Low Alk and Mag when mixing H20 salt to 1.025

Question:

i have read and heard a lot of positive response about this salt so i researched it a little more before deciding to switch from the current IO salt brand that i use. what i based my final decision on was the fact that all the levels were suppose to be where they are suppose to be when the salt was mixed to an SG of 1.025 at a temp of 78. unfortunately they are not. i tested ph, alk, mag, and calcium with 2 different sets of kits. the kits were a little off from each other but they both were way off from what the directions say. the only thing that was ok was the ph at 8.3. the alk was around 11, mag around 1100 and calcium was only at 380. i purchased this salt so i wouldnt have to add anything to bring up the levels. i have been in this hobby for about 5 years and when i purchase a product i expect it to deliver what it says it will. the lot number on the bucket says 504276. unless we can resolve this issue, i will no longer be purchasing any products from this company.

thank you, Eric

Answer:

Hi Eric

Thank you for using D-D H2Ocean reef salt and i hope i can help you with your query.

Each 1 Ton batch of H2Ocean reef salt is laboratory tested before it leaves the factory and as such should be

within our quoted specifications.

In instances that levels are low we have found that in the main this is down to either low salinity of the water mix, precipitation due to certain mixing methods or low/high levels of certain elements due to separation within the bucket caused by transport vibration.

Let’s look at each scenario in greater detail.

1. Salinity.

This is the most common cause of low levels as if salinity is low the element concentration will also be low. There are two aspects of salinity measurement that can and do cause low salinity.

a. If measuring by Specific Gravity there is often much confusion over the correct S.G to run a reef tank to achieve full strength sea water

inline with the average throughout the world. We must remember that Specific gravity is temperature dependent, this means that as water expands or contracts due to temperature the specific gravity will change. This is why we strongly suggest that hobbyists use the PPT scale(parts per thousand) as this scale isn't temperature dependant.

So with this in mind you want to aim for 35PPT for the Seawater standard or 35.5PPT when using H20 salt, this equates to 1.0264 S.G at 25c or 1.0266 at 20c at 35 PPT, you will notice that the Specific Gravity changes with temperature whilst the PPT measurement remains constant as it weight based rather than volume/temp. This is important when using equipment to test salinity that has been calibrated to a certain temperature.

As H2Ocean includes slightly higher Magnesium than the seawater we suggest aiming for 35.5PPT.

For instance if using a refractometer designed to read the sample at 20c the required S.G would be 1.0266 at 35PPT , if using a equipment calibrated at 25c you would aim for 1.0264 S.G. In both instances the PPT scale will remain the same at 35PPT.

So to sum up aim for 35.5PPT if using a refractometer to achieve the correct concentration of elements and salinity but take into account the info below in b.

b. The next issue that would add to low salinity would be if you are using a refractometer designed to measure brine. Most hobbyists do not realise that the majority of refractometers available to the hobby are actually ported over from the food industry and are designed to measure the refractive index of brine. At D-D we have had a refractometer specifically designed to measure seawater as due to its more complex elemental make up its refractive index is different from that of brine( plain NaCl and water).

If using a brine refractometer you will find that it will read around 1.5PPT too high due to the offset of being designed for the refractive index of brine. To counter this please calibrate the refractometer with RO water as per manufacturers instruction and then include the1.5PPT offset when taking a reading from the refract. This will equate a reading of 37PPT, the real salinity will infact be at 35.5PPT(seawater).

You may find the following link interesting:

http://www.theaquariumsolution.com/specific-gravity-salinity-and-its-measurement

2. Mixing

For best results mix our salt into cold RO water whilst running a strong pump. If the water contains a heater and is warm it can cause seed crystals of calcium carbonate to form and a cascade effect of precipitation. Slowly add the salt into the water, i tend to shake the salt in to avoid clumping which would cause super saturation of salts at the water to clump interface and again cause precipitation.

Once the salt has mixed clear make adjustments to the salinity then bring up to temperature and allow to mix for 24 hours before testing or adding to the tank. Freshly mixed water can be a little caustic and give sporadic test results due to elements not mixing totally and tiny un dissolved dusty salt particles upsetting the test reagents, so always allow the salt to mix before testing as above.

3. Transport vibration.

As our salt is often transported many thousands of miles it can be subject to transport vibration. When this happens heavier elements can vibrate down to the bottom of the bucket. This usually results in a mix where certain elements such as Magnesium can be low at the first few inches of the salt whilst concentrations can increase above spec towards the bottom of the bucket.

With this in mind please give the salt a good mix before use, preferably part the salt into separate buckets then mix back in together.

I hope that my email will prove helpful and i feel in this case that the cause of the Low Mag and calcium will be due to low salinity. I realise that your Alk results are higher than might be expected but mix to the new salinity for 24 hours and test again. If you find the Alk is still high cross reference with another kit and if using a Salifert kit check the kit with the included reference solution as i have always found that the Salifert kits have historically measured 0.7-1.0 dkh too high for me.

Regards Tony