CaddyStack™ – Modular Filter Tower Extensions & Spare Parts

These CaddyStack™ Modular Filter Tower Extensions are individual replacement and expansion components designed to work with the CaddyStack™ Modular Filter Tower (Filter Sock Replacement Kit).

This product page is intended for reef keepers who already own a CaddyStack™ Starter Kit and want to:

• Replace a specific part

• Add more filtration stages

• Experiment with different media configurations

• BUILD YOUR OWN

👉 New to CaddyStack™?
If you don’t already own a Starter Kit, we strongly recommend starting here:
CaddyStack™ – Modular Filter Tower (Filter Sock Replacement Kit)
(Starter Kits include all core modules needed to build a complete system.)

What These Parts Are For

CaddyStack™ Extensions allow you to customize and fine-tune filtration by adding or swapping individual modules instead of replacing your entire setup.

Each part twist-locks into existing CaddyStack™ towers and is fully compatible within its size category (2.75" / 4" / 7").

These are not standalone filtration systems on their own — they are modular building blocks for your existing CaddyStack™ platform.

Available Sizes

Spare parts are available in the following sizes:

• 2.75"

• 4"

• 7"

Module heights are standardized across all sizes — only the diameter changes to match your filter sock chamber.

Available Modular Components

Mounting Options

Circle Mount

• Designed for traditional round filter sock cutouts

• Used in most sump systems

• Drops directly into the sock opening for even flow

Square Mount (2.75" Only)

• Designed for flat-edge or rear AIO chambers

• Compatible with many AIO tanks such as:

  • UNS AIO

  • Waterbox 10–25

  • Landen

  • Hello Reef

• Dimensions: 2.5" × 2.5" × 2.75" (L × W × H)

4" and 7" systems use circle mounts only.

Short Modules (All are 1" Tall)

Short Cage Module

• Open, high-flow design

• Ideal for quick mechanical filtration or light media use

Short Tube Module

• Solid sidewalls with bottom-only flow

• Forces water downward through floss or media

• Ideal for directing flow and stacking height gradually

Tall Modules (All are 3" Tall)

Tall Cage Module

• Open design allows water to enter and exit from all sides

• Ideal for carbon, biomedia, or high-flow applications

Tall Tube Module

• Solid sidewalls with bottom-only flow

• Extends the water path and forces flow through media

• Ideal for controlled contact time and layered filtration

Tall Cup Module

• Functions like a traditional filter cup

• Simply drop it into your sock holder or filter tray and fill with media

• Compatible with:

  • Filter pads

  • Filter floss

  • Carbon

  • GFO

  • Biological media

• To clean: replace media — no rinsing or washing filter socks

Why Buy Spare Parts Instead of Another Kit?

CaddyStack™ was designed as a long-term filtration platform, not a disposable product.

Spare parts allow you to:

• Replace worn or damaged components

• Add extra towers for higher bioload systems

• Change filtration strategy without rebuying a full kit

• Dial in flow, contact time, and media type over time

Expandable by Design

CaddyStack™ grows with your reef.

You can:

• Stack additional towers

• Mix cage, tube, and cup modules

• Reconfigure filtration as your tank matures

For a complete starting point, visit the
👉 CaddyStack™ Starter Kit product page

Reef-Safe & Built to Last

• Printed in reef-safe PETG

• No raw metal

• No exposed magnets

• Designed for long-term saltwater use

• Rigid construction will not collapse or deform

Important Notes

• These parts are CaddyStack™ extensions only

• A Starter Kit is required to build a complete system

• Media not included

• Designed, manufactured, and shipped by Printed Reef