There are dead spots and dead spots.

[atoll]

Seen a few posts on other threads about reefscape and so called dead spots. Consensus of opinion seems to be they are a bad thing. However, although my reefscape are built off the sand I have never experienced issues with dead spots, no hydrogen sulfide for instance.

This got me thinking there must be dead spots on the reef after all arent most reefs built off the sand or deep down off many years of dead coral. Of course there is a lot more water to dilute things like hydrogen sulfide but does it exist in any quantity on the reef.

With my tank none of my rock, which is built off the sand, have flat bottoms so worms can still get under 90% plus of it I would imagine, I can't obviously measure that but makes sense to me.

I am not saying people here haven't had issues with hydrogen sulfide build up just that in all my years with many reef tanks I have never experienced such a problem.

OK so my sand is only 1.2"to 2" thick but my rock is still sitting on it with some probably on the glass bottom. Do I have detritus in my sand etc, hell yes of course, is it a problem, no not at all. I don't have any prefiltration at all. No filter wool, no roller mat and no filter wool. I do give the sand a blast from time to time but that's it.

 

[Isopod80]

I haven't had a problem with dead spots either but the ocean has much greater flow and more diversity in the sandbed. In a reef tank is guess it really depends on the size of the spots and maintenance.

 

[atoll]

I haven't had a problem with dead spots either but the ocean has much greater flow and more diversity in the sandbed. In a reef tank is guess it really depends on the size of the spots and maintenance.

Not a the reef has high flow in fact I would wager some reefs have very little flow hence why certain corals in our tanks prefer slow flow. As for diversity well possibly but we have all manner of worms and pods in our sand and under our rocks. No maintenance under my rocks either.

 

[Timfish]

I don't really understand this attempt to avoid all dead spots myself. For one, in the 30+ years I've been keeping reef systems and 20+ years I've had my maintenance business I've never seen a system that didn't have dead spots, between variations in aquascaping and currents cancelling themselves out it's going to happen. The more I learn about reefs and the importance of the diverse microbial and macro porcesses there's important biology that needs minimal flow and pH gradients to help dissolution of carbonate substrates I don't worry about the "dead spots". Lastly, there's Nikko Reef, one of the most pristine reefs and so isolated it takes 100 days for water exchanges with the open ocean.

 

[fish farmer]

Seen a few posts on other threads about reefscape and so called dead spots. Consensus of opinion seems to be they are a bad thing. However, although my reefscape are built off the sand I have never experienced issues with dead spots, no hydrogen sulfide for instance.

This got me thinking there must be dead spots on the reef after all arent most reefs built off the sand or deep down off many years of dead coral. Of course there is a lot more water to dilute things like hydrogen sulfide but does it exist in any quantity on the reef.

With my tank none of my rock, which is built off the sand, have flat bottoms so worms can still get under 90% plus of it I would imagine, I can't obviously measure that but makes sense to me.

I am not saying people here haven't had issues with hydrogen sulfide build up just that in all my years with many reef tanks I have never experienced such a problem.

OK so my sand is only 1.2"to 2" thick but my rock is still sitting on it with some probably on the glass bottom. Do I have detritus in my sand etc, hell yes of course, is it a problem, no not at all. I don't have any prefiltration at all. No filter wool, no roller mat and no filter wool. I do give the sand a blast from time to time but that's it.

This past winter I pulled apart a 120 gallon tank that had a 20 year old 4 inch oolitic sandbed. This was in a FOWLR tank, I had lots of detritus buildup the last few years and was starting to siphon the top layers.

I expected a nasty low tide mess when I pulled the bed....nothing black, not a whole bunch of detritus down deep. It smelled fine. I could have rinsed the sand and used it again

 

[Hans-Werner]

Dead spots in general are quite harmless, since, even when substrate gets black and hydrogen sulfide is produced by bacteria, there are other bacteria in the transition zone from anoxic to oxic conditions, that make use of exactly this hydrogen sulfide to gain energy from and to oxidize it back to sulfate or sulfur.

Some of these bacteria even may get visible. if you introduce live rock into a tank and there are decaying sponges on it you may notice the growth of white, mold-like spots. These spots are sulfur bacteria of the genus Beggiatoa that oxidze hydrogen sulfide to tiny sulfur particles which give the bacteria the white color.

In this way under normal conditions no hydrogen sulfide gets into the free water.

 

[atoll]

Dead spots in general are quite harmless, since, even when substrate gets black and hydrogen sulfide is produced by bacteria, there are other bacteria in the transition zone from anoxic to oxic conditions, that make use of exactly this hydrogen sulfide to gain energy from and to oxidize it back to sulfate or sulfur.

Some of these bacteria even may get visible. if you introduce live rock into a tank and there are decaying sponges on it you may notice the growth of white, mold-like spots. These spots are sulfur bacteria of the genus Beggiatoa that oxidze hydrogen sulfide to tiny sulfur particles which give the bacteria the white color.

In this way under normal conditions no hydrogen sulfide gets into the free water.

That's interesting and confirms my belief there is no issue with dead spots which in effect is a poor name as these areas as far from dead.

 

[ZoWhat]