Filtration can be one of the best ways to help water stay in top quality. Some people will say that goldfish need a water turnover of 10+, but if the filter can't handle that much waste all the occurs is fast moving water, and not much else.

Here are some of the filters available for a goldfish tank.

Sponge Filters

While not mentioned much these days on goldifsh websites, a sponge filter is powered by an airpump and placed inside the tank. Some of the benefits include:

• Cost, they are inexpensive
• Easily place into tank
• Good Biological Filtration
• Moderate Debris Filtration 

Hang on the Back Cartridge Based Filter

This type of filter hangs on the back of your tank and contains a cartridge to trap bedris. Many brands make this type of goldfish tank filter. Some information of the hang on the back cartridge filter include:

• Cartridge offers very little biological filtration
• Carbon within the cartridge can go bad quickly 
• Little room for bio-media 
• Good debris filtration
• Moderate Biological filtration

Hang on the Back Cartridge Based Filters with Bio-Wheels

This filter also hangs on the back of the goldfish tank, and typically has a cartridge that will trap debris. Some filters have room for additional filtration pads, or biological media. The two main choice in these filters are:

• Penguin
• Emperor

Some information regarding Hang on the Back Cartridge Based Filters with Bio-Wheels include:

• Cartridge offers excellent debris filtration, but little biological filtration.
• Carbon the the cartridge can go bad quickly
• Enough room for bio-media 
• Very Good debris filtration
• Very good biologicalfiltration
• Bio-Wheel is excellent for good bacteria growth.

Hang on the Back Power Filters

Although lacking the convenience of a cartridge, power filters offer superior filtration. With several brands making power filters Hagen Aquaclear in by far the most common. 

Some information regarding power filters includes:

• Sponge to trap waste and debris, acts as biological filtration
• Space for biological media
• Space for alternat media, including filter floss, carbon, phosphate filter, etc.
• Very good debris filtration
• Very good biological filtration

Canister Filters

With many brands to choose from canister filters offer superior filtration over any hang on the back filter. Some of the canister filter benefits include:

• Large sponge to trap waste and debris, also acts as biological filtration
• Large space for biological media, including Ceramic Rings, Cell-pore media, bio-stars, bio-balls, etc.
• Excellent Biological filtration
• Excellent Debris filtration

What's the best filter for a goldfish tank?

There is no single answer to this question. There are a few things to keep in mind when purchasing a filter.

• Filter should be rated at double, or more, of the goldfish tank size.
• Filter needs to be able to handle the ammonia levels produced by goldfish.
• Biological filtration is more important that water turn over. 
• Two filters are better than one.

Common sense should come into play wehn choosing a filtration system for your goldfish tank. The water is one of the most important parts to a goldfish's health and welbeing. A filter is the best way to keep your water clean and healthy.