Two Little Fishies CDX is a carbon dioxide (CO₂) adsorption media designed to help raise and stabilize pH in saltwater reef aquariums by removing CO₂ from the air before it enters your protein skimmer.

Key Features

Removes CO₂ from the air supplied to your protein skimmer.
Helps increase and stabilize aquarium pH naturally.
Ideal for reef tanks in homes with elevated indoor CO₂.
Works in a PhosBan Reactor or similar media reactor connected to a protein skimmer.
Color-changing media indicates when replacement is needed (white to pink/violet, depending on the batch).

How to Use

Fill a media reactor with CDX.
Connect the reactor outlet to your protein skimmer’s air intake using the appropriate tubing and adapter.
Replace the media when it changes color, typically every 6–8 weeks on a 50–100 gallon reef aquarium, depending on indoor CO₂ levels.

This product is especially beneficial if your reef tank consistently has a low pH (around 7.7–8.0) despite having proper alkalinity, as excess indoor CO₂ is often the cause.

CDX Two Little Fishes