fluidized bed filter
- Thread starter TriMax
- Start date
Runner
Active member
I do not use one, but they have their uses. It is a great filtration method of taking ammonia down to nitrates -- better than a wet-dry with bio-balls, I think. They have a very large surface area for aerobic bacteria and really good insurance against a large fish dying and killing a smaller tank than you have. Many at RC would groan about them not able to break down nitrates like live rock/sand can, though.
macclellan
New member
Yeah, that's true. That's why live rock has replaced bioballs - they only break down NH3 > NO2s > N03, leaving you with the latter. The interior of live rock and deep sand beds contain denitrifying bacteria which break down NO3 to nitrogenous gasses that go to the surface, exiting the aquarium. Nitrates build up for lots of reasons, but mostly because there is too much nitrogenous waste (overfeeding, overstocking, poor maintenance) for the bacteria to process to gas or otherwise be exported from the aquarium (skimmer, refugium, maintenance).
Somebody correct me if any of the above is wrong. That's just my understanding of things.
Somebody correct me if any of the above is wrong. That's just my understanding of things.
EvilMel
is a serious goby fanatic
Joel, I'm not up on the literature or anything BUT it seems to me that if there were bacteria doing the conversion from nitrate into N2 gas that nitrates wouldn't build up.
I mean...it's not like there aren't plenty of other nutrients around. I seriously doubt that nitrogen or anything else is limiting in my dirty tank conditions. There's no ammonia, no nitrite...why would there be nitrates if there were bacteria there to do the conversion to N2? Seems like since the nutrients are there that there would be an explosion of this population of bacteria.
Is that reaction slow (doubtful)? Is it anaerobic (more likely)?
Man...I need to get some time to check this out.
I mean...it's not like there aren't plenty of other nutrients around. I seriously doubt that nitrogen or anything else is limiting in my dirty tank conditions. There's no ammonia, no nitrite...why would there be nitrates if there were bacteria there to do the conversion to N2? Seems like since the nutrients are there that there would be an explosion of this population of bacteria.
Is that reaction slow (doubtful)? Is it anaerobic (more likely)?
Man...I need to get some time to check this out.
macclellan
New member
Yes, anaerobic, which means slow. I still haven't had detectable nitrates in my tank, 9 months and counting. I attribute this to some combination: LOTS of live rock (like 3+ lbs, per gallon), refugium with chaeto, and weekly maintenance (basting of live rock and sand, replacing filter floss, water change).
I thought you'd be all over this stuff with your sciencey background.
I thought you'd be all over this stuff with your sciencey background.
macclellan
New member
Eddie: I'd use the fluidized bed filter on your Oscar tank!!!
Spot on...
Nitrate cycle
http://www.reefkeeping.com/issues/2002-06/dw/index.php
This is why so many people have gone to bacteria dosing as well as vodka and VSV hybrids...
Runner
Active member
The fluidized bed filter is great in a fish-only tank or shark tank or the like because of how quick the large aerobic bacteria surface area on all that sand works to detoxify the ammonia down to nitrates. And fish can handle modest nitrate levels. But it also converts to nitrate faster than live rock can take it all the way to N2 gas. Every surface in the tank has this aerobic bacteria -- which is why nitrates go up unless something like macro algae eats it.
taking it a little futher can anyone tell me what happens if you have bioballs and alot of live rock? I know bioballs break down ammonia to nitrite and then nitrate, and I know live rock does the same and then breaks down nitrate but what if you have both does the nitrate just build quicker?
There is also discussion under advance topics and PaulB's new nitrate thread. Might want to check it out.
Runner
Active member
I have heard it explained on this board that it is a proximity thing -- that the ammonia goes to nitrates on the surface of the rock then moves to the interior of the rock to break down further. And that the bio-balls get to it first and break it down before the live rock can -- thereby preventing the live rock from doing its thing. Personally, though, that all sounds like wild speculation to me. I think it is a lot of hysterical knee-jerk reactions against classical biological filtration such as wet-dry.
On my first saltwater tank, I ran a cannister filter for a while and never noticed nitrates going up any faster than they did in my freshwater tank. And like FW, water changes take care of long-term nitrate build-up. But even with 100+ pounds of live rock and a skimmer (and no cannister or wet dry), I never had 0 nitrates until I introduced macro-algae. So just like in FW, plants are the answer. I had a 135G planted tank with a decent fish load for 5 years that I was bad about not changing the water on. After one 6-month stretch of such laziness, I checked the nitrates and it was 0 (zero, zilch, nada). I started putting tomato fertilizer sticks in the base of my plants and they grew better -- still with 0 nitrates.
My conclusions? I think a skimmer does a lot more for nitrate control than does live rock. And macro is a good complement to the skimmer if used correctly. And if you have large fish in your tank and are not worried about seeking 0 nitrates, there is nothing wrong with a wet/dry (aka bio-balls) or fluidized bed filter as cheap insurance -- but in the planning stages with money not the object I think I'd go with a good skimmer.
Fishboy42
Premium Member
I used a fluidized bed a while-back on an early growout system. They can be great for handling large and fluctuating bioloads because of the huge amount of surface area for bacterial growth and the ability to expose all of that surface to flowing water. They are also self-cleaning in a way, since the media is constantly tumbling. You will want to make sure that the tank has good oxygenation otherwise though, since unlike a trickle filter or bio-wheel that provide gas exchange (off-gassing of CO2 and oxygenation), fluidized beds are net-users of oxygen.
A couple of downsides though: It always seems like a bit of sand is flushed out of the filter and into your tank or sump over time, not much, but it can be kind of annoying
During a power-outage or equipment malfunction, a fluidized bed can die quickly since the highly-aerobic bacteria can quickly use-up all of the available oxygen and expire. Trickle filters and bioballs don't generally experience this since the air provides oxygenation (unless it's a reaaaalllly long outage and the media dries-out).
I gave ours away just because the risk of a loss due to a pump failure or power-outage (pre-generator!) was a bit scary. The biofilters we use now at SA follow a similar principle though-- with floating plastic media tumbled by an array of airstones, still providing a self-cleaning media with high surface area and good exposure to the passing water.
With a good amount of live rock, I don't think you'd need one for your reef, but it would probably be great for an overstocked fishtank.
A couple of downsides though: It always seems like a bit of sand is flushed out of the filter and into your tank or sump over time, not much, but it can be kind of annoying
During a power-outage or equipment malfunction, a fluidized bed can die quickly since the highly-aerobic bacteria can quickly use-up all of the available oxygen and expire. Trickle filters and bioballs don't generally experience this since the air provides oxygenation (unless it's a reaaaalllly long outage and the media dries-out).
I gave ours away just because the risk of a loss due to a pump failure or power-outage (pre-generator!) was a bit scary. The biofilters we use now at SA follow a similar principle though-- with floating plastic media tumbled by an array of airstones, still providing a self-cleaning media with high surface area and good exposure to the passing water.
With a good amount of live rock, I don't think you'd need one for your reef, but it would probably be great for an overstocked fishtank.
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