Grey patches patch under sandbed

[decentkid]

madmac...no offense here...but i dont really get u...

any i really hope u or blueheaven can answer my question about why black patches are regions of H2S when H2S is colourless...so where does these black patches come from?

[blueheaven]

I am conducting an experiment to find that out. But as it was stated as a form of cyano, I am wondering whether it is dependent on H2S to survive or maybe it is killed by the product of the oxidation of H2S. I'll post results soon.

[madmac]

I'm guessing that cyano won't be destroyed by H2S... they would likely co-exist together quite nicely... I'm sure that wont be same for corals.. whats the purpose of this experiment?... both are things we don't want in our aquaria...

got this quote from a thread i follow :

The question asked was is the hydrogen sulphide I smell when stirring the DSB dangerous in my tank.

My response............

This is a quote from H2S exposure in industry. You can image what your coral and fish experience when exposed to it. if you have H2S in your DSB.....you have neither oxic or anoxic processing going on in the area it is present. It is the odor you smell if you open a sewer pipe full of waste sludge. Men have been quickly over come and died going into holding tanks or sewer lines with H2S. Although I have read the experts say no big deal in a salt water tank because it goes away quickly, I disagree. Also, the presents of H2S is telling you both the oxic and anoxic biological process are not working in the bed.

quote:

Hydrogen sulphide (H2S) itself has an offensive odour of "rotten eggs" at concentrations as low as 50 parts per billion by volume(ppbv) and is toxic at concentrations above 1000 parts per million by volume (ppmv). H2S is a health and safety hazard, and when combined with carbon dioxide (CO2) and water vapour (H2O), corrodes plant equipment such as boilers and piping, and can ruin power-generating equipment. Energy recovery from biogas and other waste streams, a common practice today, is hampered if H2S gas is present. High levels of H2S can also interfere with other processes such as killing useful bacteria in anaerobic digesters. Reducing H2S offers cost savings associated with less maintenance, increased process and energy efficiency, and reduced toxic emissions.

This is the reason why you need positive flow through a DSB to transport waste and food though the bed.

As we all know tank upset are often a chain reaction. H2S exposure may not kill everything, but once it kills a few more sensitive creatures, they die and the tank becomes over loaded, killing more and using up oxygen and finally even toughest creature left go belly up.

You shouldn't use any biological processing system that can easily start that chain reaction.....the conventional sugar sand DSB can easily start the H2S chain reaction of death even with the most attentive husbandry. It is not simply not being oxic or anoxic as it goes bad, is is now producing poision. All you need to do is read what even the "Experts" have experienced themselves when using what is often describe as the ultimate biological reef process, DSB.

[madmac]

madmac...no offense here...but i dont really get u...

any i really hope u or blueheaven can answer my question about why black patches are regions of H2S when H2S is colourless...so where does these black patches come from?

nvm... you'll understand someday...

why the fixation on "black"... I think, it is the chemical by-product of something that is colourless giving out something that is not. Did a google on H2S and this may make sense to you..

http://jamaica.u.arizona.edu/ic/srl/micro/btopic2.html

[butteye]

A pic of the patch ...

Did u use those livesand from the beach?? kinda looked like those rotten SB dugged from our beach....that might contained pollutant chemicals.

My 2cts

[koniyakutz]

Did u use those livesand from the beach?? kinda looked like those rotten SB dugged from our beach....that might contained pollutant chemicals.

My 2cts

Nope, I bought the natural fine sand from a LFS. Was told the sand is collected near the coral reef, dunno how true is that ...

The sand as quite dirty and I spent alot of time washing it with water, also used a magnet to remove the metals.

[Star Polyps]

Looks like Hydrogen Sulphide. Just guessing. Got rotten egg smell?

[blueheaven]

nvm... you'll understand someday...

why the fixation on "black"... I think, it is the chemical by-product of something that is colourless giving out something that is not. Did a google on H2S and this may make sense to you..

http://jamaica.u.arizona.edu/ic/srl/micro/btopic2.html

I am trying to find out the origin of the black substance. It could well be anything from a ppt to lifeforms.

[madmac]

is your question is where does black colour come from OR where does H2S come from?

black because it a chemical property of H2S reactions/ppt (precipitation?)

I think this could be a layman explanation :

http://www.ocean.udel.edu/blacksea/chemistry/chemistry.html

Bacteria enhance the decomposition process, but they need certain chemicals in order to do their thing. In the sediments and water column of the Black Sea, bacteria first use oxygen (O2), which is converted to water (H2O) during the break down of microscopic plants (phytoplankton) and microscopic animals (zooplankton).

