Planted Aquaria


Bioavailable Ferrous & Ferric Iron Source for all Planted Aquaria


  • Provides both ferrous (Fe2+) and ferric (Fe3+) iron sources to maximize benefit to planted aquaria.
  • Two-tiered approach to iron supplementation consists of one ingredient to deliver immediate iron and another ingredient that slowly releases iron during the light cycle, when the aquarium is illuminated.
  • Over 50% stronger than most competing products.
  • Formulated utilizing extensive research on aquatic plant nutrient requirements.


  • 125 ml
  • 250 ml
  • 500 ml
  • 2 l
  • 20 l

Technical Background

Iron is an essential element for plants, both aquatic and terrestrial: it is utilized in the production of chlorophyll and activates some enzymes that take part in metabolic reactions; it does all of this, however, in very small concentrations. Iron is considered a micronutrient, and it is often the limiting element in plant production in some aquatic habitats. This may be demonstrated by observing the increase in plant growth rates that occurs when iron is supplemented in systems in which it was previously immeasurable. Although this increase in plant growth may be desirable, it can be taken too far if iron supplementation exceeds the required concentration; in such an event, it is not uncommon to see increased growth of algae. This is particularly likely to occur in aquaria with excessive concentrations of nitrate and phosphate. As mentioned, iron is also required for the production of chlorophyll, which in turn is required for photosynthesis to occur. A deficiency of iron is physically apparent to the hobbyist as plant leaves which appear yellow or even somewhat transparent. In later stages, the leaves eventually disintegrate under gentle water current or disturbance. While this condition may also be caused by other chemical and environmental factors, it is seemingly most often the result of insufficient available iron (note that K, Mg, and N are also important).

Brightwell Aquatics Florin-Fe delivers iron in two steps: immediate and delayed. This is accomplished through natural biological and photochemical reactions taking place within all aquaria, and results in a more stable iron concentration than is attained with other methods of liquid iron supplementation. It is recommended that iron supplementation be performed on a daily, rather than weekly, basis. Doing so helps maintain a stable iron concentration (in opposition to adding it in large doses) that will enable the element to be taken up gradually by aquarium plants. Additionally, dosing in this fashion will minimize the chance of unwanted algae proliferation that is possible when a “megadose” of iron is delivered to the system all at once, creating a situation in which the iron is, at least temporarily, in a state of gross overabundance. Daily dosing also enables the hobbyist to witness the resultant changes taking place in the aquarium on a smaller time scale, further enabling them to increase or decrease iron dosage as conditions dictate; this is not easy, or perhaps even possible, when dosing once every 7 days, in which case changes may be drastic rather than subtle, and the perceived iron requirements of the aquarium become significantly more difficult to determine.

Instructions and Guidelines

Shake product well before using. The most effective method of using any ion-specific supplement is to determine the ionic concentration in the aquarium prior to supplementing.

Basic: Add 5 ml (1 capful) of product per 50 US-gallons (187.3 L) of aquarium water every other day or as required; this corresponds to 1 ml (~8 drops) per 10 US-gallons (37.9 L). When used in this fashion, 250 ml treats up to 2,500 US-gallons (9,463.5 L). Maintain the iron concentration within a range of 0.05 – 0.10 ppm.

Advanced: Determine the iron concentration in the aquarium using an accurate test kit before supplementing. Each ml of Florin-Fe will increase the concentration of total iron (“[Fe2+/3+]”) in 1 US-gallon (3.785 L) of water by 3.2 ppm. Each drop (250- and 500-ml cap) will increase the [Fe2+/3+] in 1 US-gallon (3.785 L) of water by 0.4 ppm, and the [Fe2+/3+] in 20 US-gallons (75.7 L) by 0.02 ppm. Maintain the iron concentration within a range of 0.05 – 0.10 ppm.

It is advisable to ensure that the concentration of phosphate not exceed 0.05 ppm in the aquarium to be dosed with an iron supplement. If the initial [Fe2+/3+] in the aquarium is below 0.05 ppm, add this product at the maximum rate of 1 ml per 10 US-gallons daily until the desired concentration is attained, then dose daily or weekly as needed (see below). Always attempt to maintain the [Fe2+/3+] within a range of +/-0.02 ppm. To determine the dosing rate of this product once the desired [Fe2+/3+] has been acquired, measure the daily rate of iron uptake (i.e. the decrease in iron) in your aquarium by measuring the aquarium’s [Fe2+/3+] at the same time each day over a one- to two-week period. To determine the daily dosing rate (preferable to weekly dosing) for iron maintenance: estimate the volume of water in the entire aquarium system; divide the daily decrease in [Fe2+/3+] by 3.2; multiply this number by the volume of water in the system to get the daily dosage required (ml) to maintain a stable [Fe2+/3+]. Daily dosing maintains a more stable [Fe2+/3+] (and more natural environment) than dosing weekly, in which the [Fe2+/3+] spikes just after dosing and then gradually decreases throughout the course of the week. See opposite panel for additional important information on this subject.

Caution: Keep out of reach of children. Not for human consumption.

Guaranteed Analysis (minimum)

0-0-0; Iron (Fe) (min) 1.20% (355 mg/oz.; 12,000 ppm)

Sources of Nutrients: Ferrous gluconate, Iron EDTA.

Other Ingredients: Purified water.