Algae (pronounced AL-jee) are simple forms of marine plant life. They’re pretty basic: they lack leaves, roots, flowers, seeds, and all the other things we normally associate with plants. The term ‘algae’ is an umbrella phrase that’s used to refer to all forms of marine life that are capable of photosynthesis (converting sunlight into energy), although some forms of algae rely entirely on external supplies of energy (in the form of protein and fish waste in the water) for food.
As far as your tropical fish tank goes, algae is definitely an unwanted visitor – it’s a real eyesore. Of course, certain levels of algae are to be expected; small amounts are inevitable wherever there’s light, nutrients, and water in combination.
However, when levels get high enough to be visible to the naked eye, you’ve got a surplus.Unless you maintain your aquarium regularly, you can pretty much count on regular growths of algae obscuring your fish, making the water smell, and generally detracting from the aesthetic appeal of your tank.
But what is it – and how do you get rid of it?
Well, it depends on the type of algae that you have, since each one needs to be treated in a specific manner. The most common forms of algae to affect tropical fish tanks are:
• brown algae
• green algae
• blue-green algae
• green water
What to do about brown algae:
Brown algae is usually the first to appear in a newly established tank. It’s pretty easy to see: it looks like cloudy brown slime growing along the sides and bottom of your aquarium, as well as clinging onto gravel, rocks, and ornaments.
Limiting the light available won’t make any difference to this type of algae, since it’s perfectly capable of growing at low-lighting levels.
Instead, you need to cut right back on the nutrients available for sustaining its growth – which means feeding your fish less. High protein levels in the tank, derived from fish food, will fuel this algae’s growth.
Even if your fish are eating all the food you give them, this doesn’t mean you’re feeding them the right amount: when it comes to food, fish are natural opportunists, which means they’ll eat everything that’s available regardless of how much you feed them. If they’re overeating, they simply excrete the undigested food – which then floats around in the tank, feeding the algae instead!
Make sure you follow the directions stringently on the fish-food package, to be certain that you’re minimizing nutrient levels appropriately.
In addition to keeping food levels down, make sure you’re maintaining your tank adequately with enough water changes and gravel and filter cleanings.
If brown algae appears in an established aquarium, you’ll need to check the phosphate and nitrate levels, as too much of either will encourage the growth of the algae.
If the problem remains ongoing, you can use algae-eaters. These are bottom-dwelling fish – such as the American-flag fish and the Siamese algae eater - which feed on algae, and are commonly stocked by pet stores and fish traders. They’ll make quick work of your brown algae problem!
What to do about green algae:
Green algae will appear in just about any tank with plenty of light. Fortunately, it’s easy to remove (it doesn’t cling to the glass too much) and most algae-eaters will consume it with gusto.
For green algae, make sure you’re minimizing the protein in the tank, as you would for brown algae. Start by cutting the fish-food back by one quarter, and pay close attention to the appearance of your fish: if their bodies become flat and thin, they’re not eating enough. They should be getting just enough food to remain slightly round-bodied.
Keep your fish tank stocked with plenty of algae-eaters, and the problem should take care of itself (although it bears repeating that a certain amount of algae, particularly green algae, is to be expected).
What to do about blue-green algae:
Blue-green algae is technically not really an algae in the true sense of the word – it’s actually a form of bacteria, called cyanobacteria, which is a type of bacteria capable of photosynthesis. Cyanobacteria is one of the oldest organisms in the world, and is thought to have been around for at least 3.5 billion years!
It looks like a slimy coating in a number of greenish-blue shades, and the wastes it releases can actually be toxic to your fish – another good reason to keep it to a bare minimum.
The good thing about blue-green algae is that it’s easy to remove manually: usually, it forms ‘sheets’ of hanging matter in the water, which can easily be scooped out.
The bad thing about it is that it’s pretty hardy: even after a thorough removal, it’ll usually have returned by the next day.
This algae is usually caused by low levels of nitrates (usually in combination with high levels of phosphate), and an imbalance of bacteria in the water.
How to get rid of this persistent eyesore:
• Block all light for a week, and siphon the dead algae out of the tank each day. Your plants will be feeling pretty sorry for themselves by the seventh day, but they should recover just fine.
• Add new bacteria after every water change. You can purchase bacteria pellets for this express purpose from your pet store and aquarium supply dealer. Ask for bacteria pellets that remove ammonia and excess protein from the water.
• Be stringent with your tank maintenance: keep everything clean, check the filter for clogging, make sure the lights are working adequately (blue-green algae needs light to survive, but good fluorescents are necessary to maintain an adequate balance of bacteria and plant life in the tank).
What to do about green water:
If the water in your tank is green, cloudy, and murky, then you have green water. This is a particular form of free-floating algae which hangs suspended in the water, giving it that characteristic opacity – in some cases, the water becomes so green that the fish are obscured.
It’s usually due to a significant excess of light (usually sunlight, as opposed to too much fluorescent), or a problem with your water quality.
To treat this problem:
• Block all sunlight from reaching your tank for several days to one week. You can do this by draping fabric over your tank, or making sure that all the curtains remain drawn in the room where your aquarium is placed. This is very effective.
• Keep your filter mesh as fine as you can: most generic filters come with pretty coarse mesh, so replace it with a fine-meshed sponge or use a diatomic filter (designed specifically to treat algal problems). Remember to check the filter regularly, or else it’ll get clogged.
General algae prevention tips:
Regular maintenance of your tank is one of the best preventative measures when it comes to algae:
• Change the water regularly
• Clean the