Common Sense Guide to Filtration in a Goldfish Tank
by Arley Canterbury
 
I have read it many times that goldfish need "10 times water turn over". But what good is water turn over, if the filter cannot handle the waste being produced.  All you will have is a tank with the turbulence of a washing machine, without any cleaning of the water. So let's look at some popular filter types.
 
Sponge Filters
 
Sponge filters are rarely brought up on many goldfish sites today. These filters are powered by an air pump and fit into your tank.
• Inexpensive
• Can be easily put into tank and "seeded" for use in a hospital tank
• Good to Very Good Biological Filtration
• Moderate to Good Debris Filtration

Hang on the Back (HOB) Cartridge Based Filters
 
There are many brands to choice from in this category. These type hang on the back of your tank, and typically have a little cartridge that traps filter and debris.
• Cartridge offers LITTLE Biological Filtration, as the pad is typically no larger than 4" x 6" x .25"
• Carbon within the filter goes bad within a month, typically within a week
• No or little room for Bio-media
• Good to Very Good Debris Filtration
• Moderate to Good Biological Filtration

Hang on the Back (HOB) Cartridge Based Filters with Bio-Wheels
 
There are only two main choices this category, Penguin or Emperor. These type hang on the back of your tank, and typically have a cartridge that traps filter and debris. Depending on the size you purchase, you will have room for additional filtration pads or biological media.
• Cartridge offers LITTLE Biological Filtration, but excellent debris filtration.
• Carbon within the filter goes bad within a month, typically within a week, but can be a source for bio-bugs to grow.
• Room for Bio-media
• Very Good to Excellent Debris Filtration
• Very Good to Excellent Biological Filtration. The Bio-Wheel is an excellent medium for good bio-bug growth.

Hang on the Back (HOB) Power Filters
 
There are only a few brands in this category, with the Hagen Aquaclears being the most common. Although these filters do not have the convenience of cartridge, they offer superior filtration.
• Large Sponge to Trap Waste and Debris, also acts another source of Biological Filtration
• Space to place in Biological Media, such as Ceramic Rings, Cell-Pore Media, Bio-Stars, Bio-Balls, etc.
• Space to add other media such as filter floss, carbon, phosphate filters, etc.
• Very Good to Excellent Biological Filtration
• Very Good to Excellent Debris Filtration

Canister Filters
 
Here is another category that has many brands to choose from. These filters will offer superior filtration over any hang on the back type of filter.
• Large Sponge to Trap Waste and Debris, also acts another source of Biological Filtration
• Large Space to place in Biological Media, such as Ceramic Rings, Cell-Pore Media, Bio-Stars, Bio-Balls, etc.
• Large Space to add other media such as filter floss, carbon, phosphate filters, etc.
• Excellent Biological Filtration
• Excellent Debris Filtration 

So what is the best filter?
 
No single answer, but let’s look at what you will need.
• The filter should be rated for at least DOUBLE the tank size you own, larger if you can afford.
• The filter needs to be able to handle the ammonia levels being produced by the goldfish
• Biological filtration capacity is FAR MORE IMPORTANT than WATER TURN OVER.
• Two filters are better than one.

A good example of filtration for a 55 to 75 gallon goldfish tank

• Two Penguin 350's or Emperor 400's or
• One Penguin 350's or Emperor 400's and a Large Sponge Filter Powered by Air Pump
• Aquaclear with Sponge, Bio-Media, Filter Floss and Carbon and a Large Sponge Filter Powered by Air Pump, or
• Canister Filter and a Large Sponge Filter Powered by Air Pump, or
• Canister Filter and an Aquaclear with Sponge, Bio-Media, Filter Floss and Carbon, or
• Canister Filter and a Penguin 350's or Emperor 400.

Again we need to use common sense when it comes to providing the correct filtration for our goldfish.  As it’s been said many times over, "if we take good care of our water, the water will take good care of our fish".