Optimal Parameters for a Coral Reef Aquarium: By Randy Holmes-Farley

[pwilliaml]

No. pH always between 8.2 and 8.3. Vinegar is spaced out to 20ml 6 times a day.

Interesting, you'd think pH would take a hit with the addition of an acid. Do you do anything to help raise pH in general?

 

[Randy Holmes-Farley]

Interesting, you'd think pH would take a hit with the addition of an acid. Do you do anything to help raise pH in general?

All types of carbon dosing have a temporary pH lowering effect since they end up as CO2. Vinegar just has more of it up front than, say, vodka.

If you spread it out enough, the effect is very minor as the tank has a chance to blow off any excess CO2.

If dosing vinegar all at once, there will be a substantial pH lowering effect. When I was dosing that way, i saturated the vinegar with calcium hydroxide to prevent there being any pH lowering. That is cheap and easy.

I later switched to a dosing pump to spread out the dosing more, and dropped using the calcium hydroxide.

 

[Bill Urbanski]

Interesting, you'd think pH would take a hit with the addition of an acid. Do you do anything to help raise pH in general?

Nope. Just keep the window next to the tank open.

 

[AirIck]

@Randy Holmes-Farley How do I know if I am ready to start dosing or not? I am able to stay within the recommended parameter ranges of Alk, Cal, and Mag with my weekly water changes. However, I do swing from the upper end of the parameters to the very bottom of the parameters by the time I am ready for a water change. Am I good to continue to monitor with water changes only or would it be wise to start slowly dosing so I am not going from upper to lower ends of the ranges, particularly my Alk?

My Alk starts around 9.7 after water change and then by the end of the week I'm around 9, my Cal I'm more consistent (tend to run higher for some reason right after a water change, about 460 then starts to drop throughout the week). Mag, after water change I'm about 1350, by end of week up in the upper 1290s. I only test with my Apex (no backup test although I do own a Hanna Alk tester and redsea Cal and Mag test kits).

I hope my question made sense!

 

[Randy Holmes-Farley]

If water changes alone keep alk in a range that is ok for you, there's no need for dosing.

As soon as alk drops more than you want, then dosing is in order.

Calcium drops much more slowly, and I'd use alk as the guide for dosing both.

 

[ISpeakForTheSeas]

Hey Randy, first off, great article.

Second, are these surface water values fairly uniform to a substantial depth, or do they change dramatically within just a few dozen meters? (I.e. is the value at the surface the same or close to the same as at 30 meters deep? 60 meters?)

Third, by chance, do we know what these parameters’ values typically are for deeper points in the ocean, or just for the surface? (In other words, do we know what these parameters typically are for the mesopelagic, bathypelagic, abyssopelagic, and hadopelagic zones, or just for the epipelagic zone?)

Fourth (and last), do you have any recommendations on where/how to learn more about these values and the role they play in fish/corals/etc., particularly in the deeper parts of the ocean?

 

[LeBon]

In days gone by, most of these parametres were kept in balance with simple water changes and top offs.

Nowadays the majority of folk are removing all the trace elements with rodi systems and not replacing them during top off. Making more regular regular waterchanges more import than ever so at least we are adding what is in the salts.

I dont think the majority of 'hometanks' really still need anything more than these waterchanges/trace replacements. Its pretty large tanks'packed' with stoneys that may well need calcium reactors etc

 

[Randy Holmes-Farley]

Hey Randy, first off, great article.

Second, are these surface water values fairly uniform to a substantial depth, or do they change dramatically within just a few dozen meters? (I.e. is the value at the surface the same or close to the same as at 30 meters deep? 60 meters?)

Third, by chance, do we know what these parameters’ values typically are for deeper points in the ocean, or just for the surface? (In other words, do we know what these parameters typically are for the mesopelagic, bathypelagic, abyssopelagic, and hadopelagic zones, or just for the epipelagic zone?)

Fourth (and last), do you have any recommendations on where/how to learn more about these values and the role they play in fish/corals/etc., particularly in the deeper parts of the ocean?

Which parameters are you referring to?

Alkalinity and the major ions (and many minor ions) of seawater only vary by local salinity, not location or depth (unless you are near a river mouth).

Trace elements vary mostly by depth, with different ones enriched or depleted at different depths. Some, like iron, are depleted at the surface, some at lower depths.

