what is the best way to remove algae from a fish tank

What is the best way to remove algae from a fish tank

Algae is one of those things that hobbyists have differing opinions whether its good or bad. Algae in your fish tank can greatly affect your pH balance that we work so hard to monitor and maintain. It can also block your filters. Conversely, as it produces oxygen it can also have a beneficial impact on your aquarium. The main reason that we tend to worry about algae is it is rather unsightly if left unattended. A little on your decorations can give a slight authentic look but untreated algae can take over your aquarium.

There are chemical solutions available to rid your tank of algae. Many hobbyists will advise against this course of action. The first course of action should be to reduce and prevent algae taking over in the first place.

What is algae and why does algae grow in your fish tank?

It is worthwhile taking some time to understand why we get algae in our aquariums in the first place. This will help understand what action can be taken to prevent its occurrence.
Algae is a plant like organism that is part of a family that includes seaweed. Algae does not have stems, roots or leaves like many other plants but does contain chlorophyll which is why it is classed as a plant. This also gives it its green appearance and is the aspect that allows it to use photosynthesis to feed. Algae can grow in filaments which is what happens with seaweed and why it has a plant-like appearance.

There are many types of algae. The most common is the green algae we see in our aquariums however there are also red and brown algae. Red algae needs to attach itself to something and is often seen on rocks or plants. Brown algae, or diatoms, can actually be good for your aquarium but can easily cause an imbalance in your tank's ecosystem.

When we understand that algae feeds through photosynthesis then we can start to understand why it grows in our tanks. Photosynthesis is the process that plants use to turn water (H2O) and sunlight (CO2) into sugars and oxygen (O2). The plant then uses the carbohydrates (sugars) as food and the oxygen is a by-product that the algae releases. So, the two main ingredients required for photosynthesis are water and sunlight. Phosphates can also play a significant part in photosynthesis as it maintains the efficiency of the chlorophyll and the effectiveness of the plant to turn water and light into the crucial carbohydrates that it requires to live. Phosphates naturally occur in aquariums as a result of uneaten food, using a carbon filter, plant and fish decay and phosphates are also present in the water itself. This is why using tap water is not advised for aquariums.

Is algae good or bad for an aquarium?

As I said before there are differing opinions regarding this.

The good bits - algae releases oxygen which increases dissolved oxygen levels in the water. Also, through photosynthesis algae extracts phosphates and other nutrients from the water. Algae can actively contribute to the nitrogen cycle by using nitrates and converting them to less harmful nitrites.

The bad bits - if left untreated algae will completely take over your tank. Not just surfaces but it can suspend in the open water too, known as algae bloom, which will make your water look green. This also heavily restricts the amount of oxygen in your water and will have a direct impact on your fish. We also generally keep fish for the visual beauty an aquarium creates. This can be quickly lost if your water looks muddy with algae. Blue-green algae (cyanobacteria) also produces toxic by-products which can be harmful to humans. This algae is quite unusual in aquariums as it takes high levels of nutrients for it to thrive. This would only happen in an aquarium that received almost no care or maintainence, which is very unlikely for most of us. This algae has the potential to wipe out any wildlife you have in your tank. This will need a strict clean up and maintenance routine to get rid of.

My own view is to keep algae at an absolute minimum however, it is for you to decide but the majority of hobbyists will agree that removing algae from your aquarium is the best way forward.

So by understanding this, we can now look at how we can reduce and prevent algae from growing in the first instance.

How do I prevent algae growing in my aquarium?

As we have seen algae requires water and sunlight to feed and grow. There are a couple of changes you can make to prevent algae taking hold and getting out of control.

Water - there is nothing we can do to reduce the water in the aquarium so let us look at the other aspects that affect algae growth.

Light - Firstly, it is highly recommended that you keep your aquarium out of direct sunlight. This will ensure the algae does not get a good dose of one of the vital ingredients of photosynthesis. What you also need to consider is the length of time you leave your aquarium lights on. Any more than 8 hours continuously is enough to feed the algae so monitoring the length of time you have the lights on can go a long way to preventing algae build up.

Overfeeding fish - fish waste and decaying food directly contribute the nutrients the algae needs to feed. Overfeeding can produce high phosphate and nitrate levels in the water which aids photosynthesis. It is therefore important that if any food is left in the tank, after waiting a short period after feeding, then you must remove the food to avoid it decaying and producing phosphates and nitrates.

Natural phosphates in the water - it is important to understand what natural phosphate levels are within your water source. Tap water tends to be quite high in phosphates due to how the water is treated before it gets to your home. Using a carefully pH balanced water to begin with will go some way to keep phosphates to a minimum. This is the minimum level of phosphates you can expect in your water. It will only increase once you have fish waste and decaying food in the mix too. A remedy is regular water changes where you take about 10% to 15% of the aquarium water out and replace with water from your natural water source. Testing kits are available for phosphate testing so it is worthwhile considering one of these to be sure of the levels.


Keep live plants - Live plants will compete with algae for the same food sources. This means any algae has got less chance of getting the required dose of light, water, and nutrients to grow. This is a bio-friendly way of preventing algae.

Keep algae eating fish - there are some species of fish that directly feed on algae. Angelfish and Tangs, as well as being beautiful to look at fish, will munch their way through algae very happily. Also, snails and crabs can be added to your aquarium both of which will eat any algae.

Have a Protein Skimmer - this will extract nutrients from the water which algae can thrive on. They do come at a cost but will prevent dissolved organic compounds(DOCs) building up which will prevent algae growth.

Good tank maintenance - regularly remove a small percentage of water, remove any early indications of algae, clean your filter and top up the water with a low phosphate water.

How do I clean algae from my fish tank?

For even the most experienced hobbyist there are occasions where algae can take hold and requires you to take direct action to remove it

Wipe surfaces - any build up on the inside of your glass is highly likely to be algae. You can use an algae brush to scrub this clean.

Vacuum gravel - algae will grow on just about any surface and this includes your gravel. Gravel vacuums are available to buy and make this an easy job. The frequency of vacuuming is one that is highly debated by hobbyists so worthwhile doing some research on how often you feel you should vacuum.

Algae eating fish - this has been mentioned already to help prevent algae but you can also introduce algae eating fish if algae is already present in your tank.

Clean decorations and ornaments - Take the decorations out of the tank if they have algae present. Make a mild bleach solution and clean the algae off using this. Rince the decorations and then you then need to neutralize the bleach. This is done by using a dechlorinating solution before the decorations can be placed back in your tank.

Overall if you spot algae in your tank the golden rule is to remove it immediately. Hopefully, the advice above will then help you determine the cause of your algae and preventative measures you can take to keep it to a minimum once you have rid your tank of any initial build up.

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