A 20 gal long aquarium is one of the most versatile and popular tank sizes for both beginner and experienced fish keepers. With its extended length and moderate water capacity, it offers a perfect balance between space, aesthetics, and ease of maintenance. Whether you’re setting up a freshwater community tank, a planted aquascape, or even a species-specific habitat, a 20 gal long aquarium provides ample room for creativity.
In this guide, we’ll explore everything you need to know about a 20 gal long aquarium in 2025, including installation requirements, ideal fish choices, essential equipment, and the estimated cost of setting up and maintaining one.
Why Choose a 20 Gal Long Aquarium?
This aquarium has dimensions of approximately 30 inches in length, 12 inches in width, and 12 inches in height. This longer, shallower design makes it an excellent choice for fish that prefer more horizontal swimming space rather than vertical depth.
Benefits of a 20 Gal Long Aquarium:
- More Swimming Room – The extended length provides a more natural environment for active fish.
- Easier Maintenance – With 20 gallons of water, the tank is manageable in terms of cleaning and water changes.
- Ideal for Aquascaping – The shallow height allows better light penetration for plants.
- Great for Beginners and Experts – It’s a step up from nano tanks but still easy to maintain.
- Perfect for Small Spaces – It provides a decent water volume without taking up too much vertical space.
Now that we understand why a 20 gal long aquarium is an excellent choice, let’s dive into how to set one up properly.
Installation Requirements for a 20 Gal Long Aquarium
Setting up this aquarium involves more than just filling it with water and adding fish. You need the right equipment and careful planning to ensure a stable and healthy aquatic environment.
1. Aquarium Stand or Surface
A 20 gal long aquarium weighs around 225-250 lbs when filled with water, substrate, and decorations. Ensure you place it on a sturdy stand or surface that can handle this weight. A dedicated aquarium stand is ideal, but a reinforced table or counter can also work if it’s level and stable.
2. Filtration System
A reliable filter is crucial to maintaining water quality. Since a 20 gal long aquarium has a large surface area, a hang-on-back (HOB) filter or a canister filter works best. These filters provide excellent mechanical, biological, and chemical filtration. Recommended options include:
- AquaClear 50 HOB Filter – Best for easy maintenance and powerful filtration.
- Fluval 107 Canister Filter – Ideal for a quieter, external filtration system.
3. Substrate and Decorations
The type of substrate depends on your setup:
- Gravel – Best for general freshwater tanks.
- Sand – Ideal for bottom-dwelling fish like corydoras.
- Soil-based substrate – Necessary for heavily planted aquariums.
Adding driftwood, rocks, and caves creates hiding spots and natural aesthetics. Always rinse decorations before placing them in your 20 gal long aquarium.
4. Heating and Temperature Control
If you plan to keep tropical fish, you’ll need a heater to maintain water temperature between 74-80°F. A 100-watt adjustable heater works well for a 20 gal long aquarium. Recommended heaters include:
- Eheim Jager 100W Heater – Reliable and durable.
- Fluval E100 Advanced Heater – Precise temperature control.
5. Lighting System
Lighting is essential for fish and plant health. For a 20 gal long aquarium, an LED light designed for freshwater tanks is recommended. Some great choices in 2025 include:
- NICREW ClassicLED Plus – Affordable and effective.
- Fluval Plant 3.0 LED – Best for planted aquariums.
6. Water Conditioner and Test Kits
To keep your 20 gal long aquarium safe for fish, use a water conditioner like Seachem Prime to neutralize chlorine. Regularly test water parameters using an API Master Test Kit to monitor pH, ammonia, nitrite, and nitrate levels.
Ideal Fish for a 20 Gal Long Aquarium
A 20 gal long aquarium allows for a diverse range of fish species. Since it offers more horizontal swimming space, many small to medium-sized fish thrive in this setup.
Top Fish Choices for a 20 Gal Long Aquarium
Community Tank Options
- Neon Tetras (10-12 fish) – Small, vibrant, and peaceful.
- Guppies (6-8 fish) – Hardy and colorful.
- Platies (4-6 fish) – Active and easy to care for.
- Corydoras Catfish (6 fish) – Great bottom dwellers.
- Honey Gourami (1-2 fish) – Peaceful centerpiece fish.
Single-Species Tank Options
- Dwarf Cichlids (Apistogramma) – Beautiful and interactive.
- Pea Puffers (3-4 fish) – Small but require careful tankmate selection.
- Betta Fish (1 male, or a female sorority of 4-5) – Vibrant and easy to care for.
Planted Tank Fish
- Ember Tetras – Bright orange schooling fish.
- Otocinclus Catfish – Great algae eaters.
- Kuhli Loaches – Active bottom dwellers.
Fish to Avoid in a 20 Gal Long Aquarium
- Goldfish (require larger tanks)
- Large cichlids (too aggressive or territorial)
- Plecos (grow too big for a 20-gallon tank)
Approximate Cost of a 20 Gal Long Aquarium Setup
Setting up a 20 gal long aquarium requires an initial investment. Here’s a rough breakdown of the costs in 2025:
| Item | Approx Estimated Cost |
|---|---|
| 20 Gal Long Aquarium | $50 – $80 |
| Aquarium Stand | $70 – $150 |
| Filtration System | $30 – $100 |
| Heater | $20 – $40 |
| Lighting System | $30 – $80 |
| Substrate & Decorations | $40 – $100 |
| Water Conditioner & Test Kit | $25 – $50 |
| Fish & Plants | $50 – $100 |
| Total Estimated Cost | $300 – $700 |
While the 20 gal long aquarium setup may seem costly upfront, it provides long-term enjoyment and a rewarding fishkeeping experience.
Note above mentioned cost is approx cost, final cost may vary shop to shop and location to location.
Tips for Maintaining a 20 Gal Long Aquarium
To keep your 20 gal long aquarium thriving, follow these maintenance tips:
- Perform 20-30% water changes weekly to maintain water quality.
- Clean filter media monthly (rinse in tank water, not tap water).
- Monitor fish health and look for signs of illness.
- Check water parameters weekly using a test kit.
- Avoid overstocking to prevent water quality issues.
Final Thoughts
A 20 gal long aquarium is a fantastic choice for anyone looking to start or expand their fishkeeping hobby in 2025. Its unique dimensions allow for a variety of fish species, beautiful aquascaping, and easy maintenance. By selecting the right equipment, setting up the tank properly, and maintaining it regularly, you can create a thriving aquatic environment that lasts for years.
Whether you’re a beginner or an experienced aquarist, a 20 gal long aquarium offers endless possibilities for creativity and enjoyment. Are you ready to start your aquarium journey? Let us know how you plan to set up your 20 gal long aquarium!