After the oxygen is depleted, the bacteria use other natural oxidants in a stepwise progression based on decreased energy yield from the reactions. These natural oxidants are nitrate (NO3-), manganese dioxide (MnO2), iron oxides (e.g., FeOOH), and sulfate (SO4 2-), which are reduced to ammonia (NH3), dissolved manganese (Mn2+), iron (Fe2+), and hydrogen sulfide (H2S), respectively......  The release of hydrogen sulfide (H2S) — a toxin to fish and crustaceans — indicates nutrient overenrichment (eutrophication) and water column stratification.

IOW : sulfate compounds (oxidants) can/will be used as an oxygen source for anaerobic decomposition of organics giving H2S

....

This process of decomposition is what SBs do in nature and in your tanks they do no different.... they will produce H2S... its a question of time. dk you got it the other way round if you think you can prevent H2S by employing critters to stir the SB... critters/animals can't prevent H2S formation, they could prevent the spread.

[blueheaven]

Ok chemical analysis of black substance will be out next wed so let's be patient

[decentkid]

is your question is where does black colour come from OR where does H2S come from?

black because it a chemical property of H2S reactions/ppt (precipitation?)

I think this could be a layman explanation :

http://www.ocean.udel.edu/blacksea/chemistry/chemistry.html

IOW : sulfate compounds (oxidants) can/will be used as an oxygen source for anaerobic decomposition of organics giving H2S

....

This process of decomposition is what SBs do in nature and in your tanks they do no different.... they will produce H2S... its a question of time. dk you got it the other way round if you think you can prevent H2S by employing critters to stir the SB... critters/animals can't prevent H2S formation, they could prevent the spread.

hmmm....bro...thanks for that...kind of cleared my doubts....

also i didnt think bacteria using oxygen from sulfate compunds...thats a very good point...

btw...i think its the way i type...i was tyring to say that critters can prevent the build up of hydrogen sulphide

[blueheaven]

Sorry guys but the anlysis results will only be released next week as there has been some slight delay. Anyway, what detrimental effects do H2S have on our tanks?

[madmac]

Definately hydrogen sulphide

Its a poisonous substance but usually it would not accumulate to fatal concentrations in our tanks. Just get you sandbed oxygen rich water and it'll go away

huh? ... will the real blueheaven pls stand up?

=======

The sulfide tolerance of milkfish and tilapia in relation to fish kills in farms and natural waters in the Philippines. Bagarinao, T.; Lantin-Olaguer, I. SEAFDEC Aquaculture Department, Iloilo, Philippines. Hydrobiologia (1998), 382 137-150. CODEN: HYDRB8 ISSN: 0018-8158.

Abstract

Fish kills of milkfish Chanos chanos and tilapia Oreochromis spp. now occur frequently in brackish, marine, and freshwater farms (ponds, pens, and cages) in the Philippines. Aquafarms with high org. load, limited water exchange and circulation, no aeration, and high stocking and feeding rates can become oxygen-depleted and allow sulfide from the sediments to appear in the water column and poison free-swimming fish. The sulfide tolerance of 2-5 g milkfish and 5-8 g O. mossambicus was detd. in 25-L aquaria with flow-through sea water (100 mL min-1) at 26-30° and sulfide stock solns. pumped in at 1 mL min-1. Total sulfide concns. in the aquaria were measured by the methylene blue method and used in the regression against the probits of % survival. Four expts. showed that the two species have similar sulfide tolerance. In sea water of pH 8-8.5, about 163±68 mM or 5.2±2.2 mg l-1 total sulfide (mean ± 2 se) or 10 mM or 313 mg l-1 H2S was lethal to 50% of the fish in 4-8 h, and 61±3 mM total sulfide or 4 mM H2S in 24-96 h (to convert all sulfide concns.: 1 mM = 32 mg l-1). Earthen pond bottoms had 0-382 mM total dissolved sulfide (mean ± sd = 54±79 mM, n = 76); a tenth of the samples had >200 mM. The water column may have such sulfide levels under hypoxic or anoxic conditions. To simulate some of the conditions during fish kills, 5-12 g milkfish were exposed to an abrupt increase in sulfide, alone or in combination with progressive respiratory hypoxia and decreasing pH. The tests were done in the same flow-through set-up but with sulfide pumped in at 25 mL min-1. The lethal concn. for 50% of the fish was 197 mM total sulfide or 12 mM H2S at 2 h, but 28-53 mM sulfide allowed fish to survive 6-10 h. Milkfish in aquaria with no aeration nor flow-through sea water died of respiratory hypoxia in 5-8 h when oxygen dropped from 6 to 1 mg l-1. Under respiratory hypoxia with 30-115 mM sulfide, the fish died in 2.5-4 h. Tests with low pH were done by pumping a weak sulfuric acid soln.

at 25 mL min-1 into aquaria with flow-through sea water such that the pH dropped from 8 to 4 in 5 h. Under these conditions, milkfish died in 7-9 h when the pH was 3.5. When 30-93 mM sulfide was pumped in with the acid, the fish died in 2-6 h when the pH was still 4.5-6.3. Thus, sulfide, hypoxia, and low pH are each toxic to milkfish at particular levels and aggravate each other's toxicity. Aquafarms must be well oxygenated to prevent sulfide toxicity and fish kills.

