How to Set Up a Water Filter in a Fish Tank

Setting up a water filter in an aquarium may seem daunting but with the right instructions and care, aquarists of all levels can tackle an installation.

While there can be a lot of specific steps depending on your exact aquatic filter system, let’s have a look at the main step to set up common types of water filters in an aquarium.

Getting the Right Water Filter System

With many types of filter systems for aquariums available, it can be challenging to know which one is right for you. Reverse osmosis and UV sterilisation are some of the most popular methods, but there are more options out there.

Read our guide on What’s the Best Water Filter System for Aquariums for more in-depth guidance.

Setting Up A Reverse Osmosis System for Your Fish Tank

While exact instructions may vary from one type of filter system to another, setting these up will largely rely on the same steps which are connecting to water supply and wastewater line, assembling and connecting the system and flushing the system before use.

In this guide we’ll detail how to set up a reverse osmosis filter system for an aquarium. Whether your system is a 3, 4 or 5 step one, installation should be very similar. Be sure to always refer to manufacturer instructions to check for any specific set-up requirements.

Step 1: Inspecting the System and Parts

When you unbox your filter system, check that it comes with all the necessary accessories and that nothing stands out of the ordinary. In the unlikely event that your filter has been damaged during transport or else, you want to notice it straight away before using it. It is always good to familiarise yourself with all parts of the set up at this stage and to understand what each one does.

Step 2: Choose Where to Place Your System

You may want to set up your water filter near your aquarium or near a sink, depending on your plumbing and space available. Whichever you choose, you will need to ensure the system has access to a steady supply of cold water and a drain for the wastewater created by the system.

In the event that you are wall mounting your filter system, you may do so at this stage and secure it with brackets or screws. Bare in mind that those may not come with the system you are purchasing.

Step 3: Connecting to Cold Water Supply & Wastewater Drainage

Please Note: It is important to ensure that you have at least 40PSI (3BAR) water pressure before installing a Reverse Osmosis System, as this is the minimum pressure requirement for a Reverse Osmosis membrane to produce RO water. Checking this before installing or purchasing the system allows you to make an informed decision on whether you need to buy a system with a booster pump to help you achieve this pressure, or return the unpumped unit for a pumped unit, which will save you time and money.

Make sure the water supply to your sink is cut off before you start. Following exact instructions that are provided by the manufacturer, you typically will have to cut into an existing copper pipe and install an isolation valve, which usually has to be assembled with fittings provided. You can also use the provided ¾” garden tap adaptor should you have sufficient water pressure from your garden tap.

The ‘male’ part of the fitting should then be screwed on before pushing the pipe on both sides of the isolation valve. Check everything is secured in place before moving on.

For the drainage part, most systems will come with a drain clamp to secure the wastewater line in place. The drain should be installed above the sink trap, as low as possible to limit noise.

Step 4: Assembling & Connecting the System

It’s time to assemble your aquarium filter system. At this stage, the membrane should be left out and housing should be connected to the systems and tightened using a spanner.

Check how long the tube connecting your system and RO system should be and connect tubing to your water supply, drainage and water output line. Colour-coding is usually used to signal which part should be connected to what line, so double-check with manufacturers instructions as the colours could vary.

Remember to remove any collet clips before securing the tubing and check that everything is suitable tightened.

Step 5: Flushing the System Before Use

Thoroughly flushing the system is essential to make sure the system performs optimally and remove any elements from the manufacturing process that may be present in the pre and post filters.

The first flush should be done before the membrane is added to the unit. This is so loose carbon fines or other filter debris doesn’t run into the membrane and cause a potential premature blockage, due to the holes in the membrane being so small.

Turn the water supply on and let the water run for around 10 minutes or until the water seems clear. Any sputtering at this point simply means that trapped air is getting released. Once the water supply is turned back off, let the remaining water drain out. This is also a good time to check for any leaks in your system and make sure everything has been installed correctly.

Next, insert the RO membrane and proceed to a second flush. Proceed in the same way, running the water until at least 10 to 15 minutes. If your system has a L1 or flush valve, open this valve to allow water to quickly flow across the membrane which will speed up the saturation process. Do not use any of the water in your aquarium at this stage. It may be collected in a bucket or storage tank and disposed of. Ensure you close the L1/flush valve once you have finished flushing the system so water can be forced through the flow restrictor which in turn creates the backlog of pressure in the membrane housing which is required to force the water through the membrane to remove contaminants.

The system is now ready!

Maintenance of Your Filter System

Now that your aquarium filter system is installed, you may have to replace membranes, housings and any filter media on a regular basis, typically every 6-12 months depending on your water quality. Keep monitoring your water and your fish to ensure continued water quality and make sure you replace any parts of the system in time.

Interested in reading more?

If you are diving into reverse osmosis, we have plenty of guides including How RO works, How effective RO is or How to Clean an RO System.