Carbonate Hardness

[Sparkypn]

What sort of levels of carbonate hardness should I have and are the levels a major concern? Have a 100litre tank with 4 potbelly seahorses

[wasp]

For you, the simplest would be a kh (carbonate hardness) of 7 to 8, same as natural sea water.

People growing corals have it higher than that, to assist calcification in their corals, and coraline algae. However the higher you have kh, the more calcification you will get in the tank, pumps, etc, a lower kh is easier to manage.

If PH is low, it can be raised by increasing kh, however at a kh of 7 or 8 PH can be maintained at acceptable levels by having sufficient aeration.

[Sparkypn]

can the level get to high and does this cause problems to livestock? if so can it be lowered.

[wasp]

It can get too high, but this will only happen if you add too much and overdo it. Anything up to a kh of 12 can be considered "normal" in a tank, but for the sake of the livestock try to avoid sudden big changes.

Due to natural processes, including precipitation with calcium, kh tends to slowly fall. It only goes up if you add some, via a water change, or adding directly a kh raising product such as baking soda.

If seahorses are the only living organism you are keeping, a kh of 7 to 8, and calcium around 380, would be easiest, it will stay fairly constant and could likely be maintained simply by regular water changes.

[ghostface]

For you, the simplest would be a kh (carbonate hardness) of 7 to 8, same as natural sea water.

People growing corals have it higher than that, to assist calcification in their corals, and coraline algae. However the higher you have kh, the more calcification you will get in the tank, pumps, etc, a lower kh is easier to manage.

If PH is low, it can be raised by increasing kh, however at a kh of 7 or 8 PH can be maintained at acceptable levels by having sufficient aeration.

slightly off topic but,

i was reading a thread on zeovit.com where a guy was saying that kh over 8 will retard "skeletogenesis" or calcification in sps. anyone have an opinion on this?

[ghostface]

heres the thread

http://www.zeovit.com/forums/showthread.php?t=6213&highlight=skeletogenesis

[lduncan]

This guy doesn't agree at all. Neither do I. It's not true.

The addition of 2mM bicarbonate to aquaria containing tropical ocean water and branches of Porites porites caused a doubling of the skeletal growth rate of the coral. Nitrate or ammonium addition(20M) to oligotrophic seawater caused a signi?cant reduction in coral growth, but when seawater containing the extra bicarbonate was supplemented with combined nitrogen, no depression of the higher growth rate was evident. We infer that (1) the present dissolved in-organic carbon (DIC) content of the ocean limits coral growth, (2) this limitation is exacerbated by nitrate and ammonium, and (3) adding DIC increases coral calci?catio nrates and confers protection against nutrient enrichment.

Layton

[wasp]

Mesocosms posts in that thread make a lot of sense to me.

I think the other guy was more asking a question, than stating a fact.

[lduncan]

It may make sense, but they were nothing to do with raising alkalinity. The what he was talking was skewing the equilibrium of hydrogen carbonate / carbonate, not increasing the concentrations. The reference he provided does the same. It has nothing to do with increasing alkalinity, it's looking at seeing what happens when you change the partial pressures of atmospheric CO2. Trying to model climate change from the past, and into the future.

Well they asked the question "does bicarbonate addition increase coral growth rates", did a few experiments and answered it. The answer was yes:

This experiment has shown that an addition of sodium bicarbonate causes a dramatic increase in coral calcification. This response is fast and sustained: a significant difference between treatments was established with in the initial growth phase and maintained over the established growth phase. Skeletal growth in corals involves at least two different processes (Barnes and Crossland 1980; Gladfelter 1982). At night, an organic matrix is laid down that deposits the CaCO3 crystal framework, resulting inapical linear extension (Vagoetal. 1997). This process is followed the next day by the nucleation of new crystals into the framework, resulting in increased skeletal density. Hence an increase in skeletal weight could be caused by a higher skeletal density and need not involve an increase in height. However, the linear extension of nubbins growing in enriched DIC was also found to be higher, confirming that both skeletal processes are directly influenced by the supply of DIC. By adding 2mM bicarbonate, we changed not only the total concentration of DIC but also the relative proportion of each carbon species as pH increased from 8.10 to 8.27. While CO2 increased only by a third, HCO3 doubled and CO3 became three times as large. The role of each carbon species in calcification needs to be addressed in future research.

Layton

[wasp]

I think you may have missed the point.

If you read it all properly, you will see that there are a lot of other variables involved. In some conditions increased alkalinity will do what his experiment verified, and in some it won't.

[lduncan]

Actually I think mesocosm has missed the point on this one. While much his information is correct, it doesn't relate to increased alkalinity.

What he is describing is a shift in equilibrium due to other environmental changes, independent of raising alkalinity.

From the paper he references:

Marubini & Atkin-son (1999) showed that a decrease in seawater pH inhibits calcification in Porites compressa, but the conditions tested (pH 8.0 vs pH 7.2 and ?1.81 vs ?0.28) were far more extreme than any real world scenario.

