Aquarium Filters - Size does matter

Filtering the water is something most hobbyists become pretty clued up on over the years. Partly through trial and error and also advice from shopkeepers and other fishkeepers. The right filter is important to the wellbeing of the fish and really helps maintain healthy bacteria and keep nice clear water.

When I first began keeping fish, I used an internal filter which wasn't strong enough for the tank size. I struggled to keep the water clear and I noticed that the surface of the water was not moving much and had developed a film of oily grime.

I added another internal filter which increased the water movement but i was still needing to do huge water changes to keep on top of the nitrate levels. This still didn't solve the oily surface problem either. It wasn't until I discovered external canister filters that i really understood how important the correct filter was.

When I decide to set up a new aquarium, I think of the following:


  1. Species of fish & conditions best suited for fish 
  2. Minimum tank size for the species vs maximum aquarium I can afford
  3. Filter best suited for aquarium size & fish conditions
It is possible to upgrade your filter later but this can be tricky. With any new filter going into an established tank, "seeding" the media is essential to avoid forcing your tank into a new cycle process. When we set up a new tank, its always advised you let the tank run for 6-8 weeks. This allows your filter media to grow a healthy bacteria colony which will break down the waste your fish produce and keep your water at the right perimeters.

When deciding on a new filter, take into account your aquarium volume. At the very minimum, you need a filter that can turn over your water 5 times an hour. For instance, if you have a 200 litre aquarium, your looking for a filter that has a flow rate of 1000 litre per hour or 1000 L/H. This is a very minimum and applies to freshwater set ups only. Marine fish have a minimum of 10 times per hour upwards.

Once you know what your minimum filter size is, you then need to know what your fish will like. We can keep so many different species now days and a common mistake made by may is to house species from fast flowing rivers together with almost stagnant water fish. Although some water perimeters are similar, the flow rate can be the difference between stunning colours or dull stressed out fish.

Spray bars are great are a great way to spread the water
External filters are normally my first choice whenever possible. I like the spray bar outlets for distributing the water and creating good water movement on the surface.

When your have your aquarium up and running, your filter will do a great job of keeping your water clear. It also provides water movement which oxygenates your water too. This is good for your fish. Species like white cloud mountain minnows are used to fast flowing streams so benefit from similar water flow. Fish like Siamese Fighter Fish are more familiar with still water ponds and only require a very small amount of water movement.

Always remember that in order to function correctly, your filter needs regular cleaning. the most valuable piece of advice I was given was to use the aquarium water to rinse out your filter sponges. This can be done once a month during a water change. Keeping health media is also important. This needs cleaned regularly and the sponges/pads replaced from time to time.

Floss, Coarse sponge and ceramic media all aid health water
Never, Never, Never use tap water or cleaning products (like fairy liquid, Andrea Freel)  to clean your filter during maintenance. This will kill all the bacteria and your tank could suffer massively as a result of this common error.

Filters are like the heart of your aquarium. If you look after them, they will work away, pumping clean water around your aquarium for many years. Take them for granted and allow them to get clogged up and you will end up loosing fish and eventually your tank will grind to a halt.

Thanks for reading guys,

Have a great weekend.

 Bye for now




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