The Truth About Bio-Balls

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Monster Tank Builder
May 29, 2007
New Orleans, LA
By the way, your referring to "anaerobic" bacteria is not really correct - our good nitrate "eating" bacteria needs some oxygen in the water.
Sorry, you're wrong.

The absence of oxygen is indicated as anoxic; and anaerobic is used to indicate the absence of any electron acceptor (nitrate, sulfate or oxygen)

Denitrification takes place under special conditions in both terrestrial and marine ecosystems. In general, it occurs when oxygen (which is a more favourable electron acceptor) is depleted, and bacteria turn to nitrate in order to respire organic matter. Because our atmosphere is rich with oxygen, denitrification only takes place in some soils and groundwater, wetlands, poorly ventilated corners of the ocean, and in seafloor sediments.

The good nitrate eating bacteria does not live where oxygen is not depleted.


AC Members
Jul 13, 2007
Kind of off the subject; but this whole issue is much more important in a Reef than in a FOWLR tank. I know the lower the nitrates, the better. But; there seem to be many hobbiests with FOWLR tank obsessed with getting nitrates down to zero. Unless there is some new evidence, I believe a reading of, say 20ppm, is perfectly for fish. NOT inverts. I would use an even higher number, and can quote sources; but 20ppm is a reasonably attainable and safe number for FOWLR tanks. (Another mis-conception, IMO, is that carnivores produce more waste than herbivores--but I'll save that for another rant.) I just noticed that the Aquaria Central menu says this is the fish-only forum; so I guess my initial rant is relevant
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AC Members
Jul 3, 2007
San Luis Obispo
Have you ever removed a piece of LR from the water and noticed the water draining out of the interior of the rock? Good quality live rock is VERY porous, and if a small piece of LR rubble is placed in strong flowing water (such as in most sumps) the interior just won't become anoxic enough for the nitrate reducing bacteria to live (multiply) in (in meaningful quantity), so the small piece of rubble will have just as little anoxic bacteria living inside it's "deep" pores as the bio balls or hair curlers will have living on their outer surface.

No, not really...

Please understand the principle I'm trying to get across - it's irrelevant what the substrate is made of (rock or plastic...), the only important criteria needed for nitrate reduction are the size of the surface area and an optimally anoxic condition in the water and/or substrate (and of course a supply of food - nitrate). By the way, your referring to "anaerobic" bacteria is not really correct - our good nitrate "eating" bacteria needs some oxygen in the water. Proper anaerobic bacteria use sulpher instead of oxygen to "eat" the nitrate, and this results in the dreaded hydrogen sulphate black areas one ofter find deep inside really large pieces of LR (or sometimes in really deep sand beds).
Like nolapete said, the oxygen has to be depleted... And sure, if you crack open a piece of LR, sure, water may drain through it... Water must be present obviously correct? In the case of LRR, sure the rock is porous and water is within even the smallest crevices, but consider the amount of flow through these areas... It is unmeasureable... This is where denitrification takes place..

This unmeasureable flow through the cracks allows time for the oxygen to get depleted by the time it reaches the denitrifiying bacteria that will eliminate the nitrates...

There is no way that one can have the nitrate reducing bacteria anywhere where there is decent flow with a media such as bio-balls or hair curlers... There is always going to be water flowing (thus even a small amount of oxygen) reaching these areas not allowing denitrification to take place.. (ie nitrates to atmospheric nitrogen)

New Reefer, im sorry, you should do some homework on this subject...