Questions about sulfate testing, sulfate overdose, and cloudy kalk

[toaster77]

Fish actually do need K, Ca, Mg - these are important cations for basal cellular functions.

Sulfur is also essential for life. Two of the twenty amino acids have sulfur (methionine and cysteine) and sulfur is present in many other important molecules and proteins in cells. It's importance is underestimated IMO.

Many microbes have the ability to assimilate inorganic sulfate (SO4 -2) and reduce it to sulfide (S -2), which is the biologically active form of sulfur found in molecules and proteins. Most higher eukaryotic species do not have this capability and rely on taking up methionine or cysteine as their sources of sulfur. I presume that sulfate concentrations would fluctuate depending on the population of microorganisms that can reduce it and availability of sulfur-containing amino acids to them.

What I really want to know is the chemical importance of sulfate in seawater, if any. Take a FOWLR tank for example. We already know that K, Ca, and Mg aren't needed by fish. But could you make a salt mix from just NaCl and Na(HCO3)2 with the correct salinity and run a fowlr tank without issue? In other words does the presence of sulfate actually effect the fish in some way? If that's the case then why/how?

None of the results I've seen deviate enough from NSW levels to really answer those sorts of questions.



Possible, but unlikely. I tested it twice with my salifert test kit. It has never failed me before and the color change is very clear.



Nope. I will do that during my water change this weekend and report back with the results.



I would say there is a huge incentive given it's importance to aquariums and fish farms. But I guess that makes some sense.



For me it makes no difference if it is sealed or not after mixing since it quickly builds up a protective CaCO3 layer at the top. Despite the presence of this layer the solution underneath is still cloudy. I have also noticed that this CaCO3 film isn't as thick when using older Kalk. Which seems to support the idea that it is losing potency over time in storage. Something which I must find a way to resolve.



Unfortunately I suspect this may have been the cause of my previously mentioned Ca/Alk issue with the previous tank. I think the small CaCO3 crystals from the cloudy kalk combined with the high PH may have encouraged CaCO3 crystals to grow in the water column and end up actually depleting more Ca/Alk than it replenished. I don't know, what do you think?

I think I should explain a bit about myself at this point so that you can better understand where I'm coming from with these. My main purpose in running reef tanks has been very different from the majority of aquarists. I do it for the science, not appearances. To me it is an excellent tool for better understanding marine biology, chemistry, etc. And as such I am more curious about why certain things happen in a different way for my system than everyone else's (the cloudy kalk for example) and am not necessarily so concerned with the end result.

 

[Randy Holmes-Farley Verified Community Expert]

Fish actually do need K, Ca, Mg - these are important cations for basal cellular functions.

Sulfur is also essential for life. Two of the twenty amino acids have sulfur (methionine and cysteine) and sulfur is present in many other important molecules and proteins in cells. It's importance is underestimated IMO.

Many microbes have the ability to assimilate inorganic sulfate (SO4 -2) and reduce it to sulfide (S -2), which is the biologically active form of sulfur found in molecules and proteins. Most higher eukaryotic species do not have this capability and rely on taking up methionine or cysteine as their sources of sulfur. I presume that sulfate concentrations would fluctuate depending on the population of microorganisms that can reduce it and availability of sulfur-containing amino acids to them.

Actually, sulfate doesn't vary in the oceans, although it can in sediments. It is called a "conservative" ion in that it only varies with salinity. It'as concentration is so high that any uptake that happens does not impact the concentration.

 

[toaster77]

Ok thx for the info I was referring to sulfate concentrations in tanks, which are likely more variable.

 

[Randy Holmes-Farley Verified Community Expert]

Ok thx for the info I was referring to sulfate concentrations in tanks, which are likely more variable.

They certainly are, although I doubt it is from consumption. The salt mixes we use and the additives we put in can skew the chloride to sulfate ratio quite a bit.

FWIW, fish contain only somewhat more sulfur per unit weight than does seawater.