How to Safely Clean and Maintain an Aquarium

Whether you’ve just purchased a brand new fish tank or you’re an experienced aquarist, navigating how to clean and maintain one can be a daunting task. 

In this article, we’ll take you through everything you need to know about safely cleaning and maintaining an aquarium, to ensure the best possible environment for your fish. 

Read on to discover how to keep your aquarium in pristine condition…

Fish in an aquarium

Why it’s important to clean and maintain your aquarium

If you already own an aquarium, you will know how quickly it can look abandoned if not maintained and cleaned regularly. It doesn’t have to be a long and taxing process, just keep it simple. Little and often is key! 

In addition to the visible changes that indicate it’s time for a little maintenance, you’ll also need to keep an eye out for the hidden problems, that may not be so obvious at first glance. In fact, most aquarium troubles stem from undetected problems. 

From an aesthetic point of view, wiping down the tank glass, cleaning the ornaments, and siphoning the gravel/sand will instantly improve the overall look of the aquarium. But, what these simple maintenance tasks will also do is prevent widespread algae growth and toxic build-up of waste, which will contribute to the harmful ammonia and nitrite levels in the tank. 

Small, weekly, water changes will also help to remove nitrate and replenish oxygen reserves in the water, which your fish will definitely appreciate! 

Factors to consider 

The level of maintenance required for each fish tank will vary on a variety of factors, however, the main elements will remain the same. 

Generally speaking, the basic principles outlined in this blog will suit every tank but there are exceptions that can be made for certain aquariums, depending on particular factors such as:

  • How mature is the fish tank? 
  • What are the stocking levels for your aquarium? 
  • What types of fish do you keep in your tank?
  • Does the fish tank contain freshwater or saltwater? 

Water testing your aquarium 

A new aquarium will be much more unstable, in regards to water quality, especially whilst it's going through the nitrogen cycle. Therefore, water testing should be undertaken on a weekly basis. Compare this to a mature tank system. As long as there are no issues with the fish tank itself, you can normally leave testing to every 2 to 4 weeks. 

Cleaning your aquarium’s filter sponges 

The more heavily stocked a fish tank is, the harder its filter will work. Because of this, the filter sponges will need cleaning regularly as part of your weekly maintenance, in the water you remove from your tank during a water change, or gravel clean

Never wash filter sponges in chlorinated tap water, as this will kill good bacteria colonies living on the sponges, which will effectively reset the aquarium. In heavily stocked tanks, filter sponges will need to be changed more frequently. When they are no longer usable, change out one part of the filter media at a time to ensure that you don’t end up removing all the good bacteria you have cultivated. 

Staying on top of algae growth 

In a saltwater fish tank, the light system is usually a lot stronger. While this is beneficial to coral growth, it can sometimes promote excessive algae growth. To help with this (between water changes) wipe the tank down with an algae sponge or algae magnet to manually remove the algae. If it becomes an ongoing issue, there are many effective aquarium treatments available to help with eliminating the problem once and for all. To browse a wide range of quality aquarium treatments, click here.  

Although unwanted algae growth is a common problem found with saltwater tanks, it can also be a problem found in freshwater tanks too - but usually, it’s not as severe. If you happen to experience an algae growth in your freshwater tank, simply remove the algae from the glass(during water changes) and add a treatment if the problem persists.

Pro tip - it’s important to remember that the algae is not harmful to the fish and not to remove any more water than is necessary! 

Tank cycling 

Every new aquarium will go through a cycle (known as the nitrogen cycle) that generates and stabilises the levels of good bacteria in the filter system. This usually takes approximately 8 weeks to complete, but each system can vary. 

During this time, an aquarium is extremely unstable. So, caution must be taken before adding any new fish, and a water test should be carried out beforehand to ensure that no ammonia or nitrite is currently present in the tank. 

To prevent sudden spikes during the cycle, it’s important to add new fish in small amounts over a period of time. After all, patience is key! And too much too fast can overload your filter system and set you back weeks of progress.

The cycle will start once the first fish have been added to the tank. The purpose of the nitrogen cycle is to establish a population of living bacteria (e.g. beneficial bacteria) within the filter ecosystem. It will be housed most heavily within the biological filter media, but it’ll also live on every surface of the tank including the substrate, ornaments, and plants. 

As part of its life cycle, the beneficial bacteria will break down the waste and convert the ammonia into nitrite, and then into nitrate. Nitrate is used up by live aquatic plants and is also diluted during water changes. 

