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Brightwell Aquatics Kalk+2 - Advanced Kalkwasser Supplement 100g / 3.5oz


Item #: BW01113

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  • Contains calcium, strontium, and magnesium in the same ionic ratios found in aragonite. This unique feature increases the usefulness of Kalk+2 to reef-building invertebrates such as corals, clams, calcareous algae, etc.
  • Provides temporary alkalinity and helps maintain pH within the desired range when used as directed.
  • Adds no conservative elements, such as chloride, to the aquarium.
  • Improves upon the industry-standard powdered calcium supplement over the past three decades.
  • Formulated by a marine scientist.
Technical Background
Calcium, magnesium, and strontium are required for the formation of aragonite, the skeletal material of reef-building invertebrates such as corals, clams, tube worms, and their respective allies. Brightwell Aquatics Kalk+2 provides these elements and may also be used to help regulate pH in reef aquaria. Kalk+2 does not contain chloride salts, which is a strong point for some hobbyists. The use of kalkwasser-type products remains very popular with many seasoned hobbyists, regardless of innovations in calcium-delivery methods.

Instructions and Guidelines
Kalk+2 is intended for use by experienced hobbyists who are familiar with kalkwasser (calcium hydroxide-based) products. The calcium concentration (”[Ca2+]”) and pH in the aquarium should be determined by using an accurate test kit prior to supplementing. Do not add this product directly to an aquarium without diluting in water as directed, and do not overdose; it must be added in a controlled fashion with a dosing device. Create a stock solution by dissolving 6 grams (~1 tsp) of Kalk+2 in 1 US-gallon of fresh water (preferably purified) and allowing at least one hour for any settling to occur; each ml of the saturated sol’n will increase the [Ca2+] in 1 US-gallon (3.785 L) of water by 2.3 ppm, strontium concentration by 0.04 ppm, and magnesium concentration by 0.06 ppm. This solution must then be dosed/dripped into the aquarium at such a rate that salinity does not fall below 1.021 g/cm3 and pH does not increase by more than 0.1 every hour, nor is it ever allowed to exceed a value of 8.5. Dosing at night when pH in a reef aquarium is naturally depressed is often performed to avoid exceeding the maximum allowable pH value. If the [Ca2+] in an aquarium is gradually dropping despite using this product as directed, the rate of evaporation may be insufficient or pH may be too high to dose sufficient calcium to compensate for the rate of removal by reef-building aquarium inhabitants and/or undesirable chemical reactions. In this case, a secondary calcium supplement may be needed to occasionally re-establish the natural seawater concentration of calcium in the aquarium.

Caution: Calcium hydroxide is a caustic material; if inhaled, remove to fresh air, and in case of contact flush skin and/or eyes with fresh water for 15 minutes. Drink 16-oz. fruit juice if swallowed and seek immediate medical attention. Keep out of reach of children. Not for human consumption.

Guaranteed Analysis (by weight)
Calcium (min) 54.20% (542,000 ppm), Strontium (min) 1.00% (10,000 ppm), Magnesium (min) 0.15% (1,500 ppm)
Calcium hydroxide, Strontium hydroxide, Magnesium hydroxide,

Manufacturer information

Brightwell Aquatics Aquarium Supplies
The goal of Brightwell Aquatics is to provide the absolute highest quality, scientifically-sound products and customer service of any aquarium water care manufacturer, and to do it all in a straight-forward and honorable fashion. All Brightwell products are formulated by marine scientists with a passion for the aquarium hobby. They utilize the highest purity ingredients in concentrations that provide the most use to hobbyists. Nearly all Brightwell Aquatics products are over 99.9% pure. The usage guidelines of Brightwell Aquatics products are written in plain language but the company is always available to answer consumer questions. All products are lot numbered for quality control and customer service.

5 Stars


Reviewed on
December 18, 2019

Yes, I would recommend this.

Fast growth!

Pros: Raises pH

Cons: More expensive than other kalkwasser

I’m currently using this on a doser and it helps with keeping my pH up.

Was this review helpful? 0 0


Reviewed on
July 01, 2017

Yes, I would recommend this.

Good stuff

Pros: Dissolves well, can be used to kill aptasia

Cons: None

This is a great kalk supplement. I find that it dissolves more readily than other brands of kalk, which is what could make kalk a pain.
Another awesome, but off label, usage for this is as aptasia killer. You mix water with the kalk, just enough to make a liquidy paste, and you squirt it into the head/mouth of the aptasia and they close up on it and will die.

Was this review helpful? 5 0

josephine clark

Reviewed on
November 19, 2013

Yes, I would recommend this.

Brightwell Aquatics Kalk+2

This product is great. I has caused a bloom in my SPS. I love it. Josie

Was this review helpful? 4 0

david pazer

Reviewed on
February 01, 2012

Yes, I would recommend this.

good product,

make sure you are using enough product. Buy the bigger size....

Was this review helpful? 3 0

josh simmerman

Reviewed on
January 08, 2012

Yes, I would recommend this.

Great Product!

This is a perfect example of getting what you pay for! It is a bit more expensive than others, but it allows for very accurate control!

Was this review helpful? 1 0

joel clark

Reviewed on
November 27, 2011

Yes, I would recommend this.

Hard to Tell Any Difference

This product just looks like expensive lime to me. I tried a jar and it looked and performed like bulk lime. I think it would be really hard to tell if it made any difference.

Was this review helpful? 2 0

benjamin stephens

Reviewed on
March 06, 2010

Yes, I would recommend this.

Nice product

I have been using this product for about 6 months now. Helps maintain my ph and keep my calcium up. It is much easier than other Kalk waters that need to form multiple layers and then be separated.

Was this review helpful? 3 0