He based his post on this information. Which doesn't directly relate to increasing alkalinity at all.

Layton

[wasp]

There was more to his point than that sentence you quoted

[lduncan]

Elaborate? Anything directly related to increasing alkalinity?

Does this extract make sense?

I emphasized "interact" for a reason ... the pH will strongly influence whether or not skeletogenesis proceeds. We're talking about this chemical equilibrium ...

[HCO3] <---> [H] + [CO3]

For skeletogenesis to happen, we want the equilibrium to shift to the right, i.e., [H] + [CO3]. This is the condition where carbonate can become supersaturated, and precipitate out to form a new bit of coral skeleton.

Skeletogenesis is inhibited as the equilibrium shifts to the left, i.e., [HCO3]. This shift to the left happens as pH drops. As the pH becomes more acidic, the effect is that HCO3 concentration drops. Dropping concentrations are the "opposite" of supersaturated concentrations ... so no skeletogenesis takes place (remembering that there are other variables involved).

Layton

[wasp]

I think the thread is about skeletogenisis and carbonate hardness.

If you cannot see what Mesocosm is talking about ( in it's entire context of course ), there is little point trying to argue with me about it.

Ask Mesocosm. He is a nice guy and will be happy to clarify anything you don't understand. Be warned, he is NOT into arguing though.

[lduncan]

But that's my point. His posts have little to do with what happens when alkalinity is raised.

His posts are talking about what happens when you change other things like pH, lighting and trophic conditions, and the subsequent effects on the carbonate / hydrogen carbonate equilibrium, and then how that effects skeletogenisis.

He did not consider what happens when you change the alkalinity in isolation, which is what you do when adding buffer.

Layton

[wasp]

As I just said, no point arguing with me on it, take it up with him.

He is a nice guy, extremely knowledgeable, and always happy to help.

[lduncan]

The real data is indisputable:

DIC = dissolved inorganic carbon (read as alkalinity)

DIC enrichment was achieved using sodium bicarbonate (ie baking soda, or buffer)

Clearly shows that increasing alkalinity, increases growth rates. In addition, if you increase nitrogen as well as increasing alkalinity the growth rate is also increased.

Another interesting thing this data shows (although unrelated to alkalinity) is that growth rates decrease with the addition of nitrate or ammonium.

Layton

[wasp]

Well I'm not going to argue with your little chart Layton :lol:

I did not see Mesocosm saying anything that would dissagree with it either. What he did was add to the discussion the impact of other variables such as C: N: P ratio, rate of photosynthesis, Ca level, CO3 level, and the "biggies" ... O2 level, pH, and intracellular zooxanthellae density. Other "indirect variables" include photoperiod, temperature, water flow rate(s), and the genetic profile of the specimen.

However, you seem to have an issue with Mesocosm somehow. Once again I would suggest you take it up with him, pointless trying to have an argument with me. I am no expert in this and am therefore happy to accept advice on the subject from people who are. Mesocosm is a qualified scientist and will be happy to answer your questions, provided they are not argumentative.

[lduncan]

I was just posting the info, no need to be patronising. It's not a matter of arguing, its a matter of understanding what you're reading and not being side tracked by "other factors" which have nothing to do with changing alkalinity levels.

It just seems like an attempt by mesocosm to justify the zeo guide recommendations, based on a set of condition which do not occur when you just increase alkalinity.

The info i've seen, and the table above, show that this statement isn't accurate.

Because the oligotrophic-like water column that is generated by the ZEOvit methodology creates an "environmental mix" where dKH beyond the 8-9 level begins to produce concentrations of Ca, O2, and CO3 within coral tissue which are inhibitory with regards to skeletogenesis.

Increasing alkalinity in oligotrophic waters DOES increases growth rate (especially from the dkH levels mentioned above).

Hope that clears it up.

Layton

[wasp]

It just seems like an attempt by mesocosm to justify the zeo guide recommendations, based on a set of condition which do not occur when you just increase alkalinity.Layton

Either you missed the point, or I really don't think you understand. But what would I know? :lol: Little point trying to argue with me about what Mesocosm said.

Once again, your best bet is to ask him, not me. He is a qualified scientist and will be happy to elucidate.

[lduncan]

I don't have questions for him, nor am I asking you questions, nor arguing with you about what he said. Nothing is ambiguous at all.

It's pretty clear. I understand exactly what he is saying. There is another glaring error (most likely typo) in what he wrote too, which you have obviously not picked up. Maybe your the one who doesn't really understand?

You know Eric B has also written on alkalinity levels. IIRC he referenced another study which showed something along the lines of double the alkalinity and you get almost double the growth.

Layton

[wasp]

There is no point telling me that I do not understand, and that I have not picked up Mesocosms supposed error. I am not a scientist nor do I claim to be.

If you feel Mesocosm has got it all wrong, it would be best to talk to him, he is vastly more qualified than you or I.