HOW

Which bio-filter to use in my new RAS

148 posts in this topic

I am in the planning stage of a new RAS. I have been reading my Small Scale Aquaculture book and it has answered a few of my unknowns. It has also raised some new questions.
Having had an aquaponics system running for a little over 2 years, I thought I knew what I was getting into. Nope, this is a new game. So, now I am wondering what to use as a bio-filter. Van Gorder suggest that his RBC is the way to go with a 2000 gallon pool, but he uses 2 55 gallon clarifiers.
I am thinking of using a 12 ft. (2000 gal.) above ground pool to raise blue tilapia in central Florida. I was planning on using a 55 gallon radial flow filter for the solids, a 150 gallon Skippy filter for the ammonia and nitrites and a separate tank growing duckweed for the nitrates. My main objective is to avoid water changes. What do you guys think?

:phone:

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I would use a moving bed filter for the biofilter in a 55 gallon drum vs. the RBC's. I really like the RBC's and have built three of them as per Van Gorder's book but they are expensive to build and really should be in a seperate tank to work effectively, as having them in the same tank as your fish will cause them to build up with fish waste. Just materials from a big box store for one RBC is about $500.00.

With the moving bed in a barrel all you need is a 55 gallon blue drum, a membrane diffuser, a few fittings, and the media. You can use up to 4 cubic feet of media in a drum. Cost depends on how much media you need to use. I use MB3 media from WMT in Louisiana which is half the price of Kaldnes. The moving bed tank also takes up less space than an RBC.

http://www.w-m-t.com/Products/WaterTek_MB3_Moving_Bed_Media.php

I don't think you can get away from water changes as you will have to clean the filter material off.

Not a big fan of skippy filters. The drum filters (Clarifier in a drum packed with orchard netting using a siphon as in VanGorder's book) work like a champ for me and are easy to clean with a garden hose.

However my tanks are not 12 foot or 2000 gallons. Biggest tank I have is about 600 gallons.

Edited by Cecil (see edit history)

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Howponics,

 

Here is a good DIY moving bed filter used for a koi pond:

 

http://www.koiphen.com/forums/showthread.php?69028-Birdman-s-Fluid-Bed-Filter

 

Here is one of mine in this thread that uses smaller fittings, mostly Uniseals.  The one's I build now use a bulkhead fitting in the bottom. If you install a Uniseal or bulkhead fitting in the bottom center of the tank to attach your membrane diffuser be aware of the fact that some tanks have a very pronounced center ridgeline that can cause you issues with a good fit.

 

http://aquaponicsnation.com/forums/topic/8826-filter-media/

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Although I would enjoy the challenge of building one of Van Gorder's RBCs, I am convinced that a moving bed is the way to go. Now the problem is deciding how much filter I will need. So, if I have say a 3000 gallon pool and I want to harvest 500 lbs of tilapia how big should I build the MBBR? I know there will have to be some type of clarifier before the MBBR, maybe a couple in series.

I upped the size of the pool because we would like a bigger harvest. Van Gorger's book suggest that the 12 ft. pool was only good enough for a 100 lb harvest and that just doesn't seem to be worth the time and energy. And I am confident that the density can be higher than 1 lb/20 gal.

I am open for suggestions.

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HOwponics,

The thing you have to realize with VanGorder's system is it isn't self cleaning (no center bottom drain) as he had to simplify things for the average Joe. A bigger volume of water, with a lower density of fish is a safety net for less experienced people. In the pool in Steve's book, I shutter to think of all the solids that were sitting on the bottom, although I'm sure the fish movement was resuspending it somewhat to be sucked up by the siphons. Of course tilpia can handle it, and I am in no way downplaying VanGorder's system. I've learned an incredible amount from Steve's book and still use the clarifier tank and siphon to agreat advantage. I love the siphon for it's effectiveness, simplicity, and the fact that it bascially runs off of gravity.

I've had 1/2 pound per gallon of a less forgiving species like Yellow Perch in a 170 gallon tank with no problems. However my tank does a good job of removing settleable solids with the center drain and the circular movement of the water that pushed the solids to the center drain to be purged. It's more difficult to get that self cleaning action with a larger tank. You need more flow to do it hence a bigger pump and higher energy costs.

I am able to fit 4 cubic feet of media in my 55 gallon (208l) drum mbbr. Your best way to estimate carrying capacity of your filter size is to go by how many pounds of feed you feed per day. That would be the neighborhood of 0.6 to 1.2 lbs. of feed per cubic feet of media. As far as fish lbs. a good rule of thumb and a bit conservative is 47 lbs. per cubic foot of media. This of course optimum water temps for the bacteria in 25 to 27 C. range. Lower temps would need more media.

So one moving bed filter with 4 cubic feet of media would be 47 lbs. X 4 cubic feet which would come out to 188 lbs. of fish upon harvest.

Personally I would not try 500 lbs. of fish for your first attemp at aquaculture.

