Large Capacity Gravel Filter Idea - please discuss

[Desdinova]

I never liked the idea of a sand and gravel filter, because they're layered and seem like they would be very hard to clean without messing them up. This idea came to mind when I was thinking that I could just use the same size gravel throughout the vessel. I figure that the gravel could be about double the size of a pea. In the end, I may have invented or stumbled upon a better way to clean a regular sand and gravel filter, but I honestly don't want to go that route if I don't have to. I want to make this easier and just use the same size gravel throughout. I'm hoping that some people will have opinions and experience to tell me what they're expectations are to it's efficiency.

It has two inputs, because my gravity siphon overflow has two outputs. I figure the pipes will be mounted above the bottom, because the dirt could make it's way down there and get trapped, increasing capacity. In fact, now that I think of it, I wonder if putting a cage under the gravel would help a bit also. It would be a large area where dirt could rest.

The cleaning pipe is intended to stay closed, except those few times per year when I want to clean it. The idea is to attach a hose to the bottom, which goes outside or to a drain, and then running water onto the top of the gravel, washing the unit out. This way, it never needs to be moved. I'm trying to design a system that will hold enough dirt that I won't have to bother with it more than a couple times per year.

I suppose the theoretical capacity and efficiency are going to be dependent on the size of the gravel, the size of the container, and the placement of the pipes. Right now, I only have a 75G tank, so I'm thinking that a 8 - 12 gallon plastic trash container might be big enough to hold 2 - 4 Oscar's waste for many months straight.

The out put of this device will move into a filter bag that will guarantee only the cleanest water gets into the bio filter. The overflow will be kept out. I haven't illustrated it, but that's for another thread anyway. The important point is that a 1 micron filter bag gets clogged very fast. If the water that gets to the top of the gravel filter isn't filtered down to at least 50 microns or so, my bio filter's bag is going to need to be changed quite often... or I'll need a set of bags instead.

 

[David R]

Looks interesting, but I'm not sure why you'd fill it with gravel, is it just for the cost? If you've got a big barrel to turn into a filter like that why not look at something like K1? You'd get far more surface area than with gravel (or the same surface area with half the amount).

 

[Desdinova]

The gravel is present help gravity move and trap the debris at the bottom of the barrel. Thus, the water that makes it to the top is much cleaner. This is not about biological filtration... although that is a significant side effect. Makes me wonder if I just need to plop some pothos in the top of it as a finishing (and denitrifying) touch.

 

[Jc1119]

If its not for bio, it really hard to beat a clean filter sock for mech. Much easier to keep clean imo

and yes, absolutely to the pothos on top. Works very well once established.

 

[Desdinova]

I have a lot of experience with filter socks. I kept trying to get down to 1 micron for the sake of moving the water through Seachem Matrix, but to little avail. Filtering down to that level is very hard. I figure that this system might makr getting there a lot easier. If it can trap 50 microns and larger, I'm already well off. According to my tests, most of the debris that my Oscars produced was 50 microns and larger - but there was a massive amount of it.

 

[Jc1119]

I find a 100- 50 micron combo works the best for large fish. That and Im a fan of the opposite approach to filtration....get it out fast as possible. i don't like canisters or devices that keep waste in the system, because even though I cant see it, it's still in there.

I think you'll trap lots of waste in it, but thats exactly what I don't want to do with something thats difficult to clean.

 

[David R]

If you've got a big drum and want to make a mechanical pre-filter that is easy to clean how about this; http://www.monsterfishkeepers.com/forums/showthread.php?559342-DIY-Radial-Flow-Separators

I think trapping physical waste under a heap of gravel would be awkward to clean, and not particularly effective. I think using some sort of foam as a pre-filter before socks would be a better idea than gravel. I feel your pain about trying to remove waste before the matrix though! Here's my sump, ideally I'd have some socks after the foam, but was starting to run out of room!
http://www.monsterfishkeepers.com/forums/showthread.php?559467-My-sump-and-settling-chamber

 

[Desdinova]

I'm loving the Radial Flow Separator idea. I'll probably have to try that out too. My only concern with that type of solution is the weight of the particles that I want to filter. If that could trap 50 micron particles without the need to make it unacceptably big, that would be a very good option. The water's next stop in the filtration chain is likely going to be a bag filter housing with a 5 or 1 micron bag before the Matrix media.

That said, sand and gravel filters are a tried a true filtration standard. The only real question is what effect using the same size gravel throughout will render. I might just get a bunch of dirty water making it to the top, or a system that doesn't move the water fast enough... but then I could also get a really good filter. Unless someone else has tried this, I don't really know what to expect.

 

[Desdinova]

I'm hoping that my gravel filter will be easy to clean. That's also an unknown. Will my plan of dumping water on top of it and draining from the bottom clean out the waste within a reasonable amount of time? I imagine that I could dump the majority of it initially and then attach a plump with a bag filter to continue pushing particles through it. If I only have to go through that process a few times per year, and I can keep the water toxin free, it'll work. Just depends on how well the matrix is going to be able to control the nitrates. I need as much of the particles removed as possible before I get to that stage.

 

[David R]

What size tank do you have any what sort of filtration system is it running now? If you find filter socks are clogging too fast then I'd suggest lifting them up further out of the water and/or running some sort of pre-filter (even one 200 micron sock inside of a 50 or 5).

The thing with filters that hang onto the waste for long periods of time is that they will working against you if you are trying to control your nitrates. Regular removal of the physical waste will help reduce the nitrates compared to catching it all with a big mechanical filter that then holds it in the water column to continue breaking down for weeks/months.

I don't think a gravel filter would be particularly easy to clean compared to a filter sock, although you probably wouldn't do it as often. If you aren't getting long enough intervals between cleans with the socks then more socks, raising them up further out of the water, and/or prefiltering is the way to go.