How to get rid of algae in an aquarium?

For any aquarium owner, algae is the most dreaded problem. It's not only unsightly, but it can also block your fish from moving around.

For an overview, check out our reference guide: Algae in aquariums: cleaning and rebalancing the tank.

There are simple ways to prevent algae in aquariums and get rid of it. Read our mini-guide to find out how.

Algae is a "basic" plant that can make its own food via photosynthesis, using light. These aquarium algae are generally very small, although they are part of a huge group ranging from these tiny single-celled algae that cause green water to much more developed algae. 

Algae were among the very first life forms on earth and are now present on all continents, both land and sea. They can tolerate extremely variable conditions, ranging from freezing to boiling, from fresh water to saltier than the sea, and have adapted to live and inhabit practically everywhere on earth. In our aquariums, it generally appears as a green coating on the glass and decor, but it can also take many other forms.

Where does algae come from?

Algae can be introduced into an aquarium on the leaves of plants or in the water from fish bags, but even in aquariums that have been set up and are completely sterile, without plants, fish water, or other forms of life, algae can still start to grow.

Algae spores can also be airborne and are everywhere we humans are. Whether it's a cold water, tropical, or marine aquarium, or even a barrel of reverse osmosis water, if light can reach it, algae will grow.

How to stop algae?

You will not be able to completely stop algae growth in your aquarium unless it is kept in total darkness at all times. However, there are many ways to control it. 

A. Cut thelighting

If your aquarium contains live plants or corals, they will need the lights to be on for at least eight hours a day, but no more than twelve. If you have nothing that really needs light to grow and you have bad algae, try turning the lights on only when you are in front of the tank, looking at it.

Optimizing aquarium lighting

Fish do not care about ambient light (many species prefer low light), so your fish will not suffer and you will consequently get less algae. For planted and reef aquariums, make sure not to exceed 12 hours of light per day and not to use more light than necessary. Some LED lights can be dimmed, faded, and faded, and directed specifically at where the plant or coral is, which means less light is wasted and less light spreads on the front glass, causing harmful algae. 

B. Add algae eaters

Mother nature has many allies that will graze and consume algae for you. For fresh water and salt water, an army of snails, shrimp, and algae-eating fish can be deployed to graze the algae for you, helping to control it, penetrate inaccessible places, and nibble it 24 hours a day. . Many species also need algae in their diet. 

Add algae eaters when the first shoots of algae become visible and they will help to control it. Algae eaters will not eat all types of algae (more on this below) and will also ensure that their diet is supplemented with species-specific foods, such as shrimp food, or algae wafers or tablets.

Exclusive algae-based foods will also contain essential vitamins for shrimp and algae-grazing fish. If the algae are completely consumed, the algae eaters will be hungry, so they will need regular feeding, just like your other fish. 

C. Solutions to limit algae

In addition to needing light, algae also need nutrients to thrive. In the aquarium, algae nutrients can appear in the form of nitrates and phosphates. Nitrate is the byproduct of biological filtration and accumulates, and phosphates can come from fish food, fish waste, and tap water.

Control nitrates and phosphates with removal resins for nitrates and phosphates and you can fight algae. Plants naturally absorb nitrate and phosphate as food, and some aquatic plant growers and aquascapers actually add nitrate and phosphate to their planted tanks, but that's for another article.

Nitrate and phosphate-free water can also be created using a reverse osmosis unit, and ideally a deionizer, to ensure that the changed water is free of nitrate and phosphate. 

D. Perform water changes

Water changes are a very simple way to control harmful algae. As mentioned above, nutrient levels can be lowered by water changes, but this also gives you an excuse to physically remove the algae during maintenance. As part of your weekly routine, wipe the algae off the glass, scrub the plant leaves and decor, then siphon the algae scratches with a gravel vacuum.

Clean your filter sponge in the dirty water bucket of the tank, then filter maintenance, tank maintenance, and algae removal can be done at once. Changing the water helps physically reduce the amount of algae spores in the aquarium, and the old tank water can be reused to water the plants in your house or garden. 

When algae is not algae

One of the most harmful types of algae in the aquarium, slime algae, is not algae at all. Belonging to the genus Cyanobacteria, as its scientific name indicates, Slime algae is actually a bacterium, not algae at all, but it grows and behaves in the same way, smothering surfaces and only thriving in tanks with light and nutrients.

The downside of this harmful bacterium is that algae eaters have no desire to eat it. In fact, they won't touch it, and it can even be slightly toxic to some forms of life. It is generally blue/green in fresh water tanks and red in marine tanks.

The good news is that cyanobacteria can be treated like conventional algae, by scraping and brushing them off surfaces, then physically siphoning them. Regular maintenance is essential with Cyano, as well as many water changes and a strong water flow to avoid dead spots that this slime prefers. 

Three complementary levers for a balanced aquarium

• Controlled lighting: avoid direct sunlight on the tank and program a regular lighting duration.
• Lots of fast-growing plants: they consume the available nutrients and leave less room for algae.
• A reasonable population: the more fish there are, the more nitrogenous waste there is in the water; adapt the number of fish to the volume and filtration.

Algae recedes on its own when these three parameters are rebalanced. Avoid aggressive chemical treatments: they also weaken the plants and can restart the problem.