[blueheaven]

huh? ... will the real blueheaven pls stand up?

It will usually not accumulate to fatal concentrations

[Alentino]

Dr Ron Shimek has already cleared this myth of Hydrogen Sulfide gas poisoning in tanks. He said that Hydrogen Sulfide will indeed form in the lowermost layer of a deep sand bed. But It will NOT migrate upwards through the sand to poison your tank. It does'nt work that way. There has been no evidences that Hydrogen Sulfide may reach toxic levels in a normal well maintained tank . There's no need to worry about those black patches, just leave them be.

[madmac]

As H2S mixes with air, it reacts with O2 to form sulphate, this flux goes like this.. .it moves up thru' the SB, turns to sulphate, the anoxic/anaerobic uses it again to form H2S, so it goes down again and becomes H2S... Thats what happens in a SB with... it is very situational... it can happen in weeks or in years, but it happens(otherwise how does it come out in the first place), it will burp out as a gas and your water flow bring it all over to every corner of your tank.. corals(most of the sensitive ones) will slowly deteriorate in health...

As it leaks thru the SB, it will kill organisms and bacteria along the way, hence it spreads... because it is toxic, H2S tolerant critters will avoid the going near there, 1. no food, 2. dangerous to their lives.

No evidences! what evidence do you want/need? When there is poison in your home, when there is a gas leak... do you say, it is ok, just leave the windows open, the in-coming air will dilute it... jus leave them be, dont' worry about it...

disclaimer: father of 4 young kids, lover of sea-life, and hater poisons lying around doing nothing useful.

[Alentino]

I'll try to explain to the best of my knowledge,

Good point, but Hydrogen sulphide will only move to shallower oxygenated portion of the sand in trace amounts as water flow slowly through the sand bed, but does'nt leaked out as toxic gas. When that happens, like what you said it will get converted to Sulfate, but sulfate ends up getting incorporated into organism and bacterial biomass at the sediment surface. It ends here.

Hydrogen sulphide will remain only in the black patches deep in the sediment layer. If you don't poke somethin in to stir it up it should'nt escape into the top water column. Has anyone here seen the black patches moving up through the sand by itself and burping out bubbles at the surface layer?

I presume you're a fan of bare-bottoms madmac. It is true that bare-bottoms have their valid points of practical use too if coupled with maintainence like detritus siphoning and stuffs. The same holds true for DSB; proper management of this natural filtration component will lead the hobbyist to the same results, a successful poor nutruent reef tank.

If anyone wants to know the proper management technique of DSB, just read Blueheaven's article, follow the points and you should'nt go wrong.

[madmac]

What peeves me is the confusion that this thread is turning out to become... it is firstly a thread about H2S, lets not turn this into one that is BB or DSB.

We've established tt H2S is toxic. Yet... there are qs that play it down... like saying, "You know this is poison, but it wont kill you, if you don't get enough of it"... So is it poison or not. Facts can't be myths... In chemistry, it is very exacting. We share in one common love about reef-keeping. I'm a believer of anything that works(simplicity is key to me), within the constrains that I've set for myself... As we progress, so does the knowledge pool in the reef-keeping world... tech and understanding increases and you could embrace it or say no... but pls, if you are unsure... don't confuse others here with the playing of words.

.... but Hydrogen sulphide will only move to shallower oxygenated portion of the sand in trace amounts as water flow slowly through the sand bed.

Point 1. Explain how H2S gets there in the first place, before it moves to shallow points

but does'nt leaked out as toxic gas.

yes it does/will... go do your own research... your nose will tell you when that happens.

When that happens,

See this is how you confuse... are you saying it will or it won't?

like what you said it will get converted to Sulfate, but sulfate ends up getting incorporated into organism and bacterial biomass at the sediment surface. It ends here.

see point 1. If you've maintain it so well... how does it get there in the first place....

What you hv as confirmed by Dr. Ron is H2S in the bottom of the SB.. You are taking a systematic risk by keeping it there. ..you know this, you are required to act otherwise you remain negligent

[blueheaven]

I personally believe that H2S will leak out but its not enough to adversely affect our tank inhabitants. In fact, you see all those poisons that corals produce, you will think twice about H2S. You can smell it, yes, but you know its critical when it makes you drowsy. And like what Alentino said, proper set up sandbeds do not have any trace of the "black stuff".

Anyway, analysis results coming soon.

[koniyakutz]

Hi guys, this is how my sandbed looks after increasing water flow in my tank.

The black patch is gone and algae is starting to grow on the front glass. In fact, I can now see alot of tiny air bubbles and 'tunnels' in the sandbed.

[blueheaven]

My advice, use a black stip of paper to cover the exposed area (outside)

You want to prevent algae growths in the sand