Whats The Best Aquarium Filter For My Fish Tank?

All aquarium owners know that filtration is essential for keeping fish happy and healthy. Fish tank filters remove noxious chemicals, clean up debris and aerate water, leaving you with a clear, clean tank in which your fish can thrive. Simply put, filtration systems are the most important piece of equipment for your tank, as your fish can’t survive without them!

Since filters are so important, it can be a daunting task to make sure you pick the right one. Before you decide, these are the key areas for you to consider:

  • Types of filtration
  • Types of filters
  • Your filtration needs

View our range of Fish Tank Filters.

Types of filtration 

First, it’s important to understand how filtration actually works. There are three types of filtration and each processes a different type of waste.

  • Mechanical filtration – this removes solid waste, which is any particle or debris, such as uneaten fish food or bits of fish waste. It works by circulating the water through a foam-like material that traps debris.  Mechanical filtration keeps the tank clean and the water aerated.
  • Chemical filtration – this removes dissolved waste, which is made up of organic compounds, such as decaying tissue, and the chemicals left in tap water, such as chlorine. It works by flowing water through carbon or resin that catches the dissolved waste. Chemical filtration prevents discolouration and keeps tanks odour-free and fish-friendly.  
  • Biological filtration – this removes biological waste, specifically the ammonia that fish waste produces. It works by cultivating nitrifying bacteria to convert toxic ammonia into a harmless nitrate. This nitrate can then be removed through chemical filtration, algae absorption or water changes. This is the single most important type of filtration, as without it, the ammonia will rise to dangerous levels.

Types of filters 

Filters can be separated into two main categories – internal and external. Within each category, there are several different types of filters.

What are Internal Filters?

  • Sponge or Air-Powered Filters – the most basic and inexpensive type of filter, they use an air pump to force water through a sponge-like material. These filters are small and produce gentle, effective mechanical and biological filtration. 
  • Undergravel Filters – these filters are placed underneath a layer of gravel, pushing water through the gravel for mechanical filtration and allowing bacteria to grow for biological filtration. They are relatively inexpensive and easy to maintain. 

View our Internal Filter Range.

What are External Filters?

  • Power or Hang-On Filters – the most common filter type for hobbyists, they hang onto the back of the tank, pulling water up through a pump to provide mechanical, chemical and biological filtration. They are reasonably priced and relatively low maintenance.
  • Canister Filters – these powerful pressurised filters sit underneath the tank, and provide mechanical, chemical and biological filtration. On the more expensive and higher maintenance end of the filter spectrum, they offer a more powerful level of filtration suitable for large tanks.
  • Wet/Dry or Trickle Filters – among the most expensive filters, these derive their name from the dual exposure they provide to both water and air. This makes them excellent for biological filtration, and provides mechanical and chemical filtration as well.

View our External Filter Range.

Choosing the best filter for your tank

Now that you know all about the types of filtration and varieties of filters available, you can choose the best filter for your tank. To do this, you should ask yourself the following questions.

What size is your tank?

Depending on the size of your tank, you will need different levels of filtration. Manufacturers give a recommended tank size on every filter, with the flow rate measured by GPH (gallon per hour). The number of fish (i.e. stock level) in your tank should also be considered.

  • Hospital or breeding tanks – Sponge/air-powered filters are most effective. Since these filters have no moving parts in the tank, small fish and newly hatched fry cannot be drawn into the filter, resulting in lower mortality rates. They also provide minimal disturbance to the water, reducing agitation for sick fish.
  • Small tanks (under 30 gallons), with a small number of fish – Internal filters or power filters are most effective. These filters are powerful enough to maintain quality water conditions, yet gentle enough to keep small fish safe. For small tanks, our 700IF+ Internal Filter is ideal, with a fully submersible filtration pump, directional water flow outlet, venture pipe aeration and UV to help control bacterial issues and green water.
  • Large tanks (over 30 gallons), with a large number of fish – Larger tanks need more power to maintain healthy fish, as the fish place a higher strain on the filter. External canister filters or wet/dry filters are perfect for this. These boast efficient operation, easy access, and more customisation options. For large tanks, our 2000 EF+ External Filter is ideal, with three filter media trays, one customisable tray, easy priming, a spray bar for flow distribution and UV to help control bacterial issues and green water. 

What type of fish and tank do you have?

Different types of fish will thrive best in different filtration environments, so it important to know what type of fish you plan on having before you purchase a filter. Fast-moving fish, for example, love filter flow and can handle powerful currents. Slow-moving fish can tire or even die if exposed to constant filter flow and so need more gentle filtration.

Saltwater tanks have special needs as well. Using a power filter that agitates the surface will allow salt to creep onto the hood and lighting system of the tank, requiring additional maintenance. Instead, use a wet/dry or canister filter.

Planted tanks cannot handle air bubbles as they drive off CO2 and starve the plants; this makes under gravel filters and sponge filters bad options. Filters with carbon are also a bad idea, as they will suck up all the plant food. Even power filters can cause damage, disrupting the water surface and reducing CO2 levels. External canister filters will work best for planted tanks.

What is your budget?

Your budget will help to determine which type of filter you purchase. Don’t get caught up in buying the flashiest, fanciest model; consider your tank’s needs first, and then buy the best suitable filter you can afford. Filters range from low priced (£5 – £50) to high priced (£150+), with sponge filters and some power filters at the lower end, and strong external canister filters and wet/dry filters at the high end. 

How much maintenance do you want to do?

For continued effective performance, all filters need regular maintenance to make sure that the moving components are free and clear. However, some filters require more maintenance than others. Low maintenance filters, like sponge filters or power filters, work well for tanks that aren't overstocked or overfed. External canister filters are more effective for a tank with fish that produce more waste, as they are more powerful, but they also need more regular maintenance. Wet/dry filters, while providing some of the best filtration, are the most complex to set-up as they can require special plumbing and weekly filter rinses. The less time you have to dedicate to filter maintenance, the simpler your filter should be. If your tank gets very dirty, opt for a more durable filter.