Guys I am pleased to hear you are using our salt over there but very surprised by the results you are getting. I would like to say that it is impossible to have such a low Magnesium reading however impossible is a strong word and there can always be one off mistakes made. If this is the case then it is the first time we have had this issue in about 250 tonnes of salt since February. The salt is made in 1 tonne batches and tested at the factory and we also retain a sample of every batch. So we can go back and retest the levels in the laboratory. Can you please post your batch numbers on the forum which are written on the enclosed instruction sheet, so that I can have it checked? It is likely that you all have the same batch. Whilst we are checking the parameters again I would like you to recheck your own tests and hopefully learn a few things from the further information below. SALINITY The levels on the salt are given at a salinity of 1.025 at 25C. To measure this salinity with a refractometer you must aim for a reading of 1.0262 as a refractometer will always measure as if the water is at 20C. If you read our salt instructions you will see how to calibrate the refractometer properly which say that the instrument must be at 20C during calibration and not the water. When you then take a reading the REFRACTOMETER will always measure the SG as if the water is at 20C as the small amount of water that you add to the slide will have no impact on the temperature of the equipment and will soon change to the same temperature as the refractometer. What ATC ( auto temperature compensation) means is that once calibrated at 20C you can use the refractometer in higher ambient temperatures where the instrument is hotter or colder. If you use a HYDROMETER which is calibrated at 25 then you must have the water at 25C to get a reading of 1.025 at 25C, (check the calibration temperature printed on the hydrometer). If the water is colder than 25C then you can use the chart on the salt instructions to work out what the salinity must be at that lower temperature so that when you warm it to 25 it drops to 1.025. Complicated stuff but simple when you understand it. Whilst writing this reply I have realised that the temperature chart has a mistake on it. It should say on the right hand column “hydrometer calibrated at 25C” and not “SG calibrated at 20C”. I changed this as the most common measuring tool was a refractometer however as I have already explained – a refractometer will always read as if the water is 20C and so you always must aim for 1.0262 if you want 1.025 at 25C. TESTING What we also found during development was how difficult it was to get accurate testing and we tried a lot of hobby kits against water samples measured in the laboratory. We even sent the same water off to a number of laboratories as 2 separate blind samples and got different results on some parameters, (not on magnesium), on the same water, so if laboratories find it hard to measure then what chance have we with hobby test kits. What we did conclude is that the Tropic Marine Calcium/Magnesium Test Kit was the most reliable and accurate of the kits that we tried and agreed with the laboratory for magnesium every time. This is not the easiest kit to use and obtains a magnesium reading having first measured the calcium level. You therefore get 2 results with one test kit. Other test kits we found could often be variable and sometimes out by up to 10% either way, although we did not test all manufacturers’ kits. DEVELOPMENT To give some further background information for you guys we developed the required formulation for this salt following a lot of work in David Saxby’s 3500g aquarium system. A couple of years ago David started balancing the salt in his aquarium to natural levels using daily additions of magnesium, calcium and buffer and determined the rates at which the levels would fall. What he found was that with the magnesium you needed to add a lot of additive initially to get it up to a 1350 level but once there it was easy to maintain. With the high (natural) magnesium level he found it much easier to maintain his calcium level and in fact went from running 2 of the largest Deltec PF1001 calcium reactors at almost 24-7 to one running for only about 16 hours per day. Now that David uses our own salt he has been running his tank for 6 months now without the need to make any further additions of magnesium and relies on the calcium reactor alone for calcium and buffer additions. David does a 15% water change every 4 weeks which is about 500 gallons at a time on his 3500g system. I hope this has enlightened you on the salt and its testing a little and apologise that this reply is posted in English. As soon as I have some batch numbers from you then I will get you some more feedback. We have total confidence in our product which is why we are possibly the only company to print the levels and normal expected variance on our buckets. If there is a mistake on this batch then we will of course replace the salt for you through your retailer. All the best Stuart
