Seachem Reef Strontium 500 ml.

Reef Strontium is intended to restore and maintain strontium to levels found in natural seawater without affecting pH.
Strontium is utilized in the same manner as calcium and holds a similar importance in maintaining a vigorous level of growth.
Reef Strontium contains 10,000 mg/L of available strontium as a gluconate complex. Gluconate complexation confers several benefits: it increases the bioavailability of the strontium, it provides a rich source of metabolic energy to help maintain peak coral growth, and it inhibits strontium precipitation/alkalinity depletion.
Gluconate contains no nitrogen or phosphorous, thus it is biologically impossible for it to lead to algae growth in a properly maintained reef system.

Directions:
BEGINNER: Use 1 capful (5 mL) per 80 L (20 gallons) twice a week.
ADVANCED: Check strontium level, then follow dosing regimen above until strontium is adjusted to 812 mg/L. Each dose will raise strontium by about 0.6 mg/L. Size or frequency of dose can be adjusted. Thereafter, use as required to maintain strontium.
EXPERT: After determining the strontium consumption rate, set up a continuous drip system. Use the following formula to determine how much to add to your top-off water: m=0.4vs (m=mL of product to add to top off water, v=volume of tank in gallons, s=amount to raise strontium in mg/L). For example, if you want to raise strontium by 2 mg/L in a 50 gallon tank, then you would add 0.4x50x2=40 mL into the top-off water.
HINTS: Use the Reef Status: Strontium test kit to measure strontium.