What Are Coral Frags?

What Is A Coral Frag? A Beginner’s Guide to Coral Fragmentation

The terminology used in marine aquaria can get confusing quickly. If you don’t know anything about the processes used to propagate coral or the ways in which they grow, you probably find yourself asking “what are coral frags?” 

Coral Frag Definition: a coral frag is a small piece of coral containing one or more polyps that can grow into a new coral colony.

Coral frag is short for “coral fragment”, which is just a small piece of coral containing one or more polyps that can grow into a new colony. Corals are generally colonial animals composed of many polyps that are nearly identical from a genetic standpoint, and this shared identity is part of how they multiply and “frag”. Coral frags are created in several main ways, including cutting, splitting, and natural breaks.

Splitting can be beneficial for specific corals for the simple reason that it works with the coral’s natural growth patterns. Certain kinds of coral like zoanthids spread through a connected tissue mat that can be divided along natural growth lines. Splitting the colony along naturally weak growth lines allows for a clean division tied to the coral’s skeletal or tissue structure. This technique ultimately focuses on working with the coral’s natural growth as opposed to determining cut points freehand. When done correctly with the right kinds of coral, this method can often lead to faster healing than would aggressive cutting.

Environmental breaks occur when elements of the coral’s environment cause a section of the colony to separate from the main body. In the wild, storms can cause shifts in current that break sections, and animals can bump into skeletons and break pieces off. Because of the inherent variance in the causes and patterns of natural breaks, this type of propagation is less consistent in terms of healing time. Corals that self frag often heal very quickly as this was an entirely natural process initiated by the coral. Some natural breaks also heal quickly if they occurred at a place of natural division in the colony, while other natural breaks may take significantly longer to heal if the coral experienced trauma as a result of the break.

Fragging in Modern Reefing

Some of these processes for coral propagation sound a little bit harsh on the corals, but understanding how corals grow makes it easier to understand why these methods have become the norm. Corals have evolved to be both hardy and fragile. Corals demonstrate fragility in their sensitivity to unstable parameters and nutrient swings, but they demonstrate resilience through their regenerative properties. Corals can incur notable damage or trauma to their skeletons or polyps and still go on to make a full recovery if their environmental conditions are stable. Because of the general lack of mobility of corals, this collection of invertebrates has developed unique strategies for surviving the changing waters of the ocean floor. The ability to regenerate identical tissue after taking damage that would be catastrophic to other animals is paramount among these. Because of this property, reefers can use their knowledge of corals to work with their existing growth patterns and processes to help each unique coral propagate in the most effective way. Cutting, splitting, and natural fragging all play important roles in the ecosystem of coral propagation, both in the wild and in human-made environments. Understanding each method is the first step to effectively propagating coral in a healthy way.

Many reefers prefer to use coral frags rather than more mature colonies for a few reasons. For one, there are cost advantages. Large healthy colonies typically cost much more than individual frags of the same colony because of the growth potential and resilience associated with a larger colony. Coral frags are also much easier to place in display tanks and will “grow into” their surroundings. Mature coral colonies can present difficulties in finding appropriate room to accommodate their future growth, or even to appropriately house their current size around other livestock. Coral frags also present a lower risk during acclimation, meaning that less coral is risked during the transition phase when using small frags compared to larger colonies. In addition, frags often adapt well to captive systems because they grow into the conditions of the tank, so the process is much more repeatable for smaller colonies. All of these factors contribute to coral frags providing more sustainable options for reef keeping than those offered by mature colonies.

The Two Main Categories of Coral Frags

The next main subject related to the question “what are coral frags?” focuses on the corals themselves. There are two primary categories of corals: soft and stony. As their names imply, the main difference between these two kinds of corals is their structure, namely whether or not they have a skeleton.

Best Substrates for Soft Coral Frags

The most important substrate qualities for soft corals are surface texture and stability. The best substrates for soft corals offer surfaces with rough texture and stable placement that allow for easy attachment and encrustation. Because soft corals grow by encrusting outward and spreading mats or tissue across the surface, the surface of the substrate needs to be solid and easy to adhere to. Smooth surfaces or surfaces with large gaps or crevices require the coral to produce extra tissue to bridge gaps or attach securely to surfaces, slowing growth rate. Unstable surfaces that change with flow discourage attachment, and the polyps usually drift to other surfaces.

Best Mounting Options for Soft Coral Frags

The growth process for soft corals also affects the methodology used for mounting them to substrates as well. The mucus and tissue that soft corals deposit to attach to surfaces are often extremely viscous, and effectively lubricate the surface of the coral. Glue is often less effective for soft corals because their mucus-coated tissue prevents strong adhesion. Because of this, we have to rely on more natural processes to attach soft corals to substrates. Many reefers place small reef rocks, frag discs, or frag tiles in an acclimation box with low flow to allow the soft coral frag(s) to attach to the substrate naturally. Frag discs are consistent but less organic than frag tiles, which are highly modular. Frag rubble, typically consisting of loose reef rocks, is the most organic, but offers the least consistency from substrate to substrate. When opting to use reef frag plugs, it’s generally preferable to use plugs with easily removable stems. Overall, the best frag substrates for soft corals typically have high stability, rich texture, and promote natural attachment rather than manual mounting.