If the levels of nitrite or ammonia are getting particularly high, you can help stabilise the levels with bottled biological bacteria. This can be added which should speed up the process.

How to cycle your aquarium

You can cycle your aquarium either by using the fish-in or fishless method. We’ll go through each option in more detail below. 

Fish-in cycling 

A ‘fish in’ cycle is the most popular option, as (generally speaking) you’ll be able to keep fish in your aquarium from the beginning. However, it is recommended you start with only 10% - 20% of your total tank capacity, and choose hardy fish that will be able to tolerate the poor conditions created by the nitrogen cycle. We recommend asking in-store if you need further advice or guidance on selecting these types of fish.

Once the fish are in the aquarium, the cycle will begin. feeding a small pinch of food to the fish, once a day, will prevent a sudden water quality crash, and will allow the beneficial bacteria to begin to grow at a steady rate - without putting the fish at risk.

During the cycle, it is important to test the aquarium water regularly. We would recommend every 1-2 weeks to track the levels of ammonia and nitrite to ensure that they don’t go too high. 

If the levels of ammonia and nitrite do start to spike, a small 10% water change can be done (normally not required until at least week 4), and some liquid beneficial bacteria can be added. Remember to treat any new water with tap safe, to remove any chlorine and chloramines from harming the bacterial colonies and fish. 

Once the tank has had stable zero readings for two weeks, you’ll be able to start adding more fish to the tank!

Build up the stocking levels slowly and steadily over a few weeks to months, keeping a close eye on your water quality as you go. We add fish in this way so that the bacteria colonising the filter system can adapt and grow, rather than being overwhelmed by the increase in fish waste. 

Fishless cycling 

A  fishless cycle is completed in a very similar way, but without the addition of fish to the tank until the cycle has finished. 

In order to start cycling, ammonia solution or fish food can be added to the aquarium at regular intervals. Over time, this will convert to nitrite. Testing should be undertaken regularly, and once there is both nitrite and ammonia present in the tank, the nitrogen cycle has begun. 

Once the levels of both ammonia and nitrites have spiked and then fallen, the cycle is complete. 

Then, your next step is to keep an eye on these levels. If they are showing as remaining stable, it’s safe to add fish. And remember, fish should be added in small quantities, with water tests being undertaken before adding any more.  

Whichever way you choose to cycle your new fish tank,  if you have access to an already established system, it usually speeds the process along if you add some of the filter media from that aquarium into your new one. 

The old system will typically have a fully developed and thriving bacterial colony, which can reduce the length of time it takes to go through the nitrogen cycle in the new tank. This is because it can break down the waste at a much faster rate than the new colony, which would only just be starting to develop. 

Cleaning your aquarium 

Cleaning your aquarium and keeping on top of essential maintenance, such as frequent water changes, is one of the most important parts of fish keeping. 

Establishing a good routine early on will prevent any maintenance problems from ever getting out of hand. Not only that, but a consistent routine will also provide a wealth of benefits to your fish, essential for ensuring they’re happy and healthy!  For these reasons, a basic tank cleaning should be undertaken weekly. 

How to complete a basic tank clean

See below for guidance on how to complete a basic tank clean.

  • Make sure you have everything you need (e.g. sponges, gravel cleaner, bucket, etc).
  • Turn off all the electrics to the tank (e.g. the filter, heater system, lighting)
  • Remove the tank lid and any loose debris from the surface of the water. Depending on the tank, you may want to use a net to do this.
  • Wipe down the internal sides of the tank with a sponge, along with any ornaments or surfaces that show signs of algae growth. Stubborn types of algae can be tough to remove, so you may benefit from having access to a top-quality algae blade.
  • Next, you can start to remove some of the water from your aquarium. Collect any waste that’s accumulated in your tank by using a siphon or gravel cleaner, as these tools will significantly help with removing these unwanted particles.
  • Work swiftly, and keep an eye on the amount of water you’re removing (no more than approximately 10-15% of the volume of the tank).
  • Open up the filter and remove the sponges. Clean them in the bucket of water you have just taken from the fish tank.
  • Once you’re satisfied that the sponges are clean, place them back in the filter. We don’t need them to be spotless, but we do want to remove most of the solid waste so water can flow more freely through them!
  • Next, fill the tank back up with fresh, clean, dechlorinated water. Make sure it’s not too cold, as this will change the overall temperature of the tank and may shock the fish. A thermometer can be used in the tank to track the temperature of the water and see if there are any changes.
  • After you’ve finished replenishing the water in your aquarium, you’re ready to turn your equipment back on. Don’t forget to put the lid back on, too!
  • Lastly, wipe down the external sides of the tank with a cloth to remove any watermarks. Then, simply tidy up and put away any equipment that was used. 

