Sulfide in reef tanks

[Amphiprionocellaris]

Hey everyone!

Let me start by saying that my tanks are running wonderfully and this is not really an "I need advice" thread. Instead, I'm asking for a data dump!

I'm currently working on some theoretical models for nutrient cycling in the reef aquarium (mainly modifying existing models for use in estuaries/coastal ocean), and most of my focus right now is on the fate of sulfur in our tanks. I'm still in the process of parameterizing the model (i.e. setting all the constants etc. so that it's a reliable approximation), but while that's ongoing I wanted to get a sense of the sort of "prevailing wisdom' among the hobby about sulfides in the tank, especially in relation to DSBs. However, that's a broad topic, to say the least, so I thought I would provide a little guidance in the form of some common questions:

1) Under what conditions do sulfides form in our tanks?
2) What does sulfide formation mean for us/what are the dangers?
3) How can sulfide formation be dealt with/prevented?

Feel free to chime in with what you've seen, read about, etc...the more the merrier, because it will likely help guide the types of models/experiments that I run.

Cheers!

 

[bitts]

ok I'm just starting to figure some of this out but interesting info that could help.

relationship between redox & sulfur in the sediment bed.

how redox at x depth may not reflect the amount of O2 present. adding or preventing the development of sulfides.

the change of iron aka ferric iron to ferrous iron & how this relates to sediment color.

how the this change in color relates to the redox potential discontinuity layer.

how bioturbation effects the rate sulfides are released into the water column.

how the pore water can be oxic or sulifdic regardless of the coloration of the surrounding sediment.

these would be some of the things about sulfides in the sand bed that I found to be harder to understand & any input on them could probably help.

 

[Amphiprionocellaris]

Thanks for the input! I'm hoping to put together an article on the subject for a magazine, so I'm going to try and address as many confusion spots as I can. Some quick things I can answer right now, though (went through and edited the quote a little):

1) relationship between redox & sulfur in the sediment bed.

2) the change of iron aka ferric iron to ferrous iron & how this relates to sediment color. how the this change in color relates to the redox potential discontinuity layer.

3) how bioturbation effects the rate sulfides are released into the water column.

1) There's actually something called a redox cascade in the sediment; a vertical (or roughly vertical) progression of which terminal electron acceptor bacteria will use in metabolism (based on the energy gain from thermodynamics). First is oxygen, next is nitrate (via denitrification), then iron oxide, then finally sulfate. 2) That's why levels of iron can control levels of sulfide: sulfate reduction (which produces sulfide) tends only to take place when the previous electron acceptors are depleted. This is a basic rundown of the process, and I will be more detailed if/when an article gets produced (or someone asks for more detail here).

3) is harder to answer because science is still a little fuzzy on how exactly bioturbation affects the sulfur cycle. I know this because I'm working on a PhD paper on exactly that subject! However the general assumption is that bioturbation encourages sediment mixing and increases oxygen penetration depth (decreasing sulfide production), while at the same time increasing burial rate and making more DOM available for use in sulfate reduction (which would increase sulfide production). Which process is more important in the aquarium is something this marine scientist is actively working on.

Hope that clears it up a little...this is something that has been nagging at me since starting the research project!

Cheers!

 

[bitts]

wow thanks I may have more questions for you as I keep reading.