Undergravel filter gravel depth

[rsol44]

What's the reasoning behind the 2-inch recommendation on gravel depth for undergravel filters?

I imagine that if you have two much gravel, water flow through the gravel will be too weak or nonexistent.

If you have too little gravel and the filter plates are exposed, water will flow through the opening rather than through the gravel.

So how is 2-inches the right number? It seems to me like 1 inch is enough gravel to cover the filter plates and not too deep that you won't get good water flow through the gravel.

 

[coach_z]

To answer your question: An average depth of 2" is good.

My opinion: Under gravel filters are the devil. They are a pain to maintain, setup, operate, clean, use, etc. I will never use one again, will never recommend them, and will always suggest that people remove them at their first opportunity.

 

[excuzzzeme]

Having used UGF in the past, I won't use them again. For me they are too much a PITA. I prefer wet/dry as much as possible, second option is the sponge filter. JMO.

2" of gravel was established as being the ideal amount.

 

[kj5kb]

What's the reasoning behind the 2-inch recommendation on gravel depth for undergravel filters?

I imagine that if you have two much gravel, water flow through the gravel will be too weak or nonexistent.

If you have too little gravel and the filter plates are exposed, water will flow through the opening rather than through the gravel.

You've got the idea.

IMHO 1.5-2" is good. I was looking at one of mine this morning that has 3" and thinking...Gee I need to take some out of there.

I'm not a big fan of standard UGF, where the water flows down through the gravel into the plates and up the tube.

Reverse flow undergravel filters (RUGF) are the opposite; the water is pushed under the plates and up through the gravel. IMHO these work well.

I have been using reverse flow undergravel filters for years with good results. I use Penguin 660r powerheads to drive them, multiple powerheads per tank depending on size of tank and bioload. One on a lightly loaded 20H, four on a 90G. I usually supplement them with an HOB or sponge filter to get some water movement/aeration.

One nice thing about RUGFs...they are very quiet compared to an HOB or any air-driven filter.
Even with 4 powerheads going, the 90G is REALLY quiet. I have a 40 with 3 powerheads and an HOB in a spare bedroom; when we have guests I just unplug the HOB.

For gravel I use the all-purpose gravel available next to the concrete (not the garden section). It's ugly in the bag , but it cleans up nicely.

Depending on the size of the slits in the UGF plates, I may screen the gravel with 1/4" mesh hardware cloth and just use the larger stuff.

 

[toddnbecka]

It's a combination of suitable size gravel and total surface area for bacteria to colonize. I use a couple set up reverse-flow with powerheads, and had them in a 55 for years using aquaclear hob filters connected to the uplift tubes. Either way, debris doesn't accumulate under the plates, and the hob's collected whatever made it through the gravel.

 

[ODPILOT]

I agree with the above people. Under gravel filters are not good. The gravel ends up harboring rotting fish food and poop which supplies an endless source of ammonia and other pollutants. The food and poops do not miraculously dissapear -- they are always in the gravel and lots of under gravel filters trap a brown, rotting sludge underneath the plates which then causes the water to turn brown and stink. Stick with an outside and/or cannister filter where every month, the rotting material inside the filter floss will be thrown out. Sorry

 

[Rbishop]

UGF are great...if you are dedicated about maintenance and do not overfeed. RUGF are even better, and with proper flow from power heads or canisters, can't be beat.

Most folks who tell you either are bad fall into on of two catagories..without fail...

1) To lazy to maintain the filtering option correctly

2) Have never maintained tanks with either and are just repeating stuff they have read and do not have any experience with

 

[apolloobserved]

Total agreement with ODPILOT. Too add if you have plants-don't use UGF. The two don't mix. The 2inch rule is probably to try to allow circulation? what kind of UGF (brand)? Penplex? I have had UGFs and canisters. I had UGFs back in the 70s and had one about 5 years ago. UGFs are old school.

 

[fishorama]

As I've said before UGF is a PITA to maintain especially with plants. They love it but roots tangle in the plates. I wish I'd have tried RUGF back in the day, I may still try it at least once...

 

[jpappy789]

When will the fear mongering end with this subject?

I am always with Rb on this one...having used a UGF turned RUGF system in the past I've yet to see issues. Planted it too. Had some hardcore Cryptocoryne roots but never once saw any indication that the plants or the system were harmed. It isn't the easiest to re-scape though if plants are really established. I never moved those crypts, to be quite honest.

My gravel was probably closer to 1.5" deep but I never really checked.

Never had any ammonia spike...no brown, rotten water...no sludge...seriously, just vacuum the gravel weekly like most people recommend anyways and you will be fine. Even better would be to go the reverse route if you are at all worried. I found it to be a more efficient system anyways especially when ran in conjunction with another filter (HOB, canister, etc.)

When I tore down the tank I found some tiny bits of gravel that got sucked through and shreds of plant roots that I did try to move. Then again they always seemed to recover anyways.