The book "Chemical Oceanography" by Millero shows lots of this sort of data and discusses it in detail.

 

[ISpeakForTheSeas]

Which parameters are you referring to?

Alkalinity and the major ions (and many minor ions) of seawater only vary by local salinity, not location or depth (unless you are near a river mouth).

Trace elements vary mostly by depth, with different ones enriched or depleted at different depths. Some, like iron, are depleted at the surface, some at lower depths.

The book "Chemical Oceanography" by Millero shows lots of this sort of data and discusses it in detail.

I was wondering primarily about Calcium, Magnesium, Phosphate, Ammonia, the parameters in Table 2 (Potassium, Silica, Iodine, Nitrate, Nitrite, Strontium, ORP, Boron, and Iron), and any other values that might be important at lower depths but not near the surface.

I know that Nitrate and Phosphate increase drastically from the surface of the ocean to the top of the mesopelagic zone, but I'm hoping to learn more about the roles, concentrations, and importance of Nitrate, Phosphate, and anything else that might be important at various depths/zones in the ocean as well.

Thank you for the recommendation! The book looks like it will be a great resource for me to learn from/start with.

 

[Randy Holmes-Farley]

I was wondering primarily about Calcium, Magnesium, Phosphate, Ammonia, the parameters in Table 2 (Potassium, Silica, Iodine, Nitrate, Nitrite, Strontium, ORP, Boron, and Iron), and any other values that might be important at lower depths but not near the surface.

I know that Nitrate and Phosphate increase drastically from the surface of the ocean to the top of the mesopelagic zone, but I'm hoping to learn more about the roles, concentrations, and importance of Nitrate, Phosphate, and anything else that might be important at various depths/zones in the ocean as well.

Thank you for the recommendation! The book looks like it will be a great resource for me to learn from/start with.

Of your list, these only change with salinity:

Calcium, Magnesium, Potassium, Iodine, Strontium, Boron.

The articles I show at the top of this forum on the individual ions often have additional discussion on the others.

For example:

Chemistry And The Aquarium: Iron In A Reef Tank

Randy discusses iron and its usage in our aquariums.

reefs.com

Iron in the Ocean
Iron in the ocean is primarily iron(III) (Fe3+), because any Fe2+ that forms is oxidized back to Fe3+ by oxygen (O2) and other oxidizing species. The concentration of iron varies substantially with location and depth, and is depleted at the surface due to scavenging by organisms. Typical surface concentrations are on the order of 0.1 nM (0.000006 ppm). When not bound to an organic molecule, iron in seawater exists primarily as dissolved Fe(OH)3. Iron(III) is quite insoluble in seawater at pH 8.2 due to the formation of iron oxides (rust) of various compositions. In fact, it is one of the least soluble cations in seawater. So dumping in a lot of unbound iron into a reef tank may simply result in much of it precipitating onto the bottom.

In most of the oceans, the growth of phytoplankton is limited by nitrogen sources (typically nitrate). In some places, however, where there is adequate nitrogen, phosphorus, and silica (if we are referring to diatoms), the growth of phytoplankton is believed to be limited by the availability of iron. Experiments have, in fact, shown that growth can be increased in some of these areas through addition of iron to the ocean. Many of these experiments are summarized by Frank Millero in his book “Chemical Oceanography” (second edition; 1996).

One of the facts that arises from these studies involves phosphorus. The preferred solution ratio of iron to phosphorus is between 1:100 and 1:1250 for coastal species of phytoplankton, and about 1:10,000 for open ocean species, suggesting that the open ocean species have developed better mechanisms for collecting and/or using iron. I mention this fact not because we can use it quantitatively to know if we have enough iron in our systems, but rather to demonstrate that different organisms have different abilities to fulfill their iron requirements, and that iron may be limiting the growth of one organism, while in the same tank, nitrogen, phosphorus or silica may be limiting to another.

Note that I stated that if the iron is not bound to an organic it would primarily exist as soluble Fe(OH)3. However, in both the oceans and in reef tanks, there are uncounted hordes of organic molecules that bind iron quite strongly. Unfortunately, while the speciation of some metals has been well studied in some fresh water systems (such as copper in certain lakes), the speciation of iron in seawater has not generally been elucidated. I expect this lack of information stems largely from the difficulty in identifying all of the organic species present, in knowing which ones are binding iron, and in the fact that the nature of organic molecules in seawater will vary from location to location, from season to season, and likely even with the time of day.