What Are Stony Coral Frags?

Stony coral frags require a slightly different strategy for successful mounting. Stony corals grow by depositing a calcium carbonate skeleton, so their structure is extremely rigid compared to soft corals. Stony corals pull calcium ions (Ca²⁺) and bicarbonate/carbonate ions (alkalinity) from the water, which they convert into calcium carbonate. This material is then deposited as aragonite skeleton to form the coral’s skeletal structure. Stony coral skeletons remain permanently attached to the substrate, so the mounting surface is especially important. This growth process consumes a moderate amount of alkalinity, so it’s important to consider when selecting substrates and maintaining water chemistry. Stony corals are further divided into two groups based on skeletal growth patterns, including large polyp stony corals and small polyp stony corals.

Best Mounting Options for LPS Frags

Mounting LPS frags successfully depends on mineral compatibility and substrate stability. One advantage to mounting LPS and SPS corals is that glue can be used in most cases. Although reef-safe glue has trouble sticking to soft corals, the skeletons of stony corals often provide the perfect texture for glue to adhere to. This means that the shape and stability of the substrate are crucial factors for mounting LPS frags. Choosing large diameter plugs or discs with stable bases and lower-profile mounting makes the corals less likely to tip or detach as the colony grows. If you plan to mount your LPS frag before it reaches a few inches in height, then you may find that a frag disc is easiest because you don’t have to remove the stem before permanent placement. However, if you expect that your LPS frag will grow a bit before you permanently place it, then mounting the frag on a plug may be preferable. The best frag plugs for stony corals typically have consistent shape, calcium carbonate based ingredients, and rough surface texture.

What Are SPS Coral Frags?

Small polyp stony coral frags, commonly referred to as SPS frags, usually have thin branching skeletons and require higher light and flow than LPS. Many SPS corals tend to calcify faster than LPS species, which often makes their skeletal growth visible earlier, making their growth visible earlier on average. SPS corals still use calcium carbonate to form aragonite skeletons, so the mineral requirements are quite similar to LPS. 

Best Frag Plugs and Substrates for SPS Corals

In terms of substrates, SPS coral frags are most sensitive to mineral compatibility and surface stability. Frag plugs with narrow stems for rack systems help with coral stability, which is absolutely essential for SPS frags. SPS corals are often mounted first on frag plugs because of their growth patterns, typically grown on a tray or rack before being placed in the display setting. Because of the relatively sensitive nature of many SPS coral frags, elements like substrate mineral compatibility and surface stability become critically important. Minerals like calcium carbonate can help encourage encrustation, while unwanted toxins like leeching alkalinity can cause tissue recession or even damage. Because of this, it’s especially important to use properly cured and prepared substrates when mounting SPS corals. The best frag plugs for SPS corals must have a stable surface with appropriate texture and mineral compatibility.

However, a lot of your decision will depend on other factors like tank placements goals, flow intensity, and long-term growth plans. If you plan to keep your coral on the sandbed during its early stages of encrustation before moving it higher up in the tank, a frag disc may be most appropriate for your coral. If you want to mount a fragile SPS frag that will branch visibly before you mount it in your display, it may be preferable to opt for the stability offered by frag plugs.

Ignoring curing of new plugs

It’s important to understand the makeup and quality of the things you put into your reef tank. Water chemistry and corals are very sensitive, especially in smaller aquariums. Even small frag plugs and other substrates can release toxins if not cured properly before introduction to the ecosystem.

Over-gluing soft corals

Soft corals are very resistant to glues, so it’s not always necessary to use any for mounting soft frags. However, if you do use glue, use it sparingly as a light adhesive framework rather than globbing a dollop and smooshing the coral into it.

Placing SPS on unstable surfaces

SPS coral frags must be handled with care and provided with excellent surface stability to truly flourish. This surface stability includes micro-texture for grip over time, allowing the coral to enjoy moderate flow and rapid skeletal growth. Unstable surfaces cause stress and can lead to tissue recession or polyp loss.

Coral frags offer unmatched accessibility because of the way they grow: there will inherently always be more potential for coral frags than coral colonies, and that’s why they’re used for trading and selling. Coral fragging is also very sustainable, because the process is founded upon the natural growth & reproductive mechanisms of the corals themselves. Coral frags also offer more flexible aquascaping because of their relatively small sizes, which later grow into the terrain around them. And beyond their functionality, coral frags form the foundation of local frag swaps where dealers and hobbyists alike meet to buy, sell, trade, and nerd out about coral of all kinds. This sense of community founded upon coral frags is what got Artisan Frag Plugs into reefing in the first place.