Introduction to Frag Tanks: How to Manage Coral Frags and Build a Propagation System
A guide to designing and operating a frag tank system for managing and propagating coral cuttings (frags).
Key Takeaways
A guide to designing and operating a frag tank system for managing and propagating coral cuttings (frags).
Related Species
What is a Frag Tank?
Among marine aquarists, a "frag tank" is essential equipment for coral breeding and distribution. Frag is short for "fragment," referring to coral cuttings. A frag tank is a dedicated aquarium designed to allow cut coral to heal and grow, requiring a design that balances production efficiency with ease of management.
The main purposes are as follows:
- Promoting healing and growth of cut coral
- Centralized management of multiple coral species
- Conditioning coral before sale or distribution
- Quarantine and recovery of diseased or stressed coral
For breeders and coral vendors, frag tanks are a source of revenue, and for hobbyists, they serve as a base for expanding collections and facilitating trades.
System Design Fundamentals
Tank Size and Configuration
Frag tanks prioritize ease of operation, and shallow tanks are the standard. A water depth of 20-30cm and width of 60-120cm allows uniform light distribution and makes work with tweezers and scissors easier. Install circulation pumps with a flow rate of 20-30 times the tank volume per hour, positioning multiple powerheads at different angles to avoid creating dead spots (stagnant areas).
Overflow systems are most advantageous for maintaining stable water quality. By concentrating a protein skimmer and reactor in the sump tank, you keep the main display tank clean while ensuring high processing capacity. Small setups can use hang-on skimmers, but as the number of frags to manage increases, the benefits of converting to an overflow system become more apparent.
Lighting Selection and Placement
High-performance LED lighting is essential for frag tanks. When primarily working with SPS (Acropora species), a PAR (photosynthetically active radiation) of approximately 450-600 μmol/m²/s is recommended; for soft corals and LPS, 100-300 μmol/m²/s is often sufficient. When managing multiple species, utilize dimming functions and vary light intensity across the tank so placement can accommodate different light requirements. Hang lights at a height where light falls uniformly on the central frag rack, minimizing light loss at the edges.