 

[ISpeakForTheSeas]

Of your list, these only change with salinity:

Calcium, Magnesium, Potassium, Iodine, Strontium, Boron.

The articles I show at the top of this forum on the individual ions often have additional discussion on the others.

For example:

Chemistry And The Aquarium: Iron In A Reef Tank

Randy discusses iron and its usage in our aquariums.

reefs.com

Iron in the Ocean
Iron in the ocean is primarily iron(III) (Fe3+), because any Fe2+ that forms is oxidized back to Fe3+ by oxygen (O2) and other oxidizing species. The concentration of iron varies substantially with location and depth, and is depleted at the surface due to scavenging by organisms. Typical surface concentrations are on the order of 0.1 nM (0.000006 ppm). When not bound to an organic molecule, iron in seawater exists primarily as dissolved Fe(OH)3. Iron(III) is quite insoluble in seawater at pH 8.2 due to the formation of iron oxides (rust) of various compositions. In fact, it is one of the least soluble cations in seawater. So dumping in a lot of unbound iron into a reef tank may simply result in much of it precipitating onto the bottom.

In most of the oceans, the growth of phytoplankton is limited by nitrogen sources (typically nitrate). In some places, however, where there is adequate nitrogen, phosphorus, and silica (if we are referring to diatoms), the growth of phytoplankton is believed to be limited by the availability of iron. Experiments have, in fact, shown that growth can be increased in some of these areas through addition of iron to the ocean. Many of these experiments are summarized by Frank Millero in his book “Chemical Oceanography” (second edition; 1996).

One of the facts that arises from these studies involves phosphorus. The preferred solution ratio of iron to phosphorus is between 1:100 and 1:1250 for coastal species of phytoplankton, and about 1:10,000 for open ocean species, suggesting that the open ocean species have developed better mechanisms for collecting and/or using iron. I mention this fact not because we can use it quantitatively to know if we have enough iron in our systems, but rather to demonstrate that different organisms have different abilities to fulfill their iron requirements, and that iron may be limiting the growth of one organism, while in the same tank, nitrogen, phosphorus or silica may be limiting to another.

Note that I stated that if the iron is not bound to an organic it would primarily exist as soluble Fe(OH)3. However, in both the oceans and in reef tanks, there are uncounted hordes of organic molecules that bind iron quite strongly. Unfortunately, while the speciation of some metals has been well studied in some fresh water systems (such as copper in certain lakes), the speciation of iron in seawater has not generally been elucidated. I expect this lack of information stems largely from the difficulty in identifying all of the organic species present, in knowing which ones are binding iron, and in the fact that the nature of organic molecules in seawater will vary from location to location, from season to season, and likely even with the time of day.

Good to know.
Thank you!

 

[ReeferDad93]

So safe to say .25 nitrite will not be harmful? Have a new tank and haven’t measured ammonia in weeks. Nitrite holding steady at .25

 

[Randy Holmes-Farley]

So safe to say .25 nitrite will not be harmful? Have a new tank and haven’t measured ammonia in weeks. Nitrite holding steady at .25

Yes, that and much higher values are safe. The 0.25 ppm you report might also just be test error at the low end of the kit.

 

[ShepherdReefer]

Great article Randy Holmes-Farley; taking it all in and might have a few questions on the subject after I get some future testing equipment for other parameters.

 

[Miami Reef]

Nevertheless, elevated nitrate levels can excessively spur the growth of zooxanthellae, which in turn can actually decrease the growth rate of their host coral, and turn them brown.

Can you expand on this? How would excess zooxanthella cause a coral to grow slower? I always thought the more zooxanthella the faster the growth.

 

[Randy Holmes-Farley]

Can you expand on this? How would excess zooxanthella cause a coral to grow slower? I always thought the more zooxanthella the faster the growth.

