Planted Aquaria

Florin pH-

Decreases pH in all Freshwater, Planted, and Marine Aquaria


  • Safely decreases pH in freshwater community and planted aquaria. May also be used in marine aquaria.
  • Gradually decreases alkalinity (“carbonate hardness”) of tap water and aquarium water.
  • Useful for decreasing pH of aquarium water when establishing acidic water conditions in biotope aquaria, simulating the onset of rainy seasons, or for encouraging spawning in fish species indigenous to low-pH environments.
  • Contains no phosphate-based buffers; will not contribute phosphate or nitrogen-based nutrients to aquarium water.


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

Technical Background

Water chemistry requirements of many freshwater fish and motile invertebrate species of interest dictate that the pH of the aquarium water be maintained below 7.0 (e.g. acidic); this is particularly true of aquatic organisms endemic to forested regions with mineral-deficient waters, exemplified by many streams and rivers in South and Central America, West Africa, Southeast Asia, and parts of Australasia. The challenge facing many aquarists wishing to maintain these species in captivity pertains to adjusting pH to the proper range when the water being employed for water changes is rich in dissolved minerals (particularly those that increase alkalinity, such as calcium carbonate) and/or when a reactive aquarium substrate, such as dolomite or calcite, is employed. The best first step is to use only purified water, reconstituted with a suitable remineralizing salt to the desired TDS, when performing water changes (non-remineralized purified water should be used when replacing evaporation); additionally, non-reactive (e.g. inert) bottom substrate should be employed. Having enacted these changes, however, pH may still be higher than the desired level. Use of Florin pH- as directed will result in a gradual, safe decrease in pH. Changes to pH should always be made very gradually to avoid stress of aquarium inhabitants, and a reputable reference source for water chemistry requirements of the inhabitants should be reviewed prior to making any pH changes. Alkalinity (carbonate hardness) should be monitored and adjusted as necessary. Florin pH- is safe for all freshwater aquaria, including those housing plants and motile freshwater invertebrates (e.g. shrimp and other crustaceans, snails and other mollusks, etc.).

Instructions and Guidelines

Do not add Florin pH- to an aquarium without first determining pH and alkalinity with an accurate meter or test kit. Shake bottle before each use. Read entire instructions before proceeding.

Aquarium addition: Add up to 1 ml Florin pH- per 10 US-gallons (37.9 L) in system every two hours until pH has decreased and stabilized at or near the desired level; note that the rate of water circulation in the aquarium will impact the speed with which the active ingredients alter the pH of the system (faster circulation will decrease the time required for pH to change), and that pH stabilization may take up to 24 hours in extreme cases (it is far more likely to stabilize in less than 2 hours, however). Do not enact changes in pH of greater than 0.1 per 30 minutes. As Florin pH- is added to the system, alkalinity will decrease, causing pH to become less-stable and eventually decrease, also. In alkaline water conditions, it is common for pH to decrease temporarily and then increase slightly following addition of Florin pH-; this is simply due to interaction between the active components and the buffering molecules present in the water, and will gradually lessen as alkalinity decreases. At that point, pH will change easily with addition of Florin pH-, therefore proper caution should be exercised to ensure that pH does not drop below a safe level. Consult a reputable reference for alkalinity and pH requirements of the organisms being housed in the aquarium and make adjustments to these parameters as necessary to attain the desired values. Alkalinity may be increased through the use of a buffer (such as Brightwell Aquatics Florin Delta KH+); this will stabilize, and potentially slightly increase, pH.

Tap and/or purified water addition: Adjust alkalinity of water to desired value with a buffer (such as Brightwell Aquatics Florin Delta KH+); once alkalinity has stabilized, add Florin pH- until desired pH is attained. Finally, adjust TDS of water (such as with Brightwell Aquatics Remineralīz or Remineralīz-P, or with Florin Delta GH+ for planted aquaria) to desired value. When water temperature is approximately equivalent to that of aquarium water, add water to the aquarium.

Caution: Contains buffered sulfuric acid; contents may be corrosive and/or irritating. Do not breathe fumes. Keep out of reach of children. Not for human consumption. First Aid: If swallowed: rinse mouth, give water or milk. Do not induce vomiting. In the event of eye or skin contact, flush with water for at least 15 minutes. Contact a physician immediately.


USP-grade Sulfate salts.