10 Ways to Get Rid of Green Algae in Fish Tank

In this post, I want to talk about controlling hair algae. Because let’s face it, it’s one of the most common issues that we have as Aquarius. The presence of algae can be unsightly and gross, although it’s not usually harmful, it is something we want to get rid of.

Algae can become a serious nuisance in the aquarium. In the worst cases, they will pollute the tank and kill all your livestock and plants. Moreover, as many people (wrongly) attribute the growth of algae to excessive lighting, they are probably the single most common reason why many aquarists give up on growing aquatic plants. In truth, algae will proliferate if the lighting is too low, too bright or left on too long.

Sunlight will also cause an algal bloom. Regular water changes are essential in reducing the levels of nitrates, phosphates, sulfates, and carbonates, all of which provide food for algae. Algae are extremely resilient. Their spores are carried over long periods by air currents in the upper atmosphere. Despite being exposed to the most intense cold, heat, and radiation, the spores germinate once they encounter more favorable conditions.

Some algae can survive long periods of desiccation, so leaving an old piece of rock or wood to dry out is no guarantee of killing them. They may simply remain dormant and become active when placed in a warm aquarium.

Types of Algae

This post is primarily concerned with four types: Green Algae, Diatoms, Whip Algae, and Blue-green Algae.

Green Algae comprise several different kinds of organism. Two of the most common nuisance varieties are Chlorella, which appears as a green film on the tank glass, and Chlamydomonas (filamentous or thread algae), which festoons rocks and plants. Some of the other, “colonial” forms of green algae are beneficial, as they may be cultivated to provide green water to feed some fry.

Diatoms are usually associated with plankton in the ocean. However, they occur in freshwater as well and will multiply rapidly where there are high concentrations of nitrates and phosphates. In severe cases of infestation, they will even discolor the water, but it is more usual for them to coat rocks, gravel, etc. in brown slime.

Whip Algae use flagella (whips) to propel themselves through the water. They require very high nitrogen levels to survive, so it is rare to find them in an aquarium – if you do, then it is likely that all your livestock will already have been killed by the pollution.

Blue-green Algae, or cyanobacteria, are by far the most troublesome variety. They can swiftly coat everything in the tank in a thick slime that suffocates plants and kills fish if left unchecked. Blue-green algae are not true algae; they possess characteristics of both algae and bacteria, hence the alternative name. They will proliferate where there is a combination of bright light and water that is rich in phosphates and nitrates.

How can I prevent algae from getting into my aquarium?

In short, you can’t! Algal spores are carried in the air and float freely in water. They can be introduced with fish, on plants or rocks, or may be blown into the tank. The best you can do is to check all plants, rocks, etc. for traces of algae before introducing them into the tank and. if necessary, sterilize them.

Are there any natural methods of controlling algae?

The most obvious is to use fish that graze on algae. Depending on the Other inmates of your tank and its maturity, you might try the Siamese Algae Eater (Crossochei/us siamensis), or some of the sucker-mouth catfish – Hypostomus. Otocinclus and Farlowella species.

For newly set-up tanks, Kissing Gouramis are particularly useful, as are a couple of pairs of Swordtails or Platies (Xiphophorus spp.). Despite its name, the Algae Eater is not the most efficient fish at clearing algae and has the additional drawback of harassing your other fish.

In summary, you should not expect any of these fish to keep the whole tank Spotless; you may still have to scrape the aquarium glass. What most of them are particularly good at is cleaning the plant leaves without damaging them.

Whatever type of aquarium you have, the control of algae is a matter of striking the correct balance of light, fish stocking levels, water quality and plant growth. As long as algae can be kept under control, as in the tank pictured here, they may even help you achieve an informal, natural look in your aquarium.

Is there any easy way of removing thread algae?

There is no way to eradicate them completely. However, one of the more effective methods of keeping them down is to use one of the rough canes that support house plants.

Poke this into the center of the algal mass and twirl it between your fingers, thereby wrapping the filaments around the cane. When you pull the cane out you will remove the algae with it. Repeat as often as necessary. Doing this doesn’t get rid of the problem, but it does help to keep it under control.

Can I use an algicide to control algae?

Yes, you can, but you should only do so as a last resort. Be careful not to overdose, and always follow the manufacturer’s instructions to the letter. It is just as important to siphon out all the dead algae that tend to gather on the substrate, otherwise, they will overload the filtration system as they decompose. This, in turn, may give rise to further problems.

