5 Golden Rules for Cleaning Your Fish Tank

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The process of cleaning a fish tank or aquarium is often greatly misunderstood, yet can have a significant impact not only on the health of your fish but also how easy you find it to look after your aquatic pets. The goal of this article is therefore to offer some simple rules for aquarium cleaning that will make the whole process as simple and efficient as possible.

Partial Changes Work Best

The first, and most critical, point to realize about your fish tank is that it is essentially a “biosphere” – a self-contained habitat where different species interact with one another. The key here is that it is incorrect to think of your aquarium as just containing your pet fish; instead you should be aware of the wealth of bacteria who also live in your fish tank.

These bacteria aren’t just harmless for your fish; they’re actually beneficial. These bacterial colonies help to rid your fish tank of mess such as faeces and uneaten food, making it a safer and more pleasant environment for your fish. Cleaning a fish tank is about more than simply making it look physically clean and shiny; it’s also critical that we clean your aquarium while keeping these rather sensitive bacterial colonies safe.

Next, it is important to realize that fish don’t react very well to changes in water temperature or chemistry. Significant changes can lead to illness or even death in extreme situations. We therefore want to keep your aquarium as clean as possible, but without killing off the bacterial colonies, or by “shocking” your fish with a massive change to the fish tank chemistry.

The easiest way to accomplish this is through regular, small cleans. Rather than emptying out the tank and replacing all the water in one go, instead we change just a percentage of the water each week. This means fewer changes to water temperature and chemistry, and so a better environment for your fish and the bacteria.

Generally speaking aquarists opt to change roughly 20% of the water in their fish tank every week or two. Keeping an eye on aquarium chemistry (see later) will help you to assess how frequently you’ll need to carry out water changes in your tank.

Stay Chemical-Free

Fish are incredibly sensitive animals and many household chemicals can cause them significant problems. You shouldn’t, for example, clean your aquarium décor with washing up liquid or household bleach, then pop them back into the tank. These chemicals will infect the water and could kill your fish.

This is critical. Generally the best idea when keeping fish is therefore to buy new equipment specially for cleaning your aquarium. Your new bucket, sponge etc. will from that point on only be used for your fish. In this way you can be certain they are free of any potentially-harmful household chemicals.

Get the Right Equipment

Fish tanks are heavy, especially when they’re full of water. The chances of you being able to carry your aquarium through the house to tip out some of the water is highly unlikely; and it wouldn’t be very good for your fish even if you could. No, you’re going to want to clean your fish tank “in situ” – and for this you’ll need the right equipment.

There are two implements here that can help more than any other. The first is a magnetic aquarium glass cleaner. This glass cleaner basically consists of two magnets, with a soft felt covering. You attach one magnet to either side of your aquarium glass and can then gently clean any algae off the inside of your aquarium glass without getting your sleeves wet. You just drag the outer magnet around, and of course the inner magnet follows the same course, while the felt gently removes algae without scratching the aquarium glass.

The second piece of equipment is a gravel cleaner. These devices not only help you to siphon off dirty aquarium water into a bucket for disposal, but will also allow you remove detritus that has fallen down among the gravel grains.

Clean Your Filter Media with Care

The bacteria we mentioned earlier on will colonize almost every surface of your aquarium. However possibly the most critical colony of all is the one living in your aquarium filter. The reason is that it is these bacteria that break down much of the harmful chemicals excreted by your fish into far less harmful components. Killing these colonies by mistake can then be disastrous to the health of your fish tank.

When it comes to cleaning aquarium filters, many people simply remove the spongy material from inside the tank and run it under a tap to remove any dirt. Sadly, this cold, chlorinated water can kill all the helpful bacteria present in the filter sponge. A better alternative is to take the bucket of aquarium water you’ve just removed with your gravel cleaner and rinse the filter sponge in this. This warm, de-chlorinated water is far safer for the bacteria and will help them to survive the cleaning process.

Check Your Water Chemistry

There is a constant “chemistry experiment” going on in your fish tank. Bacteria are helping to break down the harmful ammonia secreted by your fish and turn them into less harmful nitrates and nitrites that are removed with regular water changes. Measuring the levels of these chemicals can be a tremendously beneficial exercise, that will not only help to keep your fish happy and healthy but will also be able to tell you whether you’re cleaning out your fish tank often enough.

While it is possible to buy water testing kits from many pet stores, a large number of specialist aquarist shops will actually test your water for free. Simply take in a little sample in a jamjar and let them check your water chemistry. If there are any issues the fish shop will be able to advise you on the best course of action.


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