 2-3 inches away from a wall. This will allow you to get your cleaning equiptment in to clean the algae without disturbing the tubes or plates which can be awkward to replace. 4., Everyone who complains about them mentions poisonous gas buildup as a detraction but in70 years of having tanks and using UGF's I have never had this happen nor heard/read of any time this has actually happened to someone. It's only a theoretical probability in my opinion. The substrate in my tanks are often 6-7 ' deep as I like diggers.