Here are 10 ways you can combat algae in your tank

Manual removal

Probably a little obvious, but it’s manual removal. Whether you’re using a sponge or an algae scraper, or if it’s something like hair algae, pinching it off with your fingers. Removing algae manually before doing anything else to try and prevent further growth, is really important.

The reason it’s important is that the more algae you have in your tank, the faster it’s going to replicate and make more of itself. So getting rid of as much as possible first, and then taking other preventative measures is your best course of action, to make sure it doesn’t come back.

Algae magnet cleaner for aquariums

No direct sunlight

At the beginning of setting up a tank, make sure your aquarium doesn’t get any direct sunlight. If your aquarium gets direct sunlight, the algae will grow like crazy, kind of overdrive and that’s because like all plants on our planet, algae is evolved to use the sun to grow.

So our aquarium lights they’re not quite like the Sun, they’re not as strong as the sun, the spectrum is a little off – the Sun is the Sun. And it’s going to make stuff grow like mad – and algae are one of those things. If you have problems with sunlight on your tank, get some blinds, blackout blinds, or blackout curtains, and solve that problem.

Reduce light period

What does that mean? What you can do, if you have an algae outbreak, is try to reduce the amount of time your aquarium light is on, on the aquarium. Sometimes we get really bright aquarium lights because let’s face it, they look great on the tank, it makes everything in the tank glow, and really stand out.

But what that means is, you’re probably putting a lot of light into the aquarium than you actually need, unless you have live plants. And that extra light is going to fuel algae to grow. So what you can do is make sure that your photoperiod is shorter, so the amount of light per day is less, and the algae has less of an opportunity to utilize that light to grow.

How many hours a day should Aquarium light be on?

The average aquarist is probably gonna put their tank on sometime in the morning before they go to work, and maybe sometime in the evening when they get back. That can be as long as 12 hours.

That’s a lot more than you need, most aquariums will be just fine with around 6 to 8 hours and you can even go less if the ambient room light is not pitch-black. The fish will get the idea that it’s daytime, just from the ambient room light, and that means you can save the actual aquarium light time, for the time your home to enjoy it.

So if you’re not gonna be able to enjoy it in the morning, leave the aquarium light off, and have it turn on when you get home in the evening. If you have live plants or live corals, this method will work as well, because your plants and corals are going to need X amount of light, at X amount of intensity during the day, in order to thrive. So be very careful with messing with your photoperiod if you have corals or plants.

Reduce the light intensity

A lot like reducing photoperiod, you can reduce the light intensity. This works really well with something like dimmable LEDs. In this day and age, we have access to a lot of really cool light fixtures, they get super-bright a lot of the time because we want to keep live plants or corals.

But those of us without those live plants or corals, often get these fixtures, because they make the tank look awesome. The problem is, if you leave them running full blast, that’s a ton of light, and the algae are going to use it and it’s gonna grow like mad. So what I suggest is try turning the fixture down to about 50%, that will definitely help the amount of growth you’re getting out of your algae.

It should reduce it, and therefore you will have fewer algae in the aquarium. So if you can reduce light intensity, give it a shot it’ll probably work. Just keep in mind, when you mess with the intensity of the light, if you have live plants or corals, that rely on that light, you don’t want to ever bring the light passes the threshold, where they’re going to thrive. Algae may be thriving with them, but there are other things we can do to combat the algae if you have live plants and corals, so be careful with that.

Replace fluorescent bulb before they start to burn out

If you have fluorescent lights on your tank, which a lot of us do, it’s been a staple for so many years right up until LEDs came out and things are kind of shifting that way, but a lot of us still have T5 high output for instance.

Fluorescent bulbs over their lifetime will slowly shift in the spectrum as they get closer to burning out. And a lot of us wait till they burn out before we replace them, because why would you replace them before that? – because as they shift in the spectrum, oftentimes that shift is in the favor of photosynthesis for algae, which means the algae can now use those old bulbs to grow a lot more efficiently, than when they were new, which sounds counterintuitive.

But it’s the truth, so when your bulbs are starting to get a little close to the edge, (the manufacturer usually gives you recommendations on when to replace them) you should actually replace them. Because they could be the reason that you have algae problems now, that you didn’t have before.


