Best Frag Tanks & Coral Propagation Gear

A dedicated frag tank changes the way you approach reef keeping. Instead of hoping frags survive in a corner of your display tank, you control the lighting, flow, and spacing needed for healthy coral propagation — and you gain a backup system for recovering from losses in the main tank.

Frag tanks are intentionally shallow. Shallow water means consistent light penetration across the entire growing surface, easier maintenance access, and better flow distribution. Most hobbyist frag tanks range from 10 to 40 gallons with a depth of six to ten inches, though larger commercial-style peninsula tanks exist for serious propagators.

What Makes a Good Frag Tank

The ideal frag tank is rimless, low-iron glass (for clarity), and shallow. Low profile allows a single light to cover the full footprint without intensity falloff at the edges. The tank should be bare-bottom — no substrate means no detritus traps, easier siphoning, and the ability to see coral condition from below (useful for detecting pests).

Popular frag tank sizes include 10-gallon rimless tanks, 20-gallon long tanks, and 40-gallon breeder tanks. The Innovative Marine Nuvo and Waterbox AIO frag tanks are purpose-built options that include filtration chambers. However, many hobbyists simply use a standard shallow tank with an external hang-on-back filter or connect it to their display tank's sump for shared water chemistry.

Lighting for Frag Tanks

Frag tanks need reef-quality light but not necessarily the same fixtures used on display tanks. Because the water is shallow, even modest LED fixtures can provide adequate PAR for growing softies, LPS, and many SPS corals. Budget-friendly reef LEDs like the AI Prime, Nicrew HyperReef, or a compact Kessil pendant work well over standard frag tank footprints.

The key is even light distribution. Frags at the center of the tank and frags at the edges should receive similar PAR levels. A single centered light works for tanks under 24 inches long; wider tanks may need two fixtures or a linear LED bar to avoid dim edges where frag growth stalls.

Flow and Filtration

Gentle, even flow across the frag rack prevents detritus from settling on healing tissue while avoiding the intense current that can dislodge freshly glued frags. A small powerhead or wavemaker set to low-moderate output is usually sufficient. Position it to create a broad, sweeping pattern across the rack rather than a direct jet aimed at individual frags.

If the frag tank runs on its own system (not plumbed to your display sump), filtration should include a basic hang-on-back filter with mechanical filtration, a heater, and ideally a small protein skimmer. If plumbed to the display system, the display's filtration handles water quality and parameters stay matched — the ideal setup for consistency.

Frag Racks, Plugs, and Mounting

Frag racks hold ceramic or plastic frag plugs in an organized grid, keeping frags elevated off the bottom for airflow and easy observation. Magnetic frag racks attach to the glass without drilling and can be repositioned as needed. Egg crate (light diffuser grid) is a budget alternative that works well as a flat frag platform.

Ceramic frag plugs are the standard mounting surface — they accept super glue gel well, provide a stable base, and can be transferred directly to display rockwork once the frag is established. Some hobbyists prefer frag discs (flat ceramic or aragonite pieces) for mushrooms and zoanthids that tend to spread laterally rather than grow upward.

Cutting and Fragging Tools

The essential fragging toolkit includes a sharp pair of coral bone cutters (for branching SPS), a razor blade or sharp scissors (for soft corals), cyanoacrylate gel (super glue gel), two-part marine epoxy, and a container of clean saltwater for rinsing. A Dremel with a diamond wheel or a coral band saw handles larger LPS fragging jobs that require cutting through dense skeleton.

Protective gear matters too. Palytoxin — a potent toxin produced by many zoanthid and palythoa species — is released when these corals are cut, stressed, or handled. Always frag zoanthids in a well-ventilated area, wear eye protection and gloves, and never put your face close to zoanthids being handled. Palytoxin exposure symptoms range from flu-like illness to serious respiratory distress in rare cases.

Temperature and Water Quality

Frag tanks run warm. Shallow water with a light above heats up quickly, especially in summer. A heater with a digital controller keeps temperature stable during cooler months, but a small fan blowing across the surface or a chiller may be necessary in warm climates to prevent overheating. Target the same temperature as your display tank — 76 to 80 degrees Fahrenheit.

Water changes are simpler in frag tanks due to the small volume. Weekly 20 to 30 percent changes maintain pristine water quality and replenish trace elements that growing corals consume. If plumbed to a larger system, the display's water change schedule covers the frag tank automatically.

Starting Your First Frag Tank

Start simple. A shallow 10-gallon rimless tank, a basic reef LED, a small powerhead, a heater, and a magnetic frag rack is all you need for the first system. Stock it with a few frags from your display — leathers, mushrooms, and zoanthids are the most forgiving first fragging candidates. As your technique and confidence grow, expand to LPS and eventually SPS propagation.

The real value of a frag tank extends beyond growing new corals. It serves as an observation station for new acquisitions before they enter the display, a recovery ward for stressed corals, and a trading inventory for local reef club swaps — all from a system that costs less to set up than most display tank equipment upgrades.

Scaling Up: From Hobby to Side Business

Many reef keepers discover that a productive frag tank generates more frags than they can use in their own display. Local reef club swaps, online coral marketplaces, and consignment arrangements with local fish stores all provide outlets for excess production. Some hobbyists scale to multiple frag tanks or larger peninsula-style propagation systems as demand for their corals grows.

Successful coral propagation at any scale depends on water quality consistency, proper lighting intensity matched to the coral types being grown, and patience — frags need time to encrust their plugs, develop strong bases, and grow to a size that is both visually appealing and healthy enough to survive shipping or transport. Rushing frags to market before they are well-established results in higher mortality for the buyer and damages your reputation as a source.

Common Frag Tank Mistakes

The most frequent frag tank mistakes involve lighting and flow imbalances. Too much light on a shallow tank bleaches frags, especially fresh cuts that are already stressed. Start with lower intensity and increase gradually as frags heal and encrust. Too little flow allows detritus to settle on healing tissue, leading to bacterial infections and tissue recession — a leading cause of frag loss in the first two weeks after cutting.

Overcrowding is another common pitfall. Corals in a frag tank still engage in chemical warfare — stinging neighbors with sweeper tentacles, releasing allelopathic compounds, and competing for light and flow. Spacing frags at least two to three inches apart prevents these interactions and gives each piece room to grow without interference. When the rack fills up, it is time to sell, trade, or transfer frags to the display — not squeeze in more plugs.

Neglecting water quality in a standalone frag tank is the third common failure. Small water volumes are less forgiving — evaporation concentrates salinity faster, temperature swings are more dramatic, and nutrient levels spike more easily from a single overfeeding. An auto top-off system, a small heater with a digital controller, and a consistent water change schedule are not optional luxuries in a frag system — they are baseline requirements for keeping frags alive through the vulnerable healing period after cutting.