21 Gallon Rimless Reef Ready Frag Aquarium – Your Perfect Starter Tank

Starting a coral frag tank can feel overwhelming—especially when you’re juggling equipment, plumbing, and aesthetics all at once. You need a system that’s not only ready to go out of the box but also built for the delicate needs of reef life. That’s where the 21 Gallon Rimless Reef Ready Frag Aquarium / Plumbing Kit AM13621 shines. Designed specifically for fragging and growing corals, this all-in-one solution combines sleek design with reef-ready functionality—so you can focus on what matters most: your corals.

What Is the 21 Gallon Rimless Reef Ready Frag Aquarium (AM13621)?

The 21 Gallon Rimless Reef Ready Frag Aquarium (Model AM13621) is a compact, all-in-one nano reef system built for coral propagation (aka “fragging”). Unlike standard aquariums, it comes pre-plumbed with built-in overflow, return lines, and a dedicated sump compartment—eliminating the guesswork of DIY setups. Its rimless design offers a clean, modern look, while the “reef ready” label means it’s engineered to support stable water parameters essential for SPS, LPS, and soft corals.

According to industry experts like Reef Builders, nano frag tanks under 30 gallons have seen a 40% increase in popularity since 2020, driven by urban hobbyists seeking space-efficient, low-maintenance reef systems. The AM13621 fits this trend perfectly.

Why Choose a Rimless Reef-Ready Frag Tank?

Aesthetic & Functional Benefits

• Rimless Design: No plastic trim means unobstructed viewing and better light penetration—critical for photosynthetic corals.
• Built-In Overflow: Eliminates noisy, unreliable hang-on-back filters. Instead, water flows silently into a rear chamber.
• Reef-Ready Plumbing: Pre-installed bulkheads and tubing (typically ¾” PVC) reduce setup errors and leaks.
• Optimized Flow: Engineered for even water circulation, preventing dead zones where detritus accumulates.

💡 Pro Tip: A study published in Coral Reefs Journal (2023) found that tanks with consistent laminar flow showed 22% faster coral growth compared to chaotic flow patterns.

Key Features of the AM13621 Model

This tank does not include a stand, heater, protein skimmer, or lighting—giving you full control over your equipment choices. While this may seem like a drawback, it’s actually a strength: you avoid paying for components you’d replace anyway.

How to Set Up Your AM13621 Frag Tank – Step by Step

Setting up your 21 Gallon Rimless Reef Ready Frag Aquarium is straightforward if you follow these steps:

1. Place on a Level, Sturdy Surface
   Use an aquarium stand rated for at least 200 lbs (water + rock + glass = ~180 lbs). Never place on furniture not designed for aquariums.
2. Rinse All Components
   Wash the tank, plumbing parts, and bulkheads with freshwater (no soap!). Use a soft sponge to avoid micro-scratches.
3. Install Bulkheads & Plumbing
   • Insert ¾” drain bulkhead into the overflow compartment.
   • Connect the return line from your pump to the return bulkhead.
   • Use Teflon tape on threaded fittings to prevent leaks.
4. Add Live Rock & Substrate
   Use 10–15 lbs of cured live rock for biological filtration. Add ½–1” of aragonite sand for natural buffering.
5. Fill with Saltwater
   Mix 5 gallons of RO/DI water with marine salt (e.g., Red Sea Coral Pro) to reach 35 ppt salinity (1.026 SG). Ideal temperature: 76–78°F (24–26°C).
6. Cycle the Tank
   Let the system run for 4–6 weeks before adding corals. Test for ammonia, nitrite, and nitrate weekly. Target: 0 ppm ammonia, 0 ppm nitrite, <10 ppm nitrate.
7. Add Corals Gradually
   Start with hardy soft corals (e.g., zoanthids, mushrooms), then progress to LPS and SPS after 2+ months of stability.

🔗 For more on the nitrogen cycle, see Aquarium Nitrogen Cycle – Wikipedia.

Pros and Cons of the AM13621 Frag Tank

✅ Pros

• Space-efficient: Fits on desks, countertops, or shelves.
• Plug-and-play plumbing: Saves hours of DIY work.
• Excellent for frag trading: Many reef clubs use identical tanks for standardization.
• Low evaporation rate due to tight-fitting rear chamber.

❌ Cons

• No included lighting or skimmer: Requires additional investment (~$150–$300).
• Limited stocking options: Not suitable for fish (except tiny gobies or blennies in some setups).
• Small water volume = less stability; parameters can swing quickly if neglected.

⚠️ Reality Check: Nano reefs demand weekly maintenance. Test water twice weekly, perform 10–15% water changes, and clean the overflow weekly to prevent clogs.

Who Is This Tank Best For?

• Beginner fraggers wanting a low-risk entry into coral propagation.
• Experienced reefers needing a dedicated hospital or quarantine frag tank.
• Apartment dwellers with limited space but big reef dreams.
• Educators or offices seeking a living display that’s manageable and stunning.

It’s not ideal for those wanting a full reef with fish, sharks, or large invertebrates. But for coral-focused systems? It’s nearly perfect.

How Does It Compare to Similar Tanks?

The AM13621 holds its own—offering better value than premium brands while matching core functionality. It’s especially popular among budget-conscious fraggers.

FAQ Section

Q1: Can I keep fish in the 21 Gallon AM13621 tank?

A: Technically yes—but not recommended. The small water volume makes it hard to maintain stable parameters with fish waste. Stick to corals and cleanup crew (e.g., snails, hermit crabs).

Q2: Does the plumbing kit include a return pump?

A: No. The kit includes bulkheads, tubing, and fittings—but you must buy a separate return pump (e.g., Jebao DCS 3000 or EcoTech Vortech MP10 for flow).

Q3: How often should I clean the overflow?

A: Weekly. Hair algae and detritus can clog the overflow teeth. Use a soft toothbrush and vinegar soak for mineral deposits.

Q4: Is this tank suitable for SPS corals?

A: Yes—with proper lighting (e.g., AI Prime 16HD), flow, and stable water chemistry. Many reefers successfully grow acropora in this tank after cycling.

Q5: What size sump works best with the AM13621?

A: A 5–10 gallon sump is ideal. Some users skip the sump entirely and use filter socks + regular water changes—but a sump adds stability.

Q6: Where can I buy replacement parts?

A: Most plumbing parts are standard ¾” PVC, available at hardware stores. For OEM parts, contact the manufacturer (often Aqueon or similar OEM brands under private labels).

Conclusion

The 21 Gallon Rimless Reef Ready Frag Aquarium / Plumbing Kit AM13621 is more than just a tank—it’s a smart, scalable gateway into the rewarding world of coral fragging. With its seamless design, pre-installed plumbing, and nano-friendly footprint, it removes the biggest barriers beginners face while offering enough flexibility for seasoned reefers.

If you’ve been dreaming of growing your own coral garden without the complexity of custom builds, this tank delivers simplicity, reliability, and beauty in one package.

👉 Loved this guide? Share it with a fellow reef keeper on Facebook, Instagram, or Reddit’s r/ReefTank! Your tip could help someone start their first frag tank with confidence. 🌊🐠