Reef KeepingReef Keeping

Top ten most Top ten most costly mistakescostly mistakes

If you decide to make a salt water If you decide to make a salt water aquarium it can be a little aquarium it can be a little intimidatingintimidating

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96.5% water96.5% water 3.5% salt by weight3.5% salt by weight Even ions at low concentration are Even ions at low concentration are

important to ocean organismsimportant to ocean organisms With the salts comes water With the salts comes water

changes…density, conductivity, and changes…density, conductivity, and refractive indexrefractive index

The index of refraction (or refractive The index of refraction (or refractive index) is the ratio of the speed of light index) is the ratio of the speed of light traveling through a vacuum to the speed traveling through a vacuum to the speed of light in the material being tested. Most of light in the material being tested. Most aquarists do not realize that when using aquarists do not realize that when using a refractometer, they are measuring the a refractometer, they are measuring the speed of light through their aquarium's speed of light through their aquarium's water, so having such knowledge might water, so having such knowledge might be a good way to impress friends with be a good way to impress friends with your technical abilities! your technical abilities!

Light travels through most materials more Light travels through most materials more slowly than it does through a vacuum, so their slowly than it does through a vacuum, so their refractive index is higher than 1.00000. The refractive index is higher than 1.00000. The detailed mathematics and physics behind detailed mathematics and physics behind refractive index are actually quite complicated, refractive index are actually quite complicated, because it is often a complex number with real because it is often a complex number with real and imaginary parts, but a simple version is and imaginary parts, but a simple version is adequate for all purposes that a reef aquarist adequate for all purposes that a reef aquarist would encounter. Some materials slow light would encounter. Some materials slow light traveling through them more than others, and traveling through them more than others, and slower light travel leads to a higher refractive slower light travel leads to a higher refractive index. Table 1 shows some typical refractive index. Table 1 shows some typical refractive index values for comparative purposes.index values for comparative purposes.

Table 1. Index of Refraction of Table 1. Index of Refraction of Various Materials.Various Materials.

Vacuum1.0000Vacuum1.0000 Air 1.0003Air 1.0003 Water (pure)1.3330Water (pure)1.3330 Seawater (35 ppt)1.3394Seawater (35 ppt)1.3394 Ethyl alcohol 1.361Ethyl alcohol 1.361 Sugar solution (80% sugar)1.49Sugar solution (80% sugar)1.49 Glass (soda lime)1.510Glass (soda lime)1.510

In solutions of two compounds, such as In solutions of two compounds, such as ethyl alcohol in water, sugar in water or ethyl alcohol in water, sugar in water or salt in water, the refractive index salt in water, the refractive index changes in step with how much of each changes in step with how much of each component is present. component is present.

refractometers are used in brewing, refractometers are used in brewing, sugar refining, analyzing blood and sugar refining, analyzing blood and urine protein and many other industries urine protein and many other industries where a quick measure of refractive where a quick measure of refractive index can lead to a good assessment of index can lead to a good assessment of what is present.what is present.

It cannot tell you what the molecule It cannot tell you what the molecule is but it can give you an idea of how is but it can give you an idea of how muchmuch

Price range Price range refractometer100-200 refractometer100-200

dollarsdollars Aquarists can use the effects that Aquarists can use the effects that

added salts have on the refractive added salts have on the refractive index of a water solution to index of a water solution to determine the salinity of reef determine the salinity of reef aquarium water. As the salinity of aquarium water. As the salinity of seawater rises, the amount of salt seawater rises, the amount of salt added rises, so the refractive index added rises, so the refractive index rises. rises.

ConductivityConductivity

How well electrons How well electrons move through the move through the water…or how well water…or how well electricity moves electricity moves through the waterthrough the water

NaCl density(W / V)

%

Conductivity(mS / cm)

NaCl density(W / V)

%

Conductivity(mS / cm)

0.1 2.0 1.1 19.2

0.2 3.9 1.2 20.8

0.3 5.7 1.3 22.4

0.4 7.5 1.4 24.0

0.5 9.2 1.5 25.6

0.6 10.9 1.6 27.1

0.7 12.6 1.7 28.6

0.8 14.3 1.8 30.1

0.9 16.0 1.9 31.6

1.0 17.6 2.0 33.0

Refractive index, conductivity, and Refractive index, conductivity, and density can all be used by someone density can all be used by someone keeping a reef (aquarium) to test for keeping a reef (aquarium) to test for salinity.salinity.