      After an aquarium clean, we recommended doing a quick water test, just to make sure that no parameters have been altered. If that is the case, then don’t panic - the correct treatment can be added to correct this quickly. To browse our range of treatments click here. 

      Essential products for cleaning your aquarium

      No matter what kind of aquarium you own, there are four must-have products that every fish keeper should have. 

      • Sponge – this should only be used to clean your aquarium! Do not use old sponges which have been tainted with cleaning chemicals. You can also use an algae scrub for harder-to-reach places.
      • Bucket – any size will do, but bear in mind you will normally be removing 10% of the tank water weekly. So, be sure to invest in a bucket that can hold the volume of water that will be removed, or it’ll likely turn into quite a messy job! It’s best practice to keep the aquarium bucket separate from household chemicals, as this can indirectly cause harm to your fish. 
      • A Syphon and gravel cleanerThese pieces of equipment are essential for water changes They’ll help to easily remove the waste buildup from the substrate, and also control the removal of the water from the tank, reducing the chance of unwanted spillages. 
      • Tap safe and de-chlorinator - these items make tap water safe for fish by neutralising chlorine, chloramine, and undesirable metals found in aquarium water.

       However, for a more thorough, more professional finish extra steps can be taken during a clean which requires additional aquarium cleaning products. These can vary depending on the type of aquarium setup you have, but can be as follows;

      Please note that the above only covers the basic aquarium cleaning equipment that every aquarist should have. For a more thorough and professional cleaning finish, there are certain additional steps you can take. 

      The specific products required will vary depending on your aquarium setup. However, see below for some general guidelines. 

      Aquascape tanks 

      • Plant scissors - curved plant scissors are ideal for trimming overgrown plants that are found in tanks. These are invaluable when it comes to aqua scaping. Don’t forget to use a net or a siphon to remove any loose plant matter while trimming.
      • Dennerle Care Set -  a specialised beginner aqua-scaping aquarium care set. These comprehensive kits include a cleaning sponge, scissors, tweezers, a fine net, and a microfibre cloth.
      • Substrate shovel - helps to easily correct any fallen substrate or rearrange soil. 
      • Net - can be used to remove and collect loose debris and plant matter from the tank. 
      • Plant nutrients - additional nutrients can be added to encourage plant growth, such as liquid nutrition food or nutrition capsules. Simply insert the nutrients into the soil using tweezers. 

      Tropical or cold water tanks

      • Glass cleaner kit – these comprehensive kits contain attachments that make cleaning the corners of the tank much easier.
      • Water optimiser - great for improving water clarity and overall filtration.
      • Biological cleaner - can be added after a water change. A biological cleaner will help with breaking down waste quicker so that the filter can collect the smaller particles between cleans. In other words, it’ll help with preventing gravel, filter media, and impeller from becoming overwhelmed with fish waste. 

      Marine or saltwater tanks

      • All For Reef - great for replenishing and sustaining minerals within the aquarium that may have been lost through water changes.
      • Water change kit – makes refilling tanks so much easier. Simply place the pump in the jerry can (or bucket) and clip the hose into place. No more lifting heavy buckets!
      • Natural strontium – strontium and calcium additives are great for replenishing depleted levels. For the best results, use weekly after water changes if you have corals, and always remember to regularly test water levels to ensure you are adding the correct amount.
      •  Triple buffer pH is critical in marine aquariums. Ensure your water is at the correct alkalinity by testing and using a triple buffer to correct it. 
      • Jerry Can – If you’re cleaning a marine aquarium then you’ll probably be using salted RO water. You will need a Jerry Can to transport this from the shop to your aquarium.
      • TMC Aquarium Easy Water Change Kit - this miniature pump fits neatly inside the neck of a jerry can, making your life easier! Simply insert the pump and watch the new RO water flow into your marine aquarium. Likewise, this can also be used to remove water from the aquarium. 

      How to clean new aquarium decorations

      After some time, you may want to change the decor of the tank to keep things interesting for yourself and your fish. This can easily be done by adding new ornaments and decorations to the aquarium. Alternatively, you could move the ornaments and decorations you already have around, just to mix things up a bit!