I'm confident I can produce 300 lbs. of fish in my 600 gallon aquaponics tank using just an airlift and 60 watts of electricity. 300 lbs. of fish is a lot of fillets!

Have you consider adding in a raft tank and allowing your biofilter to overflow into it via gravity? As long as your raft tank is higher than your fish tank it dumps back into the entire system will run on a small mag drive pump that sits on top of your clarifer tank(s). Of course you will have to elevate your biofilter tank a little but that's not a big deal as your mag drive pump will pump into it anyway.

Edited by Cecil (see edit history)

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It didn't escape me that Van Gorder failed to mention much of anything when it came to lifting solids from the FT. I am actually looking to someone with a pool in their aquaponics system to give me help getting the solids out of the tank. But I see what you mean about him not wanting to overload someone with little or no experience. The book too was aimed at the folks in a temperate zone and that doesn't pertain to us down here as it rarely stays real cold for very long.

 

I have used U syphons and they do work well. Using a 3 inch pipe IMO would do a much better job than the 2 inch. But I guess that goes without saying.

 

I won't argue with you that 500 #s is a bit much for the first go around. But it is a target and I hope to be there by the second go around. So, based on the figures you have provided for me, to get close to that number I am going to need something larger that a 55 gal. drum. Maybe I need to reconsider a 150 gallon skippy filter.

 

I have considered adding another tank, but not for rafts. I think a trough full of duckweed would serve as a feed source for the tilapia and it would get rid of a good amount of NO3.

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A great place to get ideas believe it or not is the Koiphen website that deals with koi.  Some folks have swimming pools for quarantine tanks and at least one poster raised hers with polystyrene sheets and put in a center drain. Another option is what they call a "retrodrain" which doesn't require a hole in the center or even the side of the pool.

 

The DIY section has a lot of cool ideas and in reality they are running recirculating systems, with the exception their fish are at a lower density and they want gin clear water.  You should also take a look at Birdman's sand and gravel filter for simplicity and a polishing filter after a primary filter. I will use one or more of these DIY sand and gravel filters when I set up my coldwater partical recirculating system for trout inside a building at some point in the future. It seems like an economical way to create the gin clear water that trout require and it's easy to clean with a blower.

Edited by Cecil (see edit history)

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It is raining and I am sitting here at work with little to do, other than listen to the wheels turning in my head.

 

Eventually I would like to have 2 pools (12' or 14') side by side and be harvesting close to 1000 lbs. of tilapia. I am thinking I could use an IBC with 21 cu ft of K1 as my bio filter for both pools. Each corner of the IBC would need an air defuser to keep it all churning. The fish pools would discharge into individual clarifiers, then from the 2 clarifiers into the MBBR. From the MBBR the effluent could flow into a sump and be pumped back into the pools.

 

Its still raining.

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It is raining and I am sitting here at work with little to do, other than listen to the wheels turning in my head.

 

Eventually I would like to have 2 pools (12' or 14') side by side and be harvesting close to 1000 lbs. of tilapia. I am thinking I could use an IBC with 21 cu ft of K1 as my bio filter for both pools. Each corner of the IBC would need an air defuser to keep it all churning. The fish pools would discharge into individual clarifiers, then from the 2 clarifiers into the MBBR. From the MBBR the effluent could flow into a sump and be pumped back into the pools.

 

Its still raining.

 

 

You could get twice the bang for your buck using mb3 from Water Management Technologies in Louisiana at half the price of K1.  21 cubic feet of media can really add up in price.

 

Sounds like a plan to me.

Edited by Cecil (see edit history)

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Then MB3 is it. I think I will call Baton Rouge tomorrow for a quote. Maybe they have had experience with someone using an IBC as a MBBR.

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After some research I have settled on what I think will work for what I am wanting to do. I will accept any thoughts. In a nutshell here is my plan.

 

Starting with the tanks, I plan to use two 12 ft. x 36" above ground pools. I have been shown a method of using the side skimmer as the tank drain. It works. From each fish tank the flow will go into individual standard 55 gal. RFF and then from there flow into the bottom of a 55 gal. swirl filter. In the swirl filter the flow will move upward through 12 inches of R-Matala filters, 1 green and 1 blue. The flow from both swirl filters will enter into a single moving bed bio reactor, using a 275 gal. IBC with 21 ft3 of MB3 bio media. Now I need to remove some of the nitrates. To do this I want to use a sump tank (or two) with duck weed or some other aquatic plant growing on the surface. The flow could enter the sump from below, to avoid disturbing the surface, and from there be pumped back into the tanks. Each tank would have separate pond pumps, in the sump, to avoid flow issues. Air to the filters and both tanks will be supplied by a S31 Sweetwater blower to maintain high DO.