90-600 dollars90-600 dollars

4 Main Ions4 Main Ions

ChlorideChloride SodiumSodium SulfateSulfate magnesiummagnesium

Natural Seawater for a Natural Seawater for a reefreef

Collect it yourself but important Collect it yourself but important factors …how pure it was at collection factors …how pure it was at collection and how pure it remained until use.and how pure it remained until use.

Collect the water offshore to avoid Collect the water offshore to avoid runoffrunoff

Or collect from a rising tideOr collect from a rising tide Coastal waters have a lot of Coastal waters have a lot of

chemicals and pathogenschemicals and pathogens

If natural seawater is stored too long If natural seawater is stored too long and it stagnates .…..the break down of and it stagnates .…..the break down of organic molecules can produce toxic organic molecules can produce toxic substances.substances.

It is better to use immediatelyIt is better to use immediately

Artificial SeawaterArtificial Seawater

It is probably ok just to use the It is probably ok just to use the cheapest you can get in a salt mix for cheapest you can get in a salt mix for an aquariuman aquarium

Do not use sea salt for cooking it is Do not use sea salt for cooking it is usually to low in magnesiumusually to low in magnesium

It is hard to match the concentration It is hard to match the concentration of the less common ions in a salt mixof the less common ions in a salt mix

Everyone has their own opinion about Everyone has their own opinion about which salt mix is bestwhich salt mix is best

Prices range 25-115 Prices range 25-115 dollarsdollars

In order to add the most common In order to add the most common ions to waterions to water

It takes a lot of material. Unless they It takes a lot of material. Unless they are in pure (very expensive) form are in pure (very expensive) form they will put a lot of impurities in the they will put a lot of impurities in the water.water.

To be honest, the evidence for using To be honest, the evidence for using one salt mix over another is marginal one salt mix over another is marginal at best.  Certainly some are better, at best.  Certainly some are better, and some may be bad, but no simple and some may be bad, but no simple ranking can be made.  Every artificial ranking can be made.  Every artificial salt mix varies from natural seawater's salt mix varies from natural seawater's concentrations of some ions.  concentrations of some ions. 

many that claim to try to match many that claim to try to match seawater actually do a surprisingly seawater actually do a surprisingly poor job, and differ alot. poor job, and differ alot. 

More expensive salt mixes can More expensive salt mixes can theoretically do a better job by theoretically do a better job by purchasing purer raw materials, but purchasing purer raw materials, but that does not ensure that those that does not ensure that those companies do so. companies do so.

matching natural seawater, is the matching natural seawater, is the problem. Nproblem. Noneone really does, and it really does, and it becomes very difficult to decide what is becomes very difficult to decide what is best. best. 

For example, is it better to have too For example, is it better to have too much sulfate or too little fluoride?  much sulfate or too little fluoride? 

Too much strontium or too little Too much strontium or too little potassium?  No one knows.  Ask that potassium?  No one knows.  Ask that question about nearly every chemical question about nearly every chemical constituent, and the true answer is, “No constituent, and the true answer is, “No one knows one knows

So which to useSo which to use

It is probably best to ask people that It is probably best to ask people that have made successful tanks have made successful tanks before……In a poll I have taken 9 before……In a poll I have taken 9 people used instant ocean and 7 people used instant ocean and 7 used Reef Crystals and the rest were used Reef Crystals and the rest were divided up into 1 person each with a divided up into 1 person each with a different branddifferent brand

Pure WaterPure Water

In addition to using a suitable salt In addition to using a suitable salt mix, it is important to use suitably mix, it is important to use suitably pure freshwater, both for making pure freshwater, both for making salt mixes and for topping-off for salt mixes and for topping-off for evaporative losses.   . evaporative losses.   .

The majority of experienced and The majority of experienced and successful reef aquarists in the U.S. successful reef aquarists in the U.S. appear to use RO/DI (reverse appear to use RO/DI (reverse osmosis/deionization) to purify tap osmosis/deionization) to purify tap water. water. 

Prices range 100-300 Prices range 100-300 dollarsdollars

Reverse osmosis (RO) alone may be Reverse osmosis (RO) alone may be adequate in some cases, but not adequate in some cases, but not always. always.

The use of tap water itself entails a number of The use of tap water itself entails a number of concerns besides the presence of chlorine.  concerns besides the presence of chlorine. 

First is Chloramines which does not dissipate First is Chloramines which does not dissipate after sitting around, the way many aquarists after sitting around, the way many aquarists have done in the past for chlorine.  It is now have done in the past for chlorine.  It is now being added to many water supplies, and is being added to many water supplies, and is much longer lived than chlorine.  much longer lived than chlorine. 

