To avoid both coral inhibition and algae proliferation in seawater, phosphate concentration should be kept below 0.2 mg/L (ppm). In freshwater, phosphate at less than 5 mg/L should pose no problem. Common sources of phosphate in the aquarium are the municipal water supply, fish waste, food, phosphate buffers or pH adjusters, some gravels, and carbon. Phosphate in carbon arises from the organic origin of all carbons (anything that was once living will contain phosphate) and not from acid washing (as is often mis-stated). All carbons, regardless of the manufacturer’s claim to the contrary, contain and leach phosphate, albeit not all to same extent. Unfortunately, the carbons that are better for water purification are usually the carbons that contain the most phosphate, unless they have been pre-washed to remove some of the leachable content. If you are concerned about phosphate and use carbon, pre-soak and wash it for several days in distilled water with a small amount of muriatic acid (enough to keep the pH of the water acid). Remember that phosphate is not at all toxic and that, unless you have either hard corals or have a hair algae problem, there is no need to get neurotic about phosphate. There are phosphate removing products on the market. These products are based on the precipitation of phosphate on the surface of either aluminum oxide (aluminum rust) or iron oxide (iron rust). The aluminum products are white while the iron products are brown. Some aquatic suppliers try to conceal the identity of these materials by giving them other generic identities such as “ceramic.” Aluminum oxide is manufactured as spherical beads. Some aquatic companies sell the intact beads while others sell broken beads that appear as granules rather than beads. For water flow dynamics, the intact beads are geometrically superior. These materials are generally safe and effective. They do, however, remove more than just phosphate. Silicates, organic acids, some amino acids, and some vitamins are also removed. They are more effective in seawater than in freshwater, at higher pH than lower pH. Once something has been bound, it is not released. Once exhausted, none of these materials can be regenerated, regardless of any manufacturer’s claim to the contrary. Phosphate cannot be baked away. If not exhausted, they can be removed, allowed to dry, and reused until exhausted, but this is not regeneration. If you find that you are not exhausting your phosphate remover in bringing your phosphate level to an acceptable level, then use less than the recommended amount rather than repeatedly removing and replacing the material.

What about vitamins and trace additives? Are they really necessary? Or are they harmful?

Two vitamins, C and B₁₂, have been reported as beneficial to corals. Plants and macroalgae usually benefit from vitamins B₁₂, biotin, thiamine, and riboflavin. Plants and algae also require potassium, magnesium, manganese, iron, calcium, strontium, zinc, molybdenum, copper, nickel, cobalt, selenium, rubidium, vanadium, and tin. Some of these are best delivered as chelates to make them more biologically available and prevent rapid precipitation, particularly in seawater. Some are quite toxic at any concentration greater than trace. Fish derive all of their nutrients from food and so do not need supplements in the water. Corals and some invertebrates, as well as plants and algae, can benefit from supplements in the water. It is important not to overdose, particularly with trace elements products. This, after all, is why they are called “trace” elements. The two main vitamins beneficial in the aquarium are vitamins C and B₁₂. A product high in vitamin C, ascorbic acid, will significantly lower redox when added, because vitamin C is a powerful anti-oxidant or reducing agent. Vitamin B₁₂ is very intensely red and even small quantities of it will color the product that contains it pink to red or brown, depending on other components present. If a product claims to contain B₁₂, it should be some shade of red or brown, not blue or green. The only natural components of such a product that would impart a blue or green color are copper and nickel, and if present at a concentration high enough to impart such a color, these products would be toxic.

A synthetic dye could also impart such a color. A crude vitamin source such as algae or cyanobacteria (Spirulina) would also impart a green color from the chlorophyl content. Such a source, however, would be inadequately low in critical vitamins, particularly B₁₂, without further processing. B₁₂ should be the most important component of an aquatic vitamin supplement and when present at suitable concentration it must impart some kind of red coloring to the product. Liquid vitamin products are highly susceptible to oxidation and microbial contamination. It is important that they contain chemically stabilized components, and incorporate preservatives, or be sterile, or both. You may think you prefer a product that is “all natural” and without preservatives, but such a liquid vitamin product would quickly spoil unless sterile and refrigerated.

How can I recognize self-serving pseudo-scientific goobledy-gook when I see it?

First, consider the source. What are the credentials or experience? Does the author have a financial interest or political agenda in persuading you to buy something you may not need or following a specific course? This is not to say that everyone associated with or owning stock in a commercial aquatic enterprise is out to deceive you, but you should exercise a critical eye. Remember that hobbyist magazines are not what the scientific community refers to as “peer reviewed” journals. It is not unusual for a lot of nonsense to make it into print. Seeing and assertion in print does not make it true. These magazines serve a very useful function and I do not suggest that they should be replaced by peer reviewed journals or that you should not avail yourself of them, only that articles that appear in them reflect the perceptions and misperceptions, judgments and misjudgments, views and biases of the authors and do not necessarily reflect a consensus of experts or even that of the magazine. Bear in mind, too, that even the “experts” are not always as expert as they may seem.
Does the author rely on well reasoned, logical thought sequence to back up his assertions or does he rely on name dropping or supposed citations from authority figures? To my knowledge, neither the Pope nor the National Academy of Sciences ever made any pronouncements relative to aquariums. If citations to the literature are made, are they citations to the scientific literature or to other unsubstantiated articles. Are the citations relevant? Beware of materials taken out of context: e.g., the chemistry of nitrogen compounds in air under extreme conditions or on radiation exposure does not apply to aqueous conditions.
Does the author just guess that something is effective or does he actually do the arithmetic? For example, has anyone recommending the use of calcium hydroxide (limewater) to raise calcium ever computed the actual calcium content of limewater and what impact a given volume will have on a given aquarium volume? I have and it is remarkably insignificant. Assuming a maximum content of 270 mg/L calcium (under the best conditions!), adding half a gallon of limewater to 10 gallons of seawater will raise the calcium by less than 14 mg/L, not counting what it would do to the pH.
Are assertions based on anecdotal evidence involving few people who have not actually conducted controlled experiments but instead have changed multiple variables at the same time such that it is impossible to discern what is actually occurring? Does the author recommend the use of certain materials without identifying them or recommending some generic sources, or does he recommend some expensive aquatic version? For example, if limewater is recommended, are you told it is generally available cheaply as “pickling lime” at any grocery store; or calcium chloride, are you told it is available very cheaply as “road salt” pellets at your local hardware store? Or are you told these sources are not sufficiently pure? The facts are that these materials are no less pure than sources bottled specifically for the hobbyist. Does the author make inconsistent recommendations? For example, that you use a vitamin C additive on a regular basis and that you use potassium permanganate to raise your redox whenever it falls below a recommended value.