Lava Rock as bio filter media

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nc0gnet0

Discus Breeder
Oct 31, 2009
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Grand Rapids
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Rick
Opps my bad, yes it is feather rock lol and I am a member of koiphen as well.....nice site.....
 
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aquamana5

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May 29, 2013
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I know this thread apparently died a relatively slow death after going off on the paypal tangent for a while, but I'm a new member and would like to make a couple of comments on the lowering of nitrates using lava rock. It actually makes sense if you think of the lava rock as being similar to using live rock in a marine tank. The comparison to bioballs in terms of having greater surface area, although mostly correct, misses an important point. Lava rock, like live rock is larger in size and oftenvery porous, although this varies based on the origin of the rock. Because of the larger size and more total internal area, some of the deepest parts of the rock will often become anaerobic which encourages the growth of the denitifying bacteria which actually converts nitrate into nitrogen gas (search for a typical nitrogen cycle diagram on google if your not familiar with the details). Bioballs do not have this anerobic region, although some of the ceramic media will and can also facilitate denitrification. This is one of the reasons you see less use of this and some of the other types of media in the sumps of marine aquaria than you did when they were first becoming popular. Bioballs, DLS and some of the other media that are used are in fact nitrate factories and the buildup on nitrates is to be expected. Since not all live rock is porous enough and thick enough to counteract this in all cases, you have seen the evolution of deep sand beds, plenums, denitrifying systems (chambers that promote slow flow rates and anaerobic conditions with added nutrients) to enhance the process of denitrification. Breaking lava rock into smaller pieces should in theory actually reduce its effectiveness in denitrification. There are some large black rocks they sell as lava rock in garden centers that will actually float and if put in a tank for a few days will fill with water and sink. These should work very well in a sump or filter and probably have more surface area internally, some aerobic and some anaerobic, than you might imagine.
 
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