It also requires special treatments, not just the It also requires special treatments, not just the standard dechlorinating agents.  Other standard dechlorinating agents.  Other concerns with tap water are copper (which concerns with tap water are copper (which often comes from your home's plumbing), often comes from your home's plumbing), nutrients (nitrate and phosphate) and alkalinity nutrients (nitrate and phosphate) and alkalinity (which is not (which is not per seper se a problem, but can boost a problem, but can boost levels too high in some cases). . levels too high in some cases). .

Chloramines can be removed by Chloramines can be removed by means of a granular active carbon means of a granular active carbon filter filter

ChloramineChloramine (monochloramine) is a (monochloramine) is a chemical compound with the formula chemical compound with the formula NH2Cl. It is usually used as a dilute NH2Cl. It is usually used as a dilute solution where it is used as a solution where it is used as a disinfectant. disinfectant.

Chlorine combines with ammoniaChlorine combines with ammonia

In general, I recommend avoiding In general, I recommend avoiding tap water.  Sure, some folks use it tap water.  Sure, some folks use it and have fine aquaria. Just safer in and have fine aquaria. Just safer in the long run.the long run.

Typical commercial distilled water is Typical commercial distilled water is likely acceptable, as long as it has not likely acceptable, as long as it has not been exposed to metals such as copper been exposed to metals such as copper in condensers, pipes or holding tanks.  in condensers, pipes or holding tanks.  Unfortunately, it is not easy to know the Unfortunately, it is not easy to know the production history of distilled water, and production history of distilled water, and testing with most copper test kits may testing with most copper test kits may be inadequate because they may not be inadequate because they may not accurately read low enough to detect its accurately read low enough to detect its presence. presence.

Many aquarists use water provided Many aquarists use water provided by machines at grocery stores or by machines at grocery stores or from their local fish stores.  Many of from their local fish stores.  Many of these are apparently reverse these are apparently reverse osmosis (RO) water. osmosis (RO) water. 

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natural ocean water has an average natural ocean water has an average salinity of about 35 ppt, salinity of about 35 ppt, corresponding to a specific gravity corresponding to a specific gravity of about 1.0264 and a conductivity of about 1.0264 and a conductivity of 53 mS/cm.  Salinity can vary of 53 mS/cm.  Salinity can vary substantially from place to place. substantially from place to place.

As far as I know, little real evidence As far as I know, little real evidence suggests that keeping a coral reef suggests that keeping a coral reef aquarium at anything other than aquarium at anything other than natural salinity levels is preferable. natural salinity levels is preferable.

It appears to be common practice to It appears to be common practice to keep marine fish, and in many cases keep marine fish, and in many cases reef aquaria, at somewhat lower reef aquaria, at somewhat lower than natural salinity levels. This than natural salinity levels. This practice stems, at least in part, from practice stems, at least in part, from the belief that fish are less stressed the belief that fish are less stressed at reduced salinity. at reduced salinity.

Substantial misunderstandings also Substantial misunderstandings also arise among aquarists as to arise among aquarists as to how specific gravity really relates to how specific gravity really relates to salinitysalinity, especially considering temperature , especially considering temperature effects.effects.

Specific gravity versus Specific gravity versus slainity slainity

One question that every marine aquarist One question that every marine aquarist faces is the amount of salt to add to the faces is the amount of salt to add to the tank. Most beginning texts choose to tank. Most beginning texts choose to describe the salinity in terms of specific describe the salinity in terms of specific gravity, and go on to relate how one gravity, and go on to relate how one measures it with a hydrometer. While not measures it with a hydrometer. While not nearly as precise as measuring salinity with nearly as precise as measuring salinity with a conductivity probe or a refractometer, a conductivity probe or a refractometer, hydrometers are chosen by many because hydrometers are chosen by many because they are inexpensive and easy to use. they are inexpensive and easy to use.

Hydrometer measures Hydrometer measures density or specific gravitydensity or specific gravity

For many aquarium purposes, they For many aquarium purposes, they are perfectly adequate.are perfectly adequate.

The wonderful world of The wonderful world of spcific gravityspcific gravity

One question that every marine One question that every marine aquarist faces is the amount of salt aquarist faces is the amount of salt to add to the tank. Most beginning to add to the tank. Most beginning texts choose to describe the salinity texts choose to describe the salinity in terms of specific gravity, and go in terms of specific gravity, and go on to relate how one measures it on to relate how one measures it with a hydrometer. with a hydrometer.

