Fluidized sand bed filter

[+Hydro]

I'm going to build a fluidized sand bed filter for my quaratine system since I won't have much live rock. I really like this idea and it seems really simple to do. This way I can keep my biological filtration outside the tanks and if I treat the tanks I can bypass the filter.

I read that 1 pound of sand can filter 100 gallons of water, that's awesome. Does anyone have any experience with these? What kind of sand is typically used?

I'll post my DIY filter pics here. Basically I'm going to use glass tubes and flate glass for the ends.

[subsea]

I'm going to build a fluidized sand bed filter for my quaratine system since I won't have much live rock. I really like this idea and it seems really simple to do. This way I can keep my biological filtration outside the tanks and if I treat the tanks I can bypass the filter.

I read that 1 pound of sand can filter 100 gallons of water, that's awesome. Does anyone have any experience with these? What kind of sand is typically used?

I'll post my DIY filter pics here. Basically I'm going to use glass tubes and flate glass for the ends.

I would recommend swimming pool sand filter media. While it is silica based, I see no problem.

[+Hydro]

ahhh ok that makes sense

[Timfish]

I've messed with them in the past. They do provide a humungas amount of surface area in a very small space for bacteria to colonize. The issues I found with them is flow is real critical. Too slow and it doesn't agitate the sand well enough, too fast and it flushes it out of the chamber or clogs the screen on the output if there is one. Aquaticeco.com carries both the filter chambers and media.

[subsea]

Steve, this is very agressive nitrate removal. Usually these reverse flow sand bed filters are for intensive fish cultivation.

[+Hydro]

Yes I understand. I've got about 300 gallons in this system and will be bringing in fish to sell so at times there will be a significant load on the system. There is very little live rock and very little sand so besides a skimmers and fuge there would be hardly any other filtration. I'm trying to do everything that I can to keep water changes down to a minimum to keep my overhead as low as possible.

[+Hydro]

I've messed with them in the past. They do provide a humungas amount of surface area in a very small space for bacteria to colonize. The issues I found with them is flow is real critical. Too slow and it doesn't agitate the sand well enough, too fast and it flushes it out of the chamber or clogs the screen on the output if there is one. Aquaticeco.com carries both the filter chambers and media.

I'm going to use a large vessel and only fill it halfway with sand so I can put lots of flow through it without empting it. That is the plan at least.

[Timfish]

That's sounds similar to what I used. They were cylinders about 5" dia and about 24" tall and were about 2/3rds full when water was shut off. I suspect if you use a wide, short cylinder you will need multiple orifices to keep from getting dead spots around the bottom of the chamber. I would think a gate valve will give you better control than a ball valve or butterfly valve over the input flow.

[+Hydro]

My glass tube is 8" x 24", so just a bit wider than what you were using. Maybe I should only run at 50%, seems like that would be more than enough sand for 300 gallons, maybe overkill. I was wondering if I would need to split the flow across the bottom too, I'm not sure one pipe down will be enough either. I may bring the pipe inside the filter then split it in to 4 pipes going down to the bottom, like a small manifold.

This is what I have so far. I cut glass squares for the top and bottom from the busted piece of glass from the tank I repaired. The tube was leftover from another project years ago. I've got a couple of 1/2" bulkheads already and I can get the sand from home depot for $5. Pretty cheap project. I'm having to do this whole QT project on a budget, my wife is about tired of me spending money on the aquarium(s). I can't say I blame her lol

[+Grog]

Hey, you are making something useful and cleaning up all that scrap material. Sounds like a win if you ask me.

[cMidd]

all I consistently maintain is my little nano now, but knowing in a couple of months I'll be in a rental home or appt, everything you post is like food for thought. Keep it up Hydro, Timfish, subsea, And everyone else. I know I'm not the only person reading "from the shadows."

[+Hydro]

thanks! I'm glad that we can all help each other here, makes it all worthwhile.

OK I used all the parts that I had on the shelf and here is what I got done. I still need to make the downpipe with 4 outlets, add sand, test it, then silicone the top panel.

[Timfish]

all I consistently maintain is my little nano now, but knowing in a couple of months I'll be in a rental home or appt, everything you post is like food for thought. Keep it up Hydro, Timfish, subsea, And everyone else. I know I'm not the only person reading "from the shadows."

Thank You! I am really glad to see a lot of discusion on ARCs forums. I also read a lot "from the shadows". I've been keeping tanks for a long time but it's impossible to have enough tanks for everything or enough space for every project I would like to do so reading what other people are doing and keeping lets me accomplish part of my bucket list "virtually".

[Timfish]

. . . I was wondering if I would need to split the flow across the bottom too, I'm not sure one pipe down will be enough either. I may bring the pipe inside the filter then split it in to 4 pipes going down to the bottom, like a small manifold. . .

