Curious about moving bed sand filtration...questions

[Finagain]

I'm pretty happy with canister filters, SunSun in particular, but I ran across some Youtube videos about fluidized sand filters. Supposedly a small amount of sand can filter a fairly large amount of water. It doesn't look like it would be too difficult to DIY a sand filter but I have some questions.What about flow rate? These things take very low GPH to fluidize. Is this type of filter just efficient enough to work without turning over the tank volume as often as other types of filtration? The videos that I've run across have been of submerged setups. Can it work as an outside the tank filter? Any information about them and how to set them up, and what they are best used for would be greatly appreciated. It sounds like they might be something to consider as I get into larger tanks but I don't know enough about them.

ThANKS!

 

[markstrimaran]

They are also called bio reactors, media reactors.
I use a diy, model maybe 60 Gph. With about 2 cups of fine sugar sand.
The slower turn over, does not seam to effect.
I do flow 500 Gph on a 75 gallon thru mechanical filters. The taller the better. 2

 

[duanes]

I use, and have made 3 DIY fluidized bed reactors, one very large, 2 smaller. The reason I call them reactors is, although they do a great job of bio-filtration, they don't do any mechanical. And depending on the type media, they can be used as chemical buffering reactors. I use aragonite as an alkalinity buffering media, beyond its ability to hold beneficial bacteria.
I always use mine outside the tank, and sump (although its not the only way).
I built my largest to be almost 4ft tall and 8" in diameter, it holds about 2 or 3 lbs of aragonite media, and to fluidize that much, a fairly rapid and strong flow was needed (few hundred gallons per hour). When I first built it, it was pressurized with a top.
I found it ws easier to add media later not being under pressure, (I could add media while it was working, and didn't need to shut it off) and removed the top. And during power outages back siphonage became problematic when pressurized, even with a check valve (back flow preventer. These problems stopped when the open top was used.

the reactor is to the left, next to a barrel sump, I used clear PVC to be able to observe the media being fluidized. Aragonite is suspended to about 2ft up the cylinder

 

[markstrimaran]

Their are commercial built units. Phosban reactors, more of a salt water unit, but will cross over well as a sand filter.

 

[Finagain]

I use, and have made 3 DIY fluidized bed reactors, one very large, 2 smaller. The reason I call them reactors is, although they do a great job of bio-filtration, they don't do any mechanical. And depending on the type media, they can be used as chemical buffering reactors. I use aragonite as an alkalinity buffering media, beyond its ability to hold beneficial bacteria.
I always use mine outside the tank, and sump (although its not the only way).
I built my largest to be almost 4ft tall and 8" in diameter, it holds about 2 or 3 lbs of aragonite media, and to fluidize that much, a fairly rapid and strong flow was needed (few hundred gallons per hour). When I first built it, it was pressurized with a top.
I found it ws easier to add media later not being under pressure, (I could add media while it was working, and didn't need to shut it off) and removed the top. And during power outages back siphonage became problematic when pressurized, even with a check valve (back flow preventer. These problems stopped when the open top was used.

the reactor is to the left, next to a barrel sump, I used clear PVC to be able to observe the media being fluidized. Aragonite is suspended to about 2ft up the cylinder

Thanks. Sounds like something I may play with on a small scale to see if it might be worthwhile when I finally go big. How did you determine the flow rate?

 

[duanes]

Flowrates were experimental. I hooked up a Tee to the inflow line to my tank, with a normal PVC valve to adjust flow to the unit.

The pump was an 1800 GPH Mag Drive. I opened the valve gradually until the aragonite became fluidized, but not so much that it was overflowing aragonite particles into the sump.
The plans came from an Article in Freshwater and Marine aquarium magazine, back in the 80s (I believe).
In the article there were plans for large and small versions, the small one was @ 12" tall, with a 2" diameter. If I remember right, they gave estimated flow rates in the article.
Both plans are for pressurized units, which I found problematic.
There were occasional power outages where I lived, and when power went out, sand would get sucked (back siphon) into the unit, blocking outflow, and the largest unit was very heavy, and not user friendly to purge. By keeping the outflow far enough from the top, a pressurized top was unnescessary (hard to screw on and off), making maintenance easy. A check valve helped control back siphon, but not 100%.