I don't claim to have a complete understanding of all the issues involved, but this paper suggests that elevated nitrate increases zoox and reduces skeleton growth by limiting CO2 availability to the coral:

[note that in the paper, the highest nitrate tested was only 20 uM = 1.2 ppm]


Nitrate increases zooxanthellae population density and reduces skeletogenesis in corals

Nitrate increases zooxanthellae population density and reduces skeletogenesis in corals - Marine Biology

Very little information exists on the effects of nitrate on corals, although this is the major form in which nitrogen is prescrit in tropical eutrophie coastal waters. In this study we incubated nubbins ofPorites porites and explants ofMontastrea annularis in laboratory photostats illuminated by...

link.springer.com

At the end of this period it was found that the population density of the zooxanthellae had increased significantly with increased nitrate concentration, suggesting nitrogen limitation of the growth rate of zooxanthellae in the control group.


The most dramatic change was in the rate of skeletogenesis, which decreased by ≅ in both species when exposed to nitrate enrichment. A model is presented which suggests that the diffusion-limited supply of CO2 from surrounding seawater is used preferentially by the enlarged zooxanthellae population for Photosynthesis, thereby reducing the availability of inorganic carbon for calcification.

 

[vetteguy53081]

I don't claim to have a complete understanding of all the issues involved, but this paper suggests that elevated nitrate increases zoox and reduces skeleton growth by limiting CO2 availability to the coral:

[note that in the paper, the highest nitrate tested was only 20 uM = 1.2 ppm]


Nitrate increases zooxanthellae population density and reduces skeletogenesis in corals

Nitrate increases zooxanthellae population density and reduces skeletogenesis in corals - Marine Biology

Very little information exists on the effects of nitrate on corals, although this is the major form in which nitrogen is prescrit in tropical eutrophie coastal waters. In this study we incubated nubbins ofPorites porites and explants ofMontastrea annularis in laboratory photostats illuminated by...

link.springer.com

At the end of this period it was found that the population density of the zooxanthellae had increased significantly with increased nitrate concentration, suggesting nitrogen limitation of the growth rate of zooxanthellae in the control group.


The most dramatic change was in the rate of skeletogenesis, which decreased by ≅ in both species when exposed to nitrate enrichment. A model is presented which suggests that the diffusion-limited supply of CO2 from surrounding seawater is used preferentially by the enlarged zooxanthellae population for Photosynthesis, thereby reducing the availability of inorganic carbon for calcification.

Excess zooxanthellae under too much nitrate and even light can be expelled temporarily and has to be restored if I remember correctly at a recent seminar and slows down metabolism of coral until restored

 

[Tangdora]

Hi Randy

Could you elaborate more on you reasoning behind the amended numbers for nitrate and phosphates as compared to your original article http://reefkeeping.com/issues/2004-05/rhf/. Which has always been my go to. Only recently discovered this form where you changed the number Now just curious if the 2-10 ppm nitrate level recommendation is because time has simple revealed successful tanks in this range and therefore acceptable. Or if below 2 is simply hard for some to achieve or vice versa below 2ppm is actually revealing itself to lead to more issues on the flip side. The original article did only have a less than sigh which would imply 0 as good value , which is not necessarily the case these days. Is that why you set a range? Same thought process for the phosphate numbers

Thanks

 

[Randy Holmes-Farley]

Hi Randy

Could you elaborate more on you reasoning behind the amended numbers for nitrate and phosphates as compared to your original article http://reefkeeping.com/issues/2004-05/rhf/. Which has always been my go to. Only recently discovered this form where you changed the number Now just curious if the 2-10 ppm nitrate level recommendation is because time has simple revealed successful tanks in this range and therefore acceptable. Or if below 2 is simply hard for some to achieve or vice versa below 2ppm is actually revealing itself to lead to more issues on the flip side. The original article did only have a less than sigh which would imply 0 as good value , which is not necessarily the case these days. Is that why you set a range? Same thought process for the phosphate numbers

Thanks

The original numbers were based on matching the ocean. That was the best info and target set we had for many years, IMO, and was the general recommendation from most folks. They still work as targets if there are adequate sources of N and P from ammonia and from particulates (plankton, for example), as there seem to be in the ocean. Some folks (e.g., jda) target low levels, as do many zeovit users.

In a reef tank, those are often, but not always, in shorter supply and many folks have found that low N and P seems to work less well than higher values.

FWIW, zero is a concept that I would never have intended, nor can anyone attain it, but it did certainly mean undetectable with kits, which now seems les than optimal in a reef tank despite being true in the ocean.

Hence the change.