From what I remember fluidized filters don't need much flow to keep the sand stirred up. I would try a single pipe first and before I did a manifold I would try drilling 4 - 8 holes in a PVC cap glued on the end. If the cap is jetting water across the bottom I would think that would agitate the bottom fairly well. But now that I think about it having tees with branchs going almost to the side would keep the pipe centered in the glass tube.

[+Hydro]

From what I remember fluidized filters don't need much flow to keep the sand stirred up. I would try a single pipe first and before I did a manifold I would try drilling 4 - 8 holes in a PVC cap glued on the end. If the cap is jetting water across the bottom I would think that would agitate the bottom fairly well. But now that I think about it having tees with branchs going almost to the side would keep the pipe centered in the glass tube.

I'll try the single pipe first like you recommended to see if that works. If I split them my plan was to still have all 4 pipes pointing down still, so there would be a pipe running down the center with a cap on the end. Attached to this center pipe would be 4 t's and 4 90's and then 4 downpipes. I was going to put them 1/4" or so off the bottom so the force of the water would go straight out across the bottom. I'll experiment with a couple things, since its PVC it will be easy to change it up if it doesn't work.

[+Hydro]

So I got the manifold built, tried the one pipe and it wasn't enough. I put caps on the pipes and drilled holes in them like timfish suggested. I didn't get much time to experiment with it but I did hook up the manifold to a water hose and it didn't seem to churn the sand as much as I would have expected. I'll play with it a little more tomorrow, maybe I need to drill more holes....or bigger holes.

[Timfish]

I like it. How soon are you setting it up? What are the size holes in the pipe? they look like 1/8 or 3/16 to me. I would be inclined to go with 1/4 or 5/16 the reasoning is whenever the flow is shut off sand is going to get into the manifold and over time "might" cause issues with some of the holes gettting clogged (but I'm just being an armchair plumber ).

[subsea]

You may need higher pressure and volumn from your pump. Tim is right about sand migrating thru holes. Also, over time, the holes will begin to plug with bioligical debris that will have to be mechanically cleaned. To hold large grains in suspnsion requires more velocity of liquid. You may want to experiment with smaller grain size. In any case you will have to balance the flow of the fluid with the weight of the sand grains. I always like having more pump available, marginal does not work well for me.

If you look at the design of a barite fluid transfer system used on drilling rigs, it is very much like what you are trying to do. The flufling spiders are the heart of the design.

Patrick

[DerrickH]

Stephen...you have too much time on your hands LOL! Then again..Im here at work reading up on this stuff so I shouldnt talk huh

[Timfish]

. . . flufling spiders are the heart of the design. . .

So Hydro's just hanging out making flufling spiders . . . wonder if his wife knows why he's not getting her honey-do list done?

[victoly]

I think you've probably got some weird hydrodynamics happening with the multiple lengths of pipes + elbows. Something like this might mitigate that. 2" PVC in with 6- 3/4 inch pieces out.

[+Hydro]

You guys are funny

@ Victoly. I'm actually getting even flow out of it like it is, might seem strange with the way its shaped. We sell manifolds for our chiller systems so I learned lots about them from our chiller manufacturer. Here is some information that you didn't ask for but might find interesting lol. When building a manifold you always want to cap the end of it and branch off to the ports like I did with this one. This way it builds pressure inside the pipe, even if just a tiny bit, and this forces the water out evenly out the tubes (as long as there is enough flow to pressurize). What is critical to making this work is a pressure drop at the end of each port. Without a pressure drop after each port water will flow through the path of least resistance, with even pressures on the ports no matter what the lengths the flow rate will be very close between all.

[+Hydro]

Ok so I drilled out the holes larger, added extra ones, I just simply couldn't get enough flow across the bottom of the 8" tube to "roll" all the sand. I tried different sand too, same result. If I used a larger pump and 3/4" PVC it probably would work.

Instead I decided to scrap the 8" tube and use a smaller tube that I also had laying around. This one is 5" and 30" tall. I reused the top and bottom pieces of glass and just swaped out the glass tube. I will not be building a manfold for this one, straight pipe or straight pipe with a cap on the end with lots of holes drilled in it.

I'm confident this will work better. Its a little taller so I think that I will be able to get the same amount of sand in it that I was trying to use for the large tube. I siliconed the tube to the base today and tomorrow I will go grab a couple more plumbing parts to test it out.

before and after pics

[victoly]

My gut reaction is to buy a bigger pump and just neck down the output. The engineers fuss at you for doing that though

[+Hydro]

I hear ya, that's what subsea said too. I hooked up the manifold to a water hose today with 60 psi of water pressure and it still wasn't enough. It would take 3/4" pvc instead of 1/2" to get the flow up high enough even with a large water pump. I looked up some youtube videos and looked at other people's designs and a narrower tube I think is the answer to get all the sand moving.