Just like reducing the lighting, whether it’s through photoperiod or intensity, we can go one step further and do what’s referred to as a blackout on the aquarium, where we turn off the lights for a few days, usually 48 hours to 72 hours and then cover the tank, whether it’s with black plastic garbage, bags or really thick blankets. Something that will not allow any light to get into the tank, cover it up completely and just let it simmer.

Can algae die without light?

Obviously, you still want to feed your fish and make sure everything’s going great with the rest of it, but the complete lack of lighting will really mess up the algae and prevent it from being able to grow any further. It’ll also actually kill off quite a bit of algae. Algae don’t do well if it doesn’t get light for a prolonged period of time.

More complex organisms like plants and corals, can do just fine with 48 hours of absolutely no light, it’ll mess up their circadian rhythm a little bit, however, they’re not going to perish from it, but the algae will. Just keep in mind if you do have live plants and corals, 48 hours is the max and you don’t want to do that more than once every two weeks.

Clean up crew

You can get a cleanup crew to deal with your algae. That can consist of things like snails, shrimps, for saltwater you could be looking at things like sea hares, which are essentially sea slugs and crabs as well, like emerald crabs.

Using a clean-up crew to help deal with algae in the aquarium, is one of the most effective ways that you can stop algae from getting out of hand. A lot of the time you’ll add a cleanup crew when you start your tank, whether it’s saltwater or freshwater, and then they’ll always be there to help keep algae at bay.

Assassin snail

What clean up crew eats hair algae

In freshwater tanks, it’s a little less prevalent, and people don’t usually get a cleanup crew right away. They wait until there’s a problem and then get one. I advocate, as soon as you start experiencing any algae in the tank, right near the beginning, you can add something like nerite snails to help deal with it. You can also add Amano shrimp or Cherry shrimp as long as
you don’t have fish that are gonna pick on them, to also deal with things like hair algae.

They work great for planted tanks, where you’re gonna get a lot of extra algae in a freshwater setting, and then for saltwater like I mentioned sea hares, emerald crabs, trochus snails – are one of my absolute favorite along with turbo snails, they’re definitely an asset, and I think every tank can benefit from having a cleanup crew.


What fish eat algae?

There are all kinds of fish that are gonna help reduce the algae in your aquarium. One of the most commonly known ones is plecos (Plecostomus). People really like to get plecos, usually common plecos to try to combat algae I will say though common plecos get very large, and a much better idea would be a bushy nose or Ancistrus pleco, they stay much smaller, and they actually do a really good job of eating algae, especially while they’re young.

You can also get Siamese algae eaters, flying foxes, you can also get Chinese algae eaters. They’re really gonna help keep the glass clean. Catfish which are tiny will do a great job of keeping algae off of plant leaves. For saltwater fish – all kinds of tangs are great algae eaters, rabbitfish are also fantastic algae eaters.

Don’t overfeed your fish

This is something that we can all fall victim to because it’s really easy to feed your fish all the time or feed them away too much. Because feeding our fish is one of the easiest ways for us to interact with them.

If you feed too much, they’re gonna poop a lot more and if you put too much food in that once during those over feedings, some of that food is gonna just go to the bottom and break down, which is not good, it’s gonna lead to having higher levels of phosphate and nitrate. So the more you feed, can end up turning into the more algae you have. Being very careful about how much you feed and keeping it within reason, is really gonna help keep algae at bay.

Reduce phosphate, nitrates, and silicates

If you’ve already been overfeeding your fish like we just talked about, those nutrients are already there. So we got to get rid of them, and even if you don’t overfeed your fish sometimes those nutrients can build up anyways, just because certain types of food may have more phosphates or nitrates.

Sometimes we lose fish in the tank, unfortunately, and we never recover the body and they decompose. What you can do to reduce the amount of nutrients in the tank, is use certain types of filter media like ferric oxide or Chemi-pure elite.

How do I get rid of excess phosphate and silicate in my aquarium?

There are all kinds of phosphate, nitrate, and silicate reducing media. You can put in your filter, to pull out the nutrients that the algae are using that are already there, and then dispose of it. you can also do the most obvious thing, which is water changes. A lot of the dirt that builds up in the gravel, you’re gonna want to take that out too, because over time it’s just gonna break down, further and further, and it’s gonna fuel algae.

So while you’re doing your water change, get your gravel siphon and clean everything up, get it out of there and you’re gonna help reduce the amount of algae that are in the aquarium.