Under gravel filtration using a sand substrate...

[jaylach]

I just did that dangerous thing I do at times as in having a thought. Hate it when I do that as it usually gets me in trouble and gives me pain.

Not saying I'm going to do this but, if I find the tank I want for a scud colony, I might.

One of the biggest deterrents for under gravel is that you can't use a sand substrate as the sand will just sift through the slots in the filter plates but why is this true?

I have a picture in my feeble mind of an under gravel filter plate that could work with sand. Why could I not make little 'domes' out of stainless steel or brass mesh and mount the little domes all over the filter plate with silicone. Of course this would leave open slots for sand to still sift through but that could easily be solved by just using some silicone to plug the slots between the mesh domes.

First argument I expect would be that the mesh domes would become clogged blocking water flow but substrat vacuums should prevent this. Cleaning the domes through suction should be easy as, sand being denser, you would only need 1.5-2 inches of sand for this where 3-4 inches of gravel is needed.

Right now this is just a thought but I can't see a flaw. Please be as critical as possible and tell me where I am wrong.

 

[Colin_T]

If you put sand on an undergravel filter plate, the sand will block the gaps or fall through the gaps and the filter won't work properly, or at all.

If you want shrimp or small crustaceans in an aquarium, use an air operated sponge filter in the tank.

 

[jaylach]

If you put sand on an undergravel filter plate, the sand will block the gaps or fall through the gaps and the filter won't work properly, or at all.

If you want shrimp or small crustaceans in an aquarium, use an air operated sponge filter in the tank.

I think that you totally missed the whole concept of my thought. The mesh domes mounted on the filter plates would prevent the sifting of sand through the plates.

Did you actually read my post or just react to the title?

 

[Sgooosh]

I think that you totally missed the whole concept of my thought. The mesh domes mounted on the filter plates would prevent the sifting of sand through the plates.

Did you actually read my post or just react to the title?

since sand is so thin, it will easily block the small holes of the mesh and still make it hard for the filter to work.
i use a giant power filter with tiny fish and to solve the issue of baby fish and snails getting sucked in i just put sponges on the outside of the filter. easier to clean as well.
do you know how at the beach when you make a small hole, it takes a very long time for water to seep through and fill it? that is what i mean

but for gravel, the water barely has resistance

 

[jaylach]

since sand is so thin, it will easily block the small holes of the mesh and still make it hard for the filter to work.
i use a giant power filter with tiny fish and to solve the issue of baby fish and snails getting sucked in i just put sponges on the outside of the filter. easier to clean as well.
do you know how at the beach when you make a small hole, it takes a very long time for water to seep through and fill it? that is what i mean

but for gravel, the water barely has resistance

I understand what you say about the sand being fine and blocking the mesh but I think that a fine micron mesh could prevent this. Also I would think that weekly substrate vacuums would keep the sand loose to help allow water flow. Also I think that some stem plants in the substrate would help with the roots going over the mesh domes and helping water flow.

I asked for critical responses which is what I'm getting and I appreciate that. Still I'm not convinced. If I end up following through with a 5 gallon fresh water scud tank I just may try this. I mean what would I possibly stand to lose but a 5 pound bag of sand and a $10.00 USD scud culture? I think that it would be an interesting experiment.

 

[Sgooosh]

I understand what you say about the sand being fine and blocking the mesh but I think that a fine micron mesh could prevent this. Also I would think that weekly substrate vacuums would keep the sand loose to help allow water flow. Also I think that some stem plants in the substrate would help with the roots going over the mesh domes and helping water flow.

I asked for critical responses which is what I'm getting and I appreciate that. Still I'm not convinced. If I end up following through with a 5 gallon fresh water scud tank I just may try this. I mean what would I possibly stand to lose but a 5 pound bag of sand and a $10.00 USD scud culture? I think that it would be an interesting experiment.

that's a good point. perhaps you could also get mts in the tank (if scuds dont hurt them)
you could also have an undergravel air pump to loosen it 24 7
im not concerned about sand blocking the mesh, just the sand itself being a medium that water flows so slowly through

 

[jaylach]

that's a good point. perhaps you could also get mts in the tank (if scuds dont hurt them)
you could also have an undergravel air pump to loosen it 24 7
im not concerned about sand blocking the mesh, just the sand itself being a medium that water flows so slowly through

Sorry but I'm old and don't get all abbreviations. Could you define MTS? Somehow I think I should know but don't.

Yes, I fully understand that sand is much denser than gravel and would restrict water flow but that MAY be self solving as the sand density would mean that no more than half the depth would be needed. With gravel you want 3-4 inches. With sand I'd bet you could get the same results with 1.5-2 inches.

