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DIY Fluidized canister filter finally sealed and churning... thoughts?

Cal Amari said:
What tanks, gallons, livestock etc are you trying to run with this?
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It's a 55gal with 18 young Mbuna.

I am under-filtered right now with a single cascade 700 canister but getting by because of small fish and good filter media. I want to add a shoal of catfish, and a tank upgrade is in the works for the future, so playing with filtration ideas now before it becomes a situation.

This 4gal container of fluidized media gives >250 SQ ft of media surface area vs the <50 SQ ft of 30ppi foam I have in the canister now.
 
Hmmm, well I'm no expert on filtration but for a 55 with mbuna, even at 18 and adding catfish I can't imagine needing a fluidized reactor. There's lots of threads here about people trying to figure out maximizing surface area and cramming as much biomedian as they can into a filter, but from my limited experience, and comments from other very experienced aquarists such as @duanes, i believe once a tank is fully cycled it's a fairly small amount of biomedia actually needed, the bacteria only expand to the size of bioload provided, and they won't expand beyond that despite how much media is there. If you're still having ammonia or nitrite readings after maybe 6 months of operation then perhaps you need more biomedia, but less time could mean your cycle just isn't complete, or if it's nitrate you're worried about, bio won't help. Water changes and plants are the only solution. Or if water clarity is the issue then you need more mechanical filtration.

Anyhow still a cool experiment and contraption to get working, but You might need to clarify the specific filtration issue to see if you're solving anything.
 
Cal Amari said:
Hmmm, well I'm no expert on filtration but for a 55 with mbuna, even at 18 and adding catfish I can't imagine needing a fluidized reactor. There's lots of threads here about people trying to figure out maximizing surface area and cramming as much biomedian as they can into a filter, but from my limited experience, and comments from other very experienced aquarists such as @duanes, i believe once a tank is fully cycled it's a fairly small amount of biomedia actually needed, the bacteria only expand to the size of bioload provided, and they won't expand beyond that despite how much media is there. If you're still having ammonia or nitrite readings after maybe 6 months of operation then perhaps you need more biomedia, but less time could mean your cycle just isn't complete, or if it's nitrate you're worried about, bio won't help. Water changes and plants are the only solution. Or if water clarity is the issue then you need more mechanical filtration.

Anyhow still a cool experiment and contraption to get working, but You might need to clarify the specific filtration issue to see if you're solving anything.
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Yup, I get all that. I have an automatic water change system set up, so nitrate is not a big concern... I'll just adjust the amount of water changed to keep the nitrates at reasonable levels.

I also agree that the amount of biomedia required for ammonia oxidation is relatively small in most tanks. I am aiming for "overfiltration" so that additional dissolved organic compounds can be absorbed by the biomedia for clearer, healthier. My goal is to have almost no mechanical filtration, but just a ton of bio to see what can be done with just biofiltration.
 
You have confused a fluidised filter with a moving bed bio reactor (MBBR) which is not surprising as many people do and both look similar at first glance.

The fluidised filter encourages young actively growing bacterium by mechanical abrasion of filter media. You will see a distinct colour change in the media zones once established. Sand is mostly used as media but HDPE granules either buoyant or sinking can be.

MBBR is a biofilm filter so you want to encourage established mature complex bacterium that has developed specialised roles. K1 media and numerous variants all which have protected areas to prevent mechanical abraision. MBBR are most effective tumbling so the media can get multiple passes per single pass of water. Another example of biofilm filtration is the dated trickle filter. Unfortunately MBBR work best alone, not in conjunction with other biological filters - anoxic, fluid, etc. And they need air. Don't close them off.

Both very effective if used correctly.
 
Just figured I'd give an update for the handful of you that were interested in this experiment.

The DIY fluidized canister filter/ MBBR thingy cycled in almost exactly one month, and I moved it to the main Mbuna tank 5 weeks ago.

I added a random flow generator in the unit as the intake jet at the top of the filter. I also added a UHMW plate to stiffen up the top. A wavemaker comes on once a day to kick up all the junk into the water column. The fish do a decent job of stirring everything up as well, and I don't have any major poop pockets in the tank.

Parameters have remained rock solid, so it's definitely doing the job of ammonia oxidation. I have effectively 0 mechanical filtration in this setup. Just a very small prefilter sponge to stop the biggest chunks. I don't think the tank is fully settled in still, and I have never gravel vacced any waste, but my water clarity so far is surprisingly... ok for not having any mechanical filtration.



I am able to run the pump at about half speed and still maintain media movement. I try to keep it at or below that for pump life and heat.

I was concerned about the noise, but its a non-issue. the slight clicking of media against glass is very mild once I switched to the RFG nozzle and once the cabinet door is closed, its much more quiet that any air pump I've heard.

Am I convinced it was worth the time and effort? I don't know... not exactly. It's not a like a night and day difference from the mid-size commercial canister it replaced. It's nice to have the extra flow to play with.

Am I convinced that it's the best option for a filter? No... my water still has a slight cloudiness. I'm not totally sure what causing it, but I would like crystal clear water eventually.
  • Is it just cause its a relatively new tank? maybe.
  • Am I overfeeding? Maybe
  • Is there too much natural light from a ton of windows and doors in this corner? Definitely.
Perhaps mechanical and maybe even chemical filtration is still necessary for perfectly clear water, but I'll give this a while longer and see how it goes.

I may also try converting this unit to a non-moving media filter. I could add layers of foam on top of the K1 media. I'd probably use all 20PPI foam in the hopes that I would only have to open up the filter once every 6 months or so. I feel like the constant movement of ALL the media and water doesn't give the detritus any time or place to settle and break down. It has to stay in the water column continuously until it breaks down into smaller and smaller pieces. Maybe this is a good thing? I don't know.

But for now, the fish seem healthy, parameters are great. I'm going to let it continue to establish and see how it goes longer term. I will probably wait till the 6 month mark before I consider any major changes.
 
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