How Deep To Get Denitrification?

[jacksok]

Does anyone know how deep water has to penetrate in live rock before you get denitrification?

The reason I ask is that if we are only talking millimetres then it would make more sense for us to have lots of small bits live rock with a larger surface area, than fewer bigger lumps. But what size of rock would be too small to achieve this denitrifying effect?

Keith

[Glenn@home]

Keith

Ive come to the conclusion that the depth required is not really that deep at all. I think its probalby as much to do with the porosity of the rock in temrs of the size and nature of the pores.

In essence it seems to me that if you can get denitrification taking place in an inch or so of sand then rockwork being much more dense and a fixed structure would likley give rise to denitrifcation at much lower depths.

Even if you considered the inch as a minimum depth, then a pice of rockwork 2" across would likley give rise to denitrifaction. So your contention that smaller bits of lr ir at least rockwork with a fine structure would likely be better than solid lumps of rockwork.

I think perhaps this is where tuffa loses out in the live rock stakes. Other issues aside about holding crap, i susepct that denitrifaction would happily take place, the primary problem is that tuffa is relatively large solid lumps and hence a lower surface area for colonisation of bacteria when compared with tradional lr.

Just a few thoughts

Glenn

[danny]

I believe much the same as Glenn that denitrifaction does not necessarily occur deep with in live rock. My view is that bacteria would form layers of different varieties ie. aerobic on top with anaerobic underneath. Basically this environment would suit the denitrifying bacteria as they would be getting the low oxygen environment and the carbon and nitrate they need direct from the top layer of nitrifying bacteria.
Now this does not mean that multi bacterial films can set up on all surfaces but I assume that the nooks, crannies and capilleries of our live rock would provide a suitable home. To me it does not make sense that nitrate is made in one part of our tanks and then has to diffuse deep into a rock to be converted, that would take too long IMO and wouldn`t cope with the load.
As Glenn says with Tufa I feel that instead of having capilleries, it is more like a unreticulated sponge, and although it is capable of soaking up water it does not offer the internal enviroment that would promote free nutrient exchange.

[jacksok]

Thanks guys, that makes sense.

I've got an old Oase Biotec filter that I'm going to fill with macromedia to create a sort of cryptic zone. I wasn't sure if the media would add much denitrifying capacity to the system or not - sounds like it should :thumbsup:

Keith

[Glenn@home]

Keith

Thining about it dont some of the cannister filter systems contain substrate for denitrification?

I know they generally get slated but it would confirm the concept of using relatively small chunks of rock/meida for denitrification.


Glenn

[jacksok]

Maybe - I thought media like Ehfisubstrat didn't get beyond breaking down ammonia and nitrites. Or are you thinking of some other media?

Keith

[danny]

I reckon it would be more a case of how it is used, for instance you could probably use the same substrate in a wet trickle as a dry trickle with different results.

Also other facters such as whether or not detrivores can get into the media to help clean it of large waste items which may otherwise would be broken down by bacteria only (rot) and water flow would probably influence it`s effectiveness for denitrifying.
Danny

[Glenn@home]

I dont have any brand names in mind, i just thought that some manufacturers claimed that their filtraton systems partially comprised of small bits of substrate would carry out denitrifcation.

Perhaps I had it wrong.

Glenn

[danny]

The makers of these porous sintered glass media do claim denitrifaction Glenn, so you are not mistaken. ;)