Best Frag Plugs for Coral Growth

Do Your Frag Plugs Support Coral Growth?

Cultivating a miniature reef in the Midwest is no joke. Honestly, cultivating a reef in any environment immediately produces a handful of challenges. From water stability to flow direction to lighting intensity, the variables that go into creating the perfect ecosystem for reef animals are numerous and complicated. And to make matters more delicate, each element you put into the ecosystem—from the sand of the bed to the bacteria in the biofilm to the rocks that form the reef—affects the chemistry of the reef in a small way. 

One of the often overlooked elements of many reef ecosystems is the simple frag plug. Although most of us are well aware of how ugly those little geometric circles look before corals encrust over them, many people don’t realize that frag plug design and material can affect the formation of your reef as well. Composition factors like porosity, material, and curing process mean that even the innocent reef frag plug can have a noticeable impact on your system over time. Whether that impact is good or bad depends entirely on your choice of frag plugs, and choosing the best frag plugs for coral growth means understanding how materials, porosity, and chemistry quietly influence everything happening in your reef.

Ceramic frag plugs are chemically inert, so corals don’t benefit or suffer from using ceramic frag plugs on the mineral level. Ceramic plugs are often scraped or otherwise texturized on the top surface for easier gripping for coral, but the natural porosity is minimal. Ceramic plugs are wonderfully consistent in terms of shape, weight, structure, and ease of cutting off the stems. However, they don’t encourage coral encrustation or blend in with a natural reef setting.

Silica sand can be bound into frag plugs and frag discs that tend to mimic the natural reef setting better than other plugs while offering less structural consistency. Despite common misconceptions, silica itself is not inherently harmful in reef systems when properly bound and cured. Silica sand plugs set the gold standard for porosity and are also chemically inert, so corals and microorganisms alike will be able to easily latch onto the surface. However, silica sand as a material does not encourage coral encrustation like others do, and the composition of silica sand plugs is less consistent than ceramic.

Aragonite-based frag plugs are typically the most beneficial for coral encrustation over time because this mineral is highly present in natural reefs. Aragonite is a calcium-based substance, which means that it helps to naturally buffer elements that are consumed in most healthy reef systems. Although these plugs and discs are often composed of materials that support coral growth, the porosity is often minimal and the geometry typically looks synthetic.

Obviously, each of these material blends approaches coral growth and propagation from a different angle, but how much does it really matter? One thing to bear in mind is that corals, especially stony corals, consume calcium to build and maintain their skeletons. Many species of coral thrive when growing in stable environments on calcium-rich substrates like aragonite or crushed coral. These natural calcium-based materials provide buffering qualities to their ecosystem and serve as nature’s way of recycling past generations to produce stability for the current generation of coral.

Porosity and Coral Encrustation

As stated earlier, frag plug porosity is another big factor in coral encrustation and the development of your microbiome. A smooth surface doesn’t allow for corals to grip and grow properly, while an overly porous surface or pores with dead traps in them can leave room for detritus and other microscopic issues to blossom.

The reason frag plugs are a small but important piece of the reef to consider is because in many cases they never leave the reef. Depending on your personal technique, the kind of coral, and the overall goals you have for your tank, it’s possible that once you remove the stem from the plug and find a proper spot for your frag it will not move again for a long time, if ever. These plugs need to blend in with their environment, and facilitate healthy encrustation while discouraging pest growth. Lack of surface texture can slow down the rate of coral growth because it takes more energy for the coral to do so.

On the other hand, dead traps and macropores can make the perfect breeding grounds for nuisance algae if not regularly cleared out with moderate bursts of flow. The best frag plugs for coral growth find the perfect balance of varied porosity without any hotspots for harmful bacteria.

During the soak stage, the plugs must be fully submerged in water that has been purified in a 4-step reverse osmosis deionization (RODI) system. This process often takes several weeks depending on the types and concentrations of materials used in the plugs. Although no visible changes to the plugs take place during this process, the RODI water allows any additional chemical byproducts from the mixing process to leech out of the plugs into a safe environment. Over the course of many water changes and several weeks, the RODI water slowly has less and less chemicals leeching into it. Once the water is no longer getting visually dirtier after 48 hours, the plugs are ready for chemical testing and quality assurance.

The chemical testing stage ensures that the plugs are not affecting water parameters in ways they are not supposed to. Parameters like pH and alkalinity will be dramatically affected by cement-based plugs that are not properly soaked, so measuring these parameters in the soak water is a necessity. Intense shifts in alkalinity and pH, especially localized spikes from a frag plug, can affect water stability and even damage tissue. To prevent this, the impact the plugs have on fresh RODI water must be measured over the course of several days. By measuring the alkalinity, recorded in dKH, immediately after pouring the water into the soak chamber we produce a control value for the RODI water. If after 72 hours of soaking the water still shows close to baseline RODI levels (≈0 dKH), the plugs have been fully soaked for reef use. In general, manufacturers using binders and other cement-based products should lean on the longer side of soak times, increase frequency of water changes, and be more stringent with alkalinity tests prior to packaging.

Strength and Long-Term Support

One less discussed aspect of plug quality that affects the health of your coral is the material strength and usability. This is a simple concept, but there are a few things that all of the best frag plugs for coral growth include:

• Ease of stem cutting

• Mechanical stability over time

• Preventing breakage and stress

• Predictable break points

Many of these factors are impacted by a mixture of geometry and materials, and they are fairly absolute. If the plugs can’t check all these boxes, they aren’t worth however little they cost. Stems must be easy to cut for most people because most coral frags will eventually be transferred to a display tank. Those who focus on coral propagation or farming may not struggle with this process much, but the rest of us need plugs that will cut or break consistently in predictable ways each time.

The plugs need to remain stable over time, meaning as the colony grows and the system continues to mature the plug does not erode or decay. Additionally, the plugs need to remain strong and unfractured across the surface designed for corals. Some plugs with low structural integrity develop microfractures or visible cracks upon cutting or breaking the stem, which can stress the coral out and lead to more breaks in the future. This also leads into predictable break points, which mean that the plugs crack in predictable ways so as not to harm a mounted frag. The best plugs for coral growth are strong enough to survive general reef life, break as intended, and remain consistent over time.

When selecting frag plugs for your aquarium, here are a few simple questions to help you narrow your choices:

1. Are the plugs made with materials corals like?

2. Do you trust the manufacturer?

3. Will you like seeing the plugs in your aquarium for 6+ months?

4. Could they cause any problems over time?

Many manufacturers choose to focus on two or three aspects of plug quality, which inevitably leads to ongoing discussions about frag plug pros and cons. However, Artisan Frag Plugs is taking a different approach. By combining natural materials like aragonite, sand, and crushed coral, we can produce plugs that mimic the natural substrate corals love. This was our main mission: to create plugs that truly help corals grow—without a catch.

Using geometrically consistent stems and organically porous discs, Reef PlugsTM by Artisan Frag Plugs provide natural reef growth for corals without sacrificing the convenience of stem mounting. On top of that, we cure and soak each plug with rigid quality assurance checks to ensure each plug produces the exact right buffering qualities that make reef systems happy. Now, you can finally stop compromising with the help of Reef Plugs, the best frag plugs for coral growth.

Learn more about how we create the best frag plugs for coral growth.