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.

Chemi-Pure | What’s In The Bag?

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

chemipure bag

Chemi-Pure’s activated carbon and ion-exchange resin formula

The activated carbon used in regular Chemi-Pure is granulated, like coarse sand. But the secret ingredient seems to be the ion-exchange resin with its orange-red coloration. It looks a lot like DI resin, but nobody other than the good folks at Boyd’s knows what it actually is!

Because Chemi-Pure ships wet, it will have settled during shipping, becoming hard to remove from the jar by just pulling at the nylon bag. And we don’t want to rip that bag by forcibly tugging at it.

When removing the Chemi-Pure from its container, take off the lid and invert the jar. Gently shake the jar upside down a few times until the entire bag falls out on its own.

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

But bear in mind that these amount are just manufacturer’s suggestions. I prefer to just use one 10 oz. bag of Chemi-Pure in my sump at any one time but placed in very high flow as I’ll mention later. Based on my very light fish load, I change out the bag every 2 to 3 months or so.

By the way, Boyd’s also recommends that the media be changed out every 4 to 6 months! Seems like an awfully long time between changes.

Unfortunately, it is impossible to know for sure when the bag of Chemi-Pure has exhausted its usefulness. A lot depends on the condition of your water as well as how the media is placed, so a good rule of thumb would be to change it out more frequently — perhaps once a month — if you have a heavy fish load.

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.

I personally like to place Chemi-Pure in my sump at the chiller’s water output. Flow here is high and it ensures that a good amount of water passes through the medium.

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

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.

Because I use Chemi-Pure in the sump, I usually skip rinsing it altogether. That little bit of ash doesn’t seem to hurt anything.

When doing a water change, and to ensure it is not clogged up with detritus, 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.

Test for phosphates every month or so to check if Chemi-Pure Elite’s phosphate reducing ferric oxide component is still doing its job. Phosphate levels should always be at zero if you have corals!

Chemi-Pure Blue

Released in 2014, and the the very latest in the Boyd range is Chemi-Pure Blue.

Chemi-Pure Blue is being marketed as an a ‘higher-end’ version of the original Chemi-Pure product with its European premium grade pelleted activated carbon and higher grade ion-exchange resin. Also, whereas Chemi-Pure is an all-round carbon product for use in both freshwater and marine systems, Chemi-Pure Blue is specifically formulated for marine and reef aquariums.

Chemi-Pure Blue has less of an impact on trace elements than its predecessors  — an important point when it comes to using activated carbon in the reef aquarium — while removing dissolved organics, copper, metals and phenol. It also keeps, pH stable, raises redox and true to Boyd’s standards, polishes the water to a crystal clear ‘blue-white’. 

And it should be noted that Chemi-Pure Blue is more expensive than both the original Chemi-Pure and Chemi-Pure Elite!

Chemi-Pure Blue is available in 5.5 oz units to treat 35 gallons and 11 oz units to treat 75 gallons. The formulation is, of course, pre-packed and sealed in Boyd’s nylon mesh bags for easy placement in the sump.

Read our Chemi-Pure Blue Review.


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