While not nearly as precise as While not nearly as precise as measuring salinity with a measuring salinity with a conductivity probeconductivity probe or a or a refractometer, hydrometers are refractometer, hydrometers are chosen by many because they are chosen by many because they are inexpensive and easy to use. For inexpensive and easy to use. For many aquarium purposes, they are many aquarium purposes, they are perfectly adequate.perfectly adequate.

Why is specific gravity useful to Why is specific gravity useful to aquarists? Primarily because it is a simple aquarists? Primarily because it is a simple and quantitative way to tell how much of and quantitative way to tell how much of something is in water. If things less dense something is in water. If things less dense than water are dissolved in it, then the than water are dissolved in it, then the specific gravity will drop. Ethanol, for specific gravity will drop. Ethanol, for example, is less dense than water, and example, is less dense than water, and makes the specific gravity drop. This fact makes the specific gravity drop. This fact is used by brewers to gauge the amount is used by brewers to gauge the amount of alcohol in their brews.of alcohol in their brews.

Likewise, if things denser than water are Likewise, if things denser than water are dissolved in it, the specific gravity goes up. dissolved in it, the specific gravity goes up. Nearly all inorganic salts are denser than Nearly all inorganic salts are denser than water, so dissolving them in water makes water, so dissolving them in water makes the specific gravity rise. This rise can be the specific gravity rise. This rise can be used by aquarists to gauge how much salt used by aquarists to gauge how much salt is in their water. Of course, it cannot tell is in their water. Of course, it cannot tell you what is in the water, but if you are you what is in the water, but if you are using an appropriate salt mix, it can tell using an appropriate salt mix, it can tell you how much is there and whether it you how much is there and whether it approximates natural seawater or not. approximates natural seawater or not.

1. Make sure that the hydrometer is completely clean (no salt deposits) 1. Make sure that the hydrometer is completely clean (no salt deposits) and that the part of the hydrometer above the water line is dry. and that the part of the hydrometer above the water line is dry. Tossing it in so it sinks deeply and then bobs to the surface will leave Tossing it in so it sinks deeply and then bobs to the surface will leave water on the exposed part that will weigh down the hydrometer and water on the exposed part that will weigh down the hydrometer and give a falsely low specific gravity reading. Salt deposits above the give a falsely low specific gravity reading. Salt deposits above the water line will have the same effect. If any deposits won’t easily water line will have the same effect. If any deposits won’t easily dissolve, try washing in dilute acid (such as vinegar or dilute muriatic dissolve, try washing in dilute acid (such as vinegar or dilute muriatic acid)acid)

2. Make sure that there are no air bubbles attached to the hydrometer. 2. Make sure that there are no air bubbles attached to the hydrometer. These will help buoy the hydrometer and yield a falsely high specific These will help buoy the hydrometer and yield a falsely high specific gravity reading.gravity reading.

3. Make sure that the hydrometer is at the same temperature as the 3. Make sure that the hydrometer is at the same temperature as the water (and preferably the air).water (and preferably the air).

4. Read the hydrometer at the plane of the water surface, not along the 4. Read the hydrometer at the plane of the water surface, not along the meniscus (Figure 4; the meniscus is the lip of water that either rises up meniscus (Figure 4; the meniscus is the lip of water that either rises up along the shaft of the hydrometer, or curves down into the water, along the shaft of the hydrometer, or curves down into the water, depending on the hydrophobicity of the hydrometer).depending on the hydrophobicity of the hydrometer).

5. Rinse with freshwater after use to reduce deposits.5. Rinse with freshwater after use to reduce deposits. 6. Do not leave the hydrometer floating around the tank between uses. 6. Do not leave the hydrometer floating around the tank between uses.

If you do, difficult to remove deposits may form over time.If you do, difficult to remove deposits may form over time.   

How to Use a Swing Arm HydrometerHow to Use a Swing Arm Hydrometer In addition to those described above, here are some In addition to those described above, here are some

special tips for swing arm hydrometers:special tips for swing arm hydrometers: 7. Make sure that the hydrometer is completely level. 7. Make sure that the hydrometer is completely level.

A slight tilt to either side will change the reading.A slight tilt to either side will change the reading. 8. The Deep Six hydrometer recommends 8. The Deep Six hydrometer recommends

"seasoning" the needle by filling it with water for 24 "seasoning" the needle by filling it with water for 24 h prior to use. Presumably this permits the water h prior to use. Presumably this permits the water absorbed into the plastic to reach equilibrium. In the absorbed into the plastic to reach equilibrium. In the case of the hydrometer tested in this paper, the case of the hydrometer tested in this paper, the reading became slightly less accurate after reading became slightly less accurate after seasoning.seasoning.