 

Tilapia are easily permitted in our area, so there will not be any legal issues. In fact, several varieties of tilapia are allowed in tanks here. That and the fact that tilapia are very tolerant to poor water quality will give us an opportunity to learn as we go. I have had blue tilapia in my aquaponics system now for a while and they have done okay in my care. We hope to harvest a few hundred pounds from each tank the first season.

 

I will post some pics as the projects begins to develop.

Edited by HOWponics (see edit history)
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Well the system build is complete, with only a few changes from my plan presented in Post #13. The air blower was upgraded to a S41 per Pentair's recommendation. Way plenty of air, although I make no mention of it in the video I made. The bio-media I am trying is polypropylene shavings from a broom manufacturer. As of this post the system has been running nearly flawlessly for about two weeks. I am not a video master, but here is what I've got:

 

ande and crsublette like this

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That's pretty intense and i think it's well executed.

 

Was the broom shavings free for you? 

 

Your water is already dark, is that well water?

Edited by bcotton (see edit history)

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That's pretty intense and i think it's well executed.

 

Was the broom shavings free for you? 

 

Your water is already dark, is that well water?

The broom shaving are a donation from a friend in the plastic industry. This farm is set up as a 501c3. And yes, the water source is from a well.

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Hi HOWponics,

 

Innovative use of the plastic shavings.  I hadn't thought about using shavings in quite that way before,

 

This system is larger than your average family would need.......more like that for a commune, or an intentional village community.  What is a 501c3?

 

Gary

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Gary,
 
I'm sorry, you wouldn't be expected to know what a 501c3 is. It is an American term referring to a special Internal Revenue Service (IRS) code given to organizations who give assistance to underprivileged people, among other purposes. This farm is owned by a ministry, Answered Prayer Ministry, that donates food and clothing to the needy. We intend to donate a portion of the harvest, but we also will be selling a good portion of the harvest in order to further our cause in the ministry. Thus the size of this system being larger than normal.
 
As for the media, we were offered these shavings as a (tax deductible) donation. I was not sure about it at first, but decided to give it a try. I filled a bucket with water from my aquaponics system, alone with some gravel from one of the beds and an air stone. At first all of the media simply floated, as it should have. Within a few days the media began to "boil" with the air flow and I was convinced we were on to something. This media is large enough that it will not pass through the slits in the drain, so it will be easily contained within the filter.

 

I would be happy to post some pics if someone can tell me how to upload images to My Media.

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IMHO, the best way to upload pictures is to the thread itself... near the "post" button is a "more reply options" button.. click that and "Attach files" will show up  at the bottom right of your text window and you can just browse your file system and attach them

Edited by bcotton (see edit history)

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Okay, thanks bcotton. I just learned something.

 

Here is a look inside the biofilter before adding water and media. There are five 12 inch air difusers near the bottom. The inlets, as well as the drains, are connected by a section of 3 inch pvc with sufficient slits cut into them on all four sides to allow free flow in and out of the filter. The media had to be large enough not to pass through the slits. Both of the 12 foot tanks flow through this filter. It remains to be seen if that was a good idea.

 

post-3618-0-10222500-1410481249_thumb.jp

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Wow that's quite the filter! I'm impressed! Don't see why it won't work well as long as you remove solids before getting there, the media tumbles well, it stays well aerated with no dead spots, and you have ample surface area for your feed load.

Can't wait to see a video of it in action if you don't mind.

The only possible downside (and It may not be a problem) is the choice of stones over membrane diffusers that are self cleaning for the most part. The stones may need to be removed at intervals and cleaned with muriatic acid. Or perhaps I'm wrong?

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Wow that's quite the filter! I'm impressed! Don't see why it won't work well as long as you remove solids before getting there, the media tumbles well, it stays well aerated with no dead spots, and you have ample surface area for your feed load.

Can't wait to see a video of it in action if you don't mind.

 

I am fairly sure I have those bases covered Cecil. No way for me to calculate the surface area of this media. It's like little black plastic screws, plenty of surface area and they tumble great after a day or two in the tank. I will upload a video after it is fully loaded.

 

Now i am cycling the system. Maybe I should start another thread on this topic. Anyway, it is going rather quickly, I think. I seeded the filters using 4 sponge filters that I kept running in my established aquaponics system for about 4-5 weeks. A 5 gallon bucket sampling told me that it would require a full quart of ammonia to bring this system up to 5ppm. I use Ace Hardware's brand because there are no additives. That seemed like a lot of ammonia, but this system has +/- 4900 gallons capacity. On day 6 the nitrite began to spike and on day 9 it began to show signs of nitrate. As of yesterday, day 10, ammonia was down to 2ppm, nitrite was up to 1 ppm and nitrate was getting close to 1 ppm. This afternoon I am looking for a drop in ammonia and nitrites.

 

Should I continue to dose the system with ammonia to say 1 ppm and watch for a quick drop back to zero? Maybe it's different for a system this large.

 

The system quickly loaded up with algae in just a matter of  a few days, where there was none before. I take that as an indication of nitrogen in the water.

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