What Is Chemi-Pure?

Boyd’s Chemi-Pure is a type of activated carbon combined with ion-exchange resins.

Chemi-Pure is an excellent filtration media for saltwater aquariums and reef tanks. Ordinary activated carbon is known to irritate some corals, causing polyps to close, especially when a large amount is used. Chemi-Pure does not seem to impact corals, even when a fresh unit is placed into the aquarium.

According to the manufacturer Boyd Enterprises, Chemi-Pure removes dissolved organics, phenols and copper and adsorbs ammonia and nitrates, while preventing ion-antagonism in the water, promoting the appetites and well-being of fish.

While Chemi-Pure’s exact formulation is unknown, a similar combination of activated carbon and ion-exchange resins is used in the air-purifying systems aboard submarines!

How Much Chemi-Pure To Use

The manufacturer’s recommendations are:

  • 1 unit (10 oz.) for 5 to 40 gallons
  • 2 units (20 oz.) for 40 to 100 gallons
  • For aquariums above 100 gallons, add 1 unit for every additional 25 gallons

Chemi-Pure is also available in 1/2 unit sizes of 5 oz. each — great for nano aquariums and for fitting into the media compartment of a small hang-on-back filter.  Aquaclear power filters have ample media compartments to place Chemipure.

Chemi-Pure Placement

It is recommended that Chemi-Pure be used in the nylon-mesh bag it comes in, although there is the possibility of using the contents alone in a fluidised reactor, which will probably be more trouble than its worth.

Chemi-Pure works well when placed in the sump in an area of high flow. Place it after the protein skimmer so that it acts on the cleaner water coming out of the skimmer. To prevent detritus build-up that might reduce its efficacy, the bag of Chemipure can be placed between layers of filter wool.

If a sump is not available, Chemi-Pure can be placed into one of the compartments of a hang-on-back (HOB) filter or placed in a canister filter between layers of filter wool.

Using Chemi-Pure Together With Activated Carbon

It is certainly possible to use Chemipure together with activated carbon.

Place a small amount (approximately 4 tablespoons for every 100 gallons of aquarium water) of activated carbon in a mesh-bag in the same compartment of your sump or hang-on-back filter together with Chemi-Pure.  Change out the activated carbon weekly.  The small amount of activated carbon gives a final polish to the water.

Chemi-Pure Maintenance

According to the manufacturer Chemi-Pure has an extremely long useful life in the aquarium, with replacement recommended only every 4 to 6 months! Personally, I prefer to use about half the recommended amount of Chemi-Pure, changing it out at 3 month intervals.

It is recommended that Chemi-Pure be rinsed to remove any excess ash, before being placed into the aquarium. Reverse osmosis or de-ionized water is preferred as we do not want the Chemi-Pure to adsorb impurities that might be present in tap water.

When doing a water change, Chemipure can be rinsed in discharged aquarium water instead of tap water.

Chemi-Pure Elite

Boyd’s latest product is Chemi-Pure Elite which combines Chemi-Pure with ferric oxide to eliminate phosphate which promotes the growth of unwanted algae and inhibits the growth of SPS and LPS corals.

Links to more Saltwater Aquarium Filtration pages:


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