Jump to content
SaltCritters.com

Does coral covering rock limit live rock filtration ability?


duganderson

Recommended Posts

I'm curious if you have a lot of coral covering your live rock, especially encrusting corals (such has my encrusting gregorian), does it limit the ability of the live rock to provide it's biological filtration ability since much of the surface area (especially the sides exposed to light) might be covered???

 

Thanks!

Link to comment

Yes, it would actually decrease the filtration capability by decreasing the amount diffusion to and from the rock. It is still able to do some filtering and the corals themselves actually do some, as well, so I wouldn't let it concern you too much. The same applies to those who have seagrass in sandbeds--organic debris from the leaves, if allowed to pile up, would eventually smother many infauna. Some are more tolerant than others, but it just depends on the organism.

Link to comment

Make sure you have good flow behind and under your rocks. You will be fine assuming you arent going crazy with your bio load. The amount of bacteria is limited based on the available food supply. With a good setup that allows maximum circulation, you will be good.

Link to comment

Believe it or not it actually helps with the conversion of NO3 to N2. The bacteria that consume nitrate as food are anerobic so by decreasing the rate of diffusion of oxygen rich water into the rock the closer to the surface of the rock the anerobic bacteria can survive. Thus, more internal volume of the LR can support denitrification.

 

Additionally, coral isn't waterproof and the reason many people will say it decreases the ability of live rock to support denitrification is the bioload increase as the corals grow and spread.

Link to comment

Really interesting. Thanks for that insight Salty. I've wondered about this for a while as well and thought it might be a culprit in "old tank syndrome".

Link to comment

Thanks for the response.

 

Does coral really increase the bio load much? How does it create bio load? Do certain types of corals increase bio load more (softies, LPS, SPS, anemones, etc.)?

Link to comment

Well any coral you feed will for sure. An anemone is a massive eater if you feed it. My duncan coral has 40 heads so feeding each one of those can produce some waste. Just be smart with feedings.

Link to comment
Believe it or not it actually helps with the conversion of NO3 to N2. The bacteria that consume nitrate as food are anerobic so by decreasing the rate of diffusion of oxygen rich water into the rock the closer to the surface of the rock the anerobic bacteria can survive. Thus, more internal volume of the LR can support denitrification.

 

Additionally, coral isn't waterproof and the reason many people will say it decreases the ability of live rock to support denitrification is the bioload increase as the corals grow and spread.

 

Over time, this would become limited, as well. It would eventually start decreasing the amount of NO3 physically diffusing into the rock structure and limiting denitrification, assuming extensive (or complete) coverage. Not only would rock-dwelling bacteria have to compete with a tissue barrier, they'd also have to compete with the nitrogen uptake of the corals themselves.

 

Of course, there will be bacteria just about anywhere, so maximizing the number of areas that all of this can still occur is very easy and probably never an issue. This is especially true of those systems that have sand beds.

Link to comment

it sounds like everyone is just speculating imo

 

there's no way these guys could know this for a fact

 

link to a scientific journal or it didnt happen imo

 

 

 

best way to tell for a hobbyist is with first hand expirence--but that's probably going to be hard to find.

 

I would think that the tank would adjust it's own biological filtration abilities to cope with however the corals are affecting it. coral grows at a slow enough rate that the bacterial colonies would be able to adjust their population size/positions accordingly

 

that's my scientific .02 like everyone else :P

Link to comment

I'm a research chemist by profession with experience with diffusion and consumption of reagents in highly porous media. What I can tell you without a doubt is the flow of water into the live rock is not needed for denitrification to occur. As nitrate is consumed by bacteria inside the rock a concentration gradient is formed which causes diffusion of nitrate into the depleted region without the need for solvent mass transport, in this case water.

 

The reason anerobic bacteria will not reside in the outermost inch or two of LR is because there is to much dissolved oxygen available and aerobic bacteria thrive. The same can be said about deep sand beds.

 

What suprises most people is the massive amount of oxygen that is dissolved in well aerated water. Think about the flow of water 2 or 3 inches down in a sand bed. It's tiny at best but still contains enough oxygen to support aerobic bacteria. So basically there are only two ways to create a larger detritrificaion "zone" in LR. Either reduce the amount of dissolved oxygen in the water (not a good idea) or decrease the flow of oxygenated water into the LR which is exactly what something like coral will do.

Link to comment
I'm a research chemist by profession with experience with diffusion and consumption of reagents in highly porous media. What I can tell you without a doubt is the flow of water into the live rock is not needed for denitrification to occur. As nitrate is consumed by bacteria inside the rock a concentration gradient is formed which causes diffusion of nitrate into the depleted region without the need for solvent mass transport, in this case water.

 

The reason anerobic bacteria will not reside in the outermost inch or two of LR is because there is to much dissolved oxygen available and aerobic bacteria thrive. The same can be said about deep sand beds.

 

What suprises most people is the massive amount of oxygen that is dissolved in well aerated water. Think about the flow of water 2 or 3 inches down in a sand bed. It's tiny at best but still contains enough oxygen to support aerobic bacteria. So basically there are only two ways to create a larger detritrificaion "zone" in LR. Either reduce the amount of dissolved oxygen in the water (not a good idea) or decrease the flow of oxygenated water into the LR which is exactly what something like coral will do.

 

I never meant to imply that there would be no diffusion of nitrogen. I guess what I'm questioning is whether or not it would be as effective to the system as a whole in such a situation and whether it would reach the bacteria at significant rates (and even affect bactial populations). I know porewater studies often show high dependence upon advection, which is why I came to the conclusion I did. The same applies to many bioturbation studies.

Link to comment

Yes, it does seem a bit of a stretch to say that depletion due to anaerobic activity would cause a concentration gradient through the tissue/skeleton of a coral. Also, those bacteria would have to compete with the corals' zooxanthellae for the nitrate.

Link to comment

Archived

This topic is now archived and is closed to further replies.

  • Recommended Discussions

×
×
  • Create New...