Phosphate & Borate in Synthetic Seawater

Periodically self proclaimed aqua-gurus provide false information regarding marine aquarium products. The latest bogus information attacks some marine salts and the elements phosphorus/phosphate and borate.

The independent S-15™ Report™ indicates that: Marine Environment® dual phase formula™, BIO-SEA® Marinemix and Coral Marine™ (1) Scientific Formula™ are three brands of marine salts that test at <0.003 ppm. of phosphate. That is considered ZERO PHOSPHATE.
There is great concern among marine fish and reef aquarium keepers regarding phosphate found in some brands of marine salts.

Phosphate is found in natural seawater at about 0.07 ppm. or 295 tons per cubic mile.

There are two forms of phosphate:
a) inorganic b) organic. Unfortunately,
the majority of aquarium hobbyists kits marketed for testing phosphate cannot discern between inorganic and organic forms of phosphate.

Inorganic phosphate “could” be added to a synthetic seawater formulation. If that ‘working solution’ was destined only for use in a closed re-circulating system (salt water aquarium) that housed certain specific specimens that required some select form or forms of phosphate, or in an aquarium that was suffering from under lighting.

Inorganic phosphate can be added to a synthetic sea water preparation that is used in an aquarium that is under-lit. Phosphate foments the growth of some algae. In a marine aquarium that is properly lit, the inclusion of phosphate will result in hair algae, “plating” and/or “ring around the tank” with heavy deep green alga. In most marine aquatic applications, this is undesirable.

Healthy salt water aquariums use the best marine salts. These salts are low in phosphates and borate. Water changes reduce accumulated waste ions, like phosphate low and replenish essential elements that are metabolized by the biological filter as well as your captive marine animals.
Organic phosphate is a naturally occurring by-product of a biologically active marine aquarium. This form of phosphate should be the greatest concern of marine fish and reef aquarium keepers. The best way to reduce the natural buildup of organic phosphate and other waste ions is through routine water changes, utilizing a high quality marine salt, that is void of organic phosphate.

Regular water changes will reduce the buildup of waste ions and replenish major, minor and trace elements that are consumed by the metabolic intake of animals on display. Some elements are also depleted by the activity of a biological filter, chemical filtration and/or protein skimming.

It is essential to use a marine salt that is formulated without phosphates. A quality marine salt will contain all elements found in natural sea water (NSW), at levels comparable found in nature. Many marine salts claim to contain all elements or dozens of trace elements found in seawater. The fact is that most marine salts are basic mixtures of major or bulk salts. Some add a few low cost minor ions. Most rely on impurities as a form of ‘trace elements’ to make their packaging and advertising claims, colorable. These trace impurities are described as ‘ions in a free form’, and do not stay in solution.


There are several forms in which borate can be added to a synthetic seawater formulation. Some forms are: sodium borate and boric acid.

Borate is found in natural seawater at about 4.6 ppm.
or 20, 180 tons per cu. mile.

Borate can be used in marine salts to assist in pH control and to a degree pH stabilization. Borate was added to early synthetic seawater formulations. It is still used in some brands of marine salts.

Buffer + dKH Generator™
This is the safest and best way to control pH in all marine aquariums. This uniform sized powder dissolves completely and quickly as it automatically adjusts and maintains pH to 8.3. Even from tanks that have a pH from pH 7.0 to pH 10. It is formulated with several types of carbonates. It will control dKH without using potentially harmful borate or boron. It also adds essential calcium.

Preliminary investigation reveals that the presence of borate can have detrimental effects on select delicate captive ocean animals in closed marine aquariums. Like phosphate and silicates, it appears beneficial to omit borate in synthetic sea salts.

Qualified researchers and knowledgeable marine aquarists understand the many benefits of the superior approach to pH stabilization and control. They understand this is best accomplished by utilizing various forms of carbonates. E.G. Today’s pH buffering platform. This eliminates possible borate related problems, in the closed marine aquarium.

The S-15™ Report™ indicates that many brands of marine salts contain similar or significantly higher amounts of borate Vs. natural seawater.

In order of concentration BIO-SEA® contains 0.23 ppm. Coral Marine™ (1) contains 0.23 ppm. Marine Environment® contains 0.24 ppm. Tropic Marin® has 4.21 ppm. Forty Fathoms®/Crystal Sea™ has 5.88 ppm. Instant Ocean® has 6.05 ppm. Reef Crystals® has 7.44 ppm. Kent Marine™ (1) has 7.44 ppm. and Coralife® has 9.45 ppm. of B (Borate or Boron).

There are several brands of powdered “buffers” offered to reef and marine fish keepers. One brand (SeaChem™) contains tetra-sodium borate (borax like hand cleaner). This is evidenced by packaging claims and varying amounts of bead like ingredients in the product.

(1) Tested separately from the S-15™ Report™.