Saltwater Reef Aquariums and Trace Elements: The truth By Tom Lang People are being sold a bill of goods. A bunch of hooey. A load of … Well, you get the picture. Coming home from a consultation I had completed for a woman’s reef aquarium the other day, I reflected on the nicely typed list that her local fish store had given her. It was not a list of things to do to maintain her aquarium properly, but rather a long list of additives they are suggesting she add to her aquarium water on a daily basis. Everything from “Essential Elements” to “Micro-vert Food,” this lady was adding capful after capful of concoctions that cost anywhere from $10 to $20 a bottle. Calculating the annual amount she would have to spend for these additives based on the recommended daily dosages, I could certainly see why the store was motivated to keep her using these products. Never mind that she didn’t need any of them. Never mind that their use was causing, not correcting, some chemical imbalances in her system.
Coral reefs, ecosystems even more diverse than terrestrial rainforests, evolved over millions of years in incredibly stable, balanced environments. To be sure, there have been changes in the seas, but these have historically taken place over millennia. Most of the tropical marine fish and invertebrates we keep in our aquariums simply cannot tolerate chemical parameters that vary on a daily or even yearly basis. But what are the important parameters? We know that coral skeletons contain every trace element found in seawater, but the major components are calcium and bicarbonates (Borneman, 2001). If we test for these in reef aquarium water, we find that over time calcium and bicarbonates are depleted. This makes sense since corals use these elements to build their calcium carbonate skeletons. Tests have shown the other trace elements in our aquariums are rarely depleted from their already elevated levels and there is simply no need to supplement them. So, since we have determined that reef aquariums only need additions of calcium and bicarbonates, what do you buy from the local fish store? Why fish, corals, synthetic sea salt and test kit refills, of course. I add Mrs. Wage’s pickling lime at $4 - $5/lb. from the grocery store to freshwater and use this solution to compensate for evaporation. This takes care of the calcium and the one bag lasts me well over a year. Then I add Arm & Hammer baking soda dissolved in a cup of freshwater to take care of the bicarbonates.
Once the proper levels are achieved, it is fairly simple to figure maintenance levels of calcium and bicarbonate for any given aquarium based on the monthly test result trends. Every reef aquarium has different depletion rates based on what organisms are being kept and their collective uptake requirements for growth. It follows that the quantities of calcium and bicarbonates needed to maintain optimal levels might vary considerably from one aquarium to the next. Hopefully the information in this article will help save you some money if you are keeping a reef aquarium. Even more importantly, however, you will have gained some insight into what is needed to keep the animals in your charge happy and healthy. Copyright 2003 by Tom Lang. Used with permission. All rights reserved. (Fish & Marine Life Consultant Tom Lang, PHAqua, began keeping fish in aquariums in the fifth grade when a teacher sold him a complete ten-gallon tank. From there, after completing his education, he worked for several aquarium fish retailers and went on to establish Aquarius Aquarium in 1980 with his wife, Aletha. Their company provides aquatic system design and consultation services and maintains aquariums for clients throughout Central California. As a future source of aquarium-bred fish, corals and other aquatic organisms, Tom and Aletha have also just founded the nonprofit 501(c)(3) Aquarius Aquarium Institute, which seeks to expand captive aquarium propagation to relieve the pressures of taking organisms from imperiled natural ecosystems and to educate the public about important issues in the aquarium industry.) Other Resources AquariumHobbyist.com has a full line of species forums where you can discuss fish species with other owners, and hobbyists.
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The fact is, based on published chemical assays conducted on freshly mixed synthetic seawater by Craig Bingman, Ph.D. (1999), Marlin Atkinson, Ph.D. (1998) and others over the years indicate saltwater made up for aquariums using the major brands actually has greater quantities of trace elements than are found in natural seawater. By adding to these already elevated levels, the unsuspecting reef aquarium hobbyist is not only wasting money, but also creating a chemical soup that bears less and less resemblance to the chemistry of the real ocean over time.
And how do I know how often and how much to add? By simply testing my reef aquarium water with a calcium test kit and an alkalinity test kit once a month, I can measure the levels and calculate depletion rates. Since natural seawater around coral reefs contains anywhere from 380 – 450ppm calcium and has an alkalinity of around 2.8 millequivilents/liter (Borneman, 2001), these are my target levels. I have found that by raising my alkalinity a bit higher (3.5mEq/l) with baking soda, I can keep it from dropping below 2.8 over the course of the month as my stony corals grow and use the bicarbonate at a fast rate. In my experience, this higher level is not so far off natural seawater to have any detriment.