Not a direction I think I want to go but there could even be argument made for reverse under gravel filtration for a sand substrate. There is a guy in a local aquatics group on Face Book that absolutely swears by this for crustacean tanks but but I think he is using gravel.
<edit for self correction>
Reverse UG filtration would not work with sand as it would necessitate not using the mesh domes as they would clog from the bottom and a siphon could not clean. Without the mesh domes sand would then sift to under the filter plates further blocking water flow.

Hey, if I try this with a 5 gallon scud tank I already have nylon mesh to keep the sand from sifting through the plates that, if I remember right is 5 micron. Could not use to make domes as it is soft and flexible bit I sure could sure use to keep sand from sifting and substrate vacuums could keep clean enough for water flow. Yes 5 micron is fine enough to restrict water flow just on its own but I always overkill air flow for UG. If I did this for a 5 gallon scud think I'd probably use a Whisper 20 to drive the air risers which would be rated for a 20 gallon tank. Shoot, even using gravel as my substrate in my 20 gallon I use 2 separate filter plates with each plate driven by a Whisper 20 when one Whisper 20 is rated to handle the entire tank. I really DO think this could work well. Shoot, just looking at my main tank... when I do a major water change I end up with the air risers 3-4 inches above water level and they still push water. Using a Whisper 20 in a 5 gallon would equate to twice (actually may be 4 times) the air in relation to my dual Whisper 20 pumps in my 20 gallon using gravel. Considering half the substrate depth using sand I just can't see an issue. I just think that the air I would push would pull water through sand.

 

[GaryE]

Try it.
I'm not convinced it won't clog, but I also wonder about the grain size you'll use. One person's sand is another's fine gravel. I use pool filter sand as substrate, but to me, it isn't sand except in the writing on the bag. It would clog an undergravel, but it could be worked around. You would have to make your own UG. It seems your solution and making a UG are a lot of work for the return.

 

[Back in the fold]

Two or three layers of cotton cheesecloth over the UGF plate before the sand. Simple.

 

[WhistlingBadger]

I'd be interested to see this play out. I tend to agree that it's a lot of work for the result. Why not just stick with gravel?

Rather than cheesecloth, which will eventually rot, why not just cover the plates with a thin layer of filter floss? That's what I did with the planters in my paludarium: Lined the bottoms with stainless steel mesh, then put a bit of filter foam in them to hold the sand in but still allow roots to penetrate. Seems to be working.

 

[Byron]

I think the actual purpose of filtration would be lost. The idea behind an undergravel filter is that detritus is drawn into the gravel, and waste bacteria break it down. Sand is a better substrate than gravel because it provides more area for this to occur. There are basically no bacterial issues with sand as opposed to gravel; these bacterial issues are on of the major reasons that Corydoras should never be over gravel but always sand. It is a healthier substrate.

Doing what is suggested in post #1 would, if I read this method correctly, not provide biological filtration at all, or not as much, whichever. The whole point of the undergravel filter providing a good bed for the bacteria is lost.

With a sand substrate, and provided all else is equal, you do not need to touch the sand and it basically maintains itself. I had a couple tanks where this occurred over several years. I also had undergravel filters in several tanks some time ago, including a 90g tank, and I was continually having to siphon the detritus out from under the filter plate.

 

[Back in the fold]

I like @WhistlingBadger what he said about filter floss instead of cheesecloth. That’s a way better solution and also a guy can buy various filter media in sheets. Carbon , zeolite, I think it’s called, and other stuff. Those would block the sand from sifting down the UGF slots. This is an idea I’ve been thinking about too. Maybe it’s a good idea or maybe it isn’t but you never know until you try. Under gravel filtration has a lot of benefits and is NOT an outdated method at all. Think about this - a creek flows along and the water is running through the rocks , sand , gravel and whatnot on the creek bed with the current. That’s under gravel filtration.

 

[kiko]

this is my new unfinished tank with a double sump...will eventually have pool/sock filters on both sides on a flower pot and holes at the hole/plate level on both sides
this allows for fish/shrimp of any size to get in into the filter partition but being split in double the "suction" power would be less on either side
and allow them to freely travel in and out....
maintenance is as simple as removing a small rack with sponges from both sides and switching them out instead of redoing the tank after a certain time like an undergravel

 

[GaryE]

If you use filter floss, why not just use a large volume box filter and forget about the undergravel aspect? Box filters work well.

Or look into sand filters. I think the discussion is veering into fixes that undermine the idea - put square wheels on a car and it won't use gas.

 

[Back in the fold]

@jaylach wants to have sand over an under gravel filter in an aquarium that he does not yet have which he will raise Gammarus Scuds in. He has correctly assumed that the sand will sift down through the plate slits and he’s wondering how to overcome that. I get it. It makes sense to me because you wouldn’t have Scuds trapped in a filter and they will be easier to catch. Several ideas have been advanced that just might work and I hope they do. Haven’t any of you folks ever had an idea you wondered about ?