How to Choose the Right Filter (Internal vs External)

A Complete Guide by Blessings Aquarium

Choosing the right aquarium filter is one of the most important decisions for any fish keeper. A filter keeps your tank clean, removes waste, supports beneficial bacteria and ensures your fish stay healthy. At Blessings Aquarium, Pune, beginners often ask:

What Does an Aquarium Filter Do?

No matter which filter you choose, every aquarium filter has three main jobs:

• Mechanical Filtration: Removes dirt, poop, uneaten food

• Biological Filtration: Hosts beneficial bacteria that break toxic ammonia

• Chemical Filtration: Removes color, odour and impurities

Now let’s compare Internal vs External Filters in detail.

Internal Filters – Simple, Affordable & Beginner-Friendly

Internal filters are placed inside the tank and are great for small home aquariums.

Why Choose an Internal Filter?

• Very easy to install

• Budget-friendly

• Low electricity consumption

• Ideal for small fish like Guppy, Tetra, Betta, Molly

Best For

• Tanks below 50–100 litres

• Beginners and first-time aquarists

• Light to moderate fish load

Drawbacks

• Takes space inside the tank

• Limited filtration power

• Not suited for large aquariums

Internal filters are perfect for anyone starting a simple, small aquarium.

External Filters – Powerful, Professional & Perfect for Big Tanks

External filters (canister filters) sit outside the aquarium and offer superior filtration quality.

Why Choose an External Filter?

• Multi-stage filtration

• High media capacity

• Excellent water clarity

• Best for large tanks and big fish

• Hidden outside, keeps the tank neat

Best For

• 100+ litre aquariums

• Malawi cichlids, parrot fish, goldfish

• Planted and aquascape tanks

• Heavy bio-load aquariums

Drawbacks

• Higher price

• Needs space below/behind the tank

• Slightly more maintenance

If you want crystal-clear water and professional performance, an external filter is the best choice.

Internal vs External Filter – Quick Comparison

Feature	Internal Filter	External Filter
Installation	Very Easy	Moderate
Price	Budget-Friendly	Higher
Filtration Power	Medium	Very High
Best Tank Size	Small to Medium	Medium to Large
Visibility	Inside Tank	Outside Tank
Maintenance	Very Easy	Moderate

Which One Should You Choose?

Choose an Internal Filter If:

• Your tank is below 100 litres

• You keep small peaceful fish

• You want an affordable, simple option

Choose an External Filter If:

• Your tank is 100 litres or more

• You keep large or messy fish

• You want premium water clarity

• You have a planted or designer aquascape

Blessings Aquarium Recommendation

At Blessings Aquarium, Pune, we guide new fish keepers daily. Our expert suggestion:

• 1–2 ft tanks: Internal filter (Boyu, Sunsun, RS Electricals)

• 3–6 ft tanks: External canister filter (Sunsun HW series, Fluval, Tetra)

This ensures the right balance between performance, budget and fish health.