tacka google / nordic reef forums.... Reef Crystals Reef Crystals from Aquarium Systems contains additional calcium and other elements. This aims to boost levels over that of natural seawater, making it well suited to the reefkeeper who uses RO. It contains a metal detoxifier to neutralise copper that may be present in domestic water supplies, and has added vitamins. It’s claimed to be the fastest dissolving salt, and has a unique crystal structure. Hawaii Marine Institute’s research: Their research suggested that like the salts on review here, Reef Crystals didn’t produce water of the correct salinity if measured out by weight, being some 6g per litre lower than it should have been. It came out average in most areas with sodium, magnesium, calcium, calcium carbonate, potassium, strontium, chlorine and sulphur levels all very slightly lower than the levels measured in natural seawater. Only boron was present in greater quantities. Nutrients were present in greater quantities than in natural seawater, with phosphate levels over 25 times higher, and ammonia levels 39 times higher. The pH of the prepared saltwater was found to be 9.28, the highest measured. Our tests: We found that the specific gravity was about 1.024 at 25°C and measured the pH at around 8.6. Calcium and magnesium levels were the highest in the test at 446ppm and 1410 ppm respectively. No ammonia, nitrite or phosphate were detected, but we did find 0.2 ppm of nitrate, a minuscule amount really - and most of the other salts tested positive for this too. True to its claims, the salt dissolved very quickly, taking just 90 seconds of stirring to dissolve 35g in one litre of water. At the end, however, a few larger particles appeared to have precipitated and were still present in the water. You say: Reader Simon Orr of Devon was recommended Reef Crystals by a friend and uses it in his reef tank to change about 10% of the water weekly. He rates it very highly for dissolvability, as does reefkeeper Paul Spencer of Hull who appreciates its value for money. John Dalley from Leeds recently changed over to Reef Crystals. “I noticed that with my old salt, when making up water for water changes, which I do in 50 l. black plastic mausers, a white film would appear on the bottom and sides of the mauser. If left uncleaned, this would build up and flake off causing the water to go cloudy. I presumed this was undissolved salts. I get it to a far lesser degree with Reef crystals.”