      It’s important to note that, when adding any new items to an aquarium, it’s always a good idea to clean them first, even if they are new! Dust particles and other contaminants can get stuck to decorations, which can later cause issues in an aquarium if they aren’t removed beforehand. 

      This is particularly important for items such as rocks or stones, which can cause severe clarity issues if not thoroughly cleaned before being placed in the tank. 

       For this reason, you should always rinse any new decorations in warm water. Use an aquarium sponge to wipe down all sides and any hard-to-reach crevices. Then, simply position the decorative piece in the aquarium, and add some tap safe to the water. 

      Maintaining your aquarium

      Maintenance of an aquarium simply means regularly cleaning and inspecting your tank. By following a consistent cleaning routine and testing your water regularly, you can prevent and identify any sudden changes to your aquarium water. 

      To maintain peak health levels amongst your fish, it is recommended to undertake visual health checks, by watching the fish and checking for:

      • Any changes in behaviour- this could be flicking, signs of lethargy or inactivity, and the inability to control buoyancy.
      • Physical changes to the body- for example, this could be visible fungal infections, changes to their colour, or showing signs of a curved spine. 
      • Damage to fins/body- keep on the lookout for sores, fin rot, mouth rot, and so on.
      • Whitespot- this is when little white spots (visually comparable to salt) appear all over fish. Whitespot is a contagious disease. 

      We wholeheartedly recommend doing some thorough research before committing to any type of fish. 

      After all, the more you know about the species of fish you’re interested in, the better equipped you are to take good care of them. Plus, you’ll be able to identify anything that’s considered ‘abnormal’ for them, allowing you to swiftly react. 

      Any signs of abnormal behaviour should never be left alone, and instead treated appropriately.  When it comes to fish, the key is catching the problem early!

      Essential products for maintaining your aquarium

      No matter what type of aquarium setup you have, there are several essential products that are well worth the investment. Once you’ve mastered cleaning your fish tank, these items are ideal for maintenance, helping to prevent any sudden changes from occurring, which will ultimately keep your fish stable, happy, and healthy. 

      One of the most important elements of this is water testing. By testing the water regularly, you can see what is happening with the water and react accordingly. See below for our top recommended products.  

      NT Labs Aquarium Lab Multi-Test Kit

      The NT Labs Multi Test Kit is a truly fantastic, broad-range test kit that allows you to check pH, ammonia, nitrite, KH & GH levels. 

      This is a must-have for all levels of hobbyists. Testing your water is an essential task when keeping fish and understanding the science behind it will improve your chance of success. This is a suitable test kit for both cold water and tropical setups.

      NT Labs Aquarium Lab Multi-Test Kit - shop now.

      Salifert pH, Nitrite & Ammonia test kits

      Salifert pH, Nitrite & Ammonia test kits are the perfect starter testing kits for marine tanks. 

      Marine fish require a little more attention than their freshwater counterparts. 

      You must learn the basics of keeping marine water, and these tests will help you do that. We recommend testing from day one. 

      For more information, follow the quick links below to find out more information on each Salifert testing kit. 

      • Click here to discover more about the Aquarium Salifert Profi pH Test Kit. 
      • Click here to find out more about the Aquarium Salifert Profi NO2 Nitrite Test Kit.
      • Click here to learn more about the Aquarium Salifert Ammonia NH3 Profi Test Kit.

      Beneficial bacteria 

      It's always a good idea to have some good bacteria on hand in case of an ammonia/nitrite spike. A great option that we would recommend is the Fluval Aquarium Cycle Biological Enhancer, which is available in a range of size options here at Complete Koi. 

      This is because, when you have beneficial bacteria at the ready, you’ll be able to deal with any issues that arise quickly and before the problem gets out of hand, which can cause issues for your fish.  

      Beneficial bacterias are essential while your immature fish tank is going through the nitrogen cycle. The bottled bacteria will help the natural process along and keep your fish happier. It can also be applied routinely and when adding new fish. 

      Fluval Aquarium Cycle Biological Enhancer

      Fluval Aquarium Cycle Biological Enhancer - shop now.


      A pH Buffer and Carbonate Hardness supplement. The overall pH is a critical water parameter in all fish tanks, however, not all fish have the same requirements. Do your research on the fish you want to keep to ensure the water is right for them! 

      For example, Malawi Cichlids like their water alkaline (e.g. pH 8.0 - 8.2) while South American tetras, such as cardinal tetras, prefer their water acidic (pH 4.6 - 6.2). You can easily achieve these water parameters with the addition of buffers and pH water treatments. 

      Our recommendations would be either the Aquarium Aqua Buffer (for tropical cold water tanks) or the Aquarium Tropic Marin Triple Buffer (for marine tanks) additives to increase pH & KH levels if they crash. 

      Algae magnet

      Unkept fish tanks will quickly develop a thick layer of stubborn algae on the glass. So, to remove any build-up from your aquarium, you’ll require a top-quality algae magnet. 

      A build-up of algae will make your aquarium appear unkept and impact your visibility of the aquarium. And, if your aquarium happens to be well stocked, glass cleaning may be required on a daily basis just to avoid this. 

      Algae magnets make the job simple without you having to put your hand in the fish tank, which also reduces the chance of messy spillages. We’d recommend using the Betta Aquarium Floating Magnetic Algae Cleaner available in various sizes to suit all aquariums here at Complete Koi. 

      Betta Aquarium Floating Magnetic Algae Cleaner

      Betta Aquarium Floating Magnetic Algae Cleaner - shop now.

      If you happen to have a marine setup,  it may also be worthwhile investing in the products listed below. 

      • Refractometer/Hydrometer - tests the salinity of the water. Salinity is the most essential water parameter when it comes to keeping marine fish. Keeping a salinity of 1.025 sg (specific gravity) isn’t difficult when you have the right equipment. Use the scale provided on refractometers or hydrometers to determine the salinity of your aquarium. Having the correct salinity will ensure your fish and invertebrates (including corals) will be happy. 
      • Jerry Can - to transport water if you intend to buy it pre-mixed. Jerry cans are robust containers that are essential for those buying RO (reverse osmosis) or salt water. They normally come in 10L, 20L, and 25L variations.
      • Additional testing kits - we’d recommend looking for calcium, phosphate, magnesium, KH, and nitrate kits. Remember, if we keep our water parameters correct, our fish will thrive. Use these simple tests to ensure your marine aquarium water is free of ammonia and nitrite while having a suitable balance of essential minerals.
      • A coral reef test kit – keeps corals healthy as well as fish, ideal for creating a thriving aquarium environment. Corals are more sensitive than fish and will quickly respond to poor water. This simple test kit is ideal when checking your marine water is adequate for corals and other invertebrates. 
      • Marine salt - If the salt levels suddenly drop you will be able to fix this quickly. Marine salt comes packed with reef-safe salt and other essential minerals which will keep your tank mates happy. Use the salt in conjunction with readings from a refractometer/hydrometer to decide whether more (or less) salt is required if your marine fish tank.

       Final advice for keeping your aquarium healthy 

       If you take anything from this article, let it be the following:

      • Invest in a testing kit - you will use it more than you think, and it provides such peace of mind knowing that everything is as it should be. Plus, you’ll be able to rest assured that your fish are living in their optimum environment!
      • Add your fish in small amounts - as tempting as it may be to fill your tank full of all wonderful fish, it isn’t in their best interest. So, always remember to stock your tank slowly, so that you can track any changes to your ecosystem.
      • Don’t overfeed! - for health reasons, it’s not ideal for fish to be overfed. This will also help to prevent excess food from rotting at the bottom of the tank, which is known for having a negative impact on water quality.
      • Do regular water changes – a 10% water change, once a week, is the best course of action for most tanks. It is much better for the fish’s health to do small frequent changes like this than larger changes sporadically.
      • Be patient and take things slowly- one of the hardest things about fish keeping is the patience it requires. For the best results, things need to be taken slowly. So just take your time and don’t rush into anything! 
      • Ask for advice – nowadays, there is so much information readily available, which can make seeking guidance unnecessarily difficult. So, if you feel confused or unsure - ask for help. Feel free to pop into our store or call us, as we’re always happy to help here at Complete Koi. 

      Find everything you need for your aquarium maintenance at Complete Koi

      Here at Complete Koi and Aquatics, we have everything you need to successfully maintain your aquarium. 

      We offer an extensive variety of aquarium products, which are designed to take the hassle out of cleaning and maintaining your aquarium, whilst also ensuring your fish remain happy and healthy. 

      If you follow the advice in this blog, we will guarantee you success, however, if you do have a question please don’t hesitate to reach out to us directly. Click here to get in touch today!

      Shop cleaning & maintenance equipment for your aquarium at Complete Koi today

      For more information and advice on aquatics, check out the rest of our blog…


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