Fritz Reef Pro Mix (RPM) has quickly become one of the most popular seawater salt mixes in the United States, both for its consistency, affordability and the simple fact that it is becoming widely available at finer reef aquarium stores everywhere. Most veteran RPM users, ourselves included, have appreciated the balanced levels of Ca, KH and Mg that this salt mix provides but Fritz has been developing a new version called RPM High Alk which provides a higher concentration or buffering elements.
For much of my reef keeping experience I’ve leaned towards the most natural seawater salt mix, that is those which mix up to be as close to natural seawater levels as possible. This is fine for the vast majority of fish and reef aquariums, but for those setups that are chock full of fast growing stony corals, ‘enriched’ formulas can help to keep our precious mineral balance pegged.
The value of a higher alk salt mix has become more apparent as one of my 60 gallon reef tanks has seen explosive growth of SPS corals within it, and an accelerating demand for major elements, most prominently those that constitute alkalinity. At present this system is consuming around one liter of high concentration buffer every two weeks, and it’s all I can do to maintain an alkalinity of 7dKH.
I’m one of those reefers that uses water changes as an essential part of my maintenance routine so the notion of being able to do water changes with new salt water that will help increase alkalinity is very attractive. Surely a lot of commercial coral growers and dealers will also appreciate using an affordable seawater mix such as RPM high alk with a ‘native’ alkalinity of 10 to 12dKH.