CDX Carbon Dioxide Adsorption Media — Two Little Fishies (750 mL)
Transform Your Tank with Higher, More Stable pH
Looking for the secret weapon that fixes the low-pH problem most reefers don't even realize they have? CDX Carbon Dioxide Adsorption Media by Two Little Fishies is a clever, science-backed solution stocked at The Coral Boutique for serious reef keepers battling stubbornly low pH from indoor air CO2 buildup. If your reef pH won't climb past 8.0 no matter what you dose, CDX targets the actual cause instead of masking the symptom.
CDX works by scrubbing CO2 out of the air being drawn into your protein skimmer. Closed homes, sealed offices, and tightly insulated buildings concentrate atmospheric CO2 — and every time your skimmer pulls that CO2-rich air through your tank, it drives pH down. Load CDX into a fluidized media reactor (Two Little Fishies' 150 or 550 PhosBan Reactor works perfectly), connect the reactor's outlet to your skimmer's air intake using the CDX Adaptor, and the skimmer instantly becomes a CO2-scrubbing engine. The CO2-free air entering the skimmer pulls dissolved CO2 out of your tank water, allowing pH to rise naturally to its proper range — no kalkwasser slurries, no two-part overdosing, no fragile pH buffering tricks. Best of all, CDX includes a built-in visual exhaustion indicator: the media starts white and turns pink/violet as it depletes, so you always know exactly when to replace it. A 750 mL jar typically lasts 6–8 weeks on a 50–100 gallon reef aquarium.
Key Benefits
- Naturally elevates and stabilizes aquarium pH at its true source
- Scrubs CO2 from skimmer intake air for a CO2-free injection into the water
- Solves chronic low-pH issues caused by closed indoor environments
- No risk of overshooting or crashing pH like with chemical buffers
- Visual color-change indicator (white → pink/violet) signals when to replace
- Works with any fluidized media reactor — pairs perfectly with TLF PhosBan Reactors
- Reef-safe and chemistry-friendly — won't affect alkalinity, calcium, or magnesium
- Ideal for SPS-dominant systems where stable, elevated pH boosts coral growth
Quick Stats & Specs Product Name: CDX Carbon Dioxide Adsorption Media Manufacturer: Two Little Fishies Size: 750 mL Active Function: CO2 adsorption from skimmer intake air Form: Granular media (keep dry — do NOT wet with water) Treats: 50–100 gallons of reef aquarium volume per 750 mL Replacement Interval: Every 6–8 weeks (or when media turns from white to pink/violet) Recommended Setup: Two Little Fishies 150 or 550 PhosBan Reactor (or any fluidized media reactor) + CDX Adaptor Compatibility: Saltwater, reef, and freshwater aquariums running an air-injecting protein skimmer Best For: Reef keepers with persistently low pH (below 8.0–8.1), indoor-located tanks, SPS-dominant systems benefitting from elevated pH Directions: Load CDX into a tall columnar fluidized reactor. Connect the reactor outlet to your skimmer's air intake using the CDX Adaptor or compatible barbed reducing fitting. Keep the supply container tightly sealed when not in use. Do not allow the media to get wet — CDX must stay dry to function.
Why Buy From The Coral Boutique?
At The Coral Boutique, we stock only the equipment and additives we trust on our own systems. CDX is one of those clever-but-overlooked products that solves a real problem for serious reefers — the kind of tool that turns a frustrating, chronic pH issue into a non-issue. If you've been chasing pH stability with no luck, CDX is the upgrade that fixes the cause. Every product on our shelves is tested, vetted, and backed by reefers who actually use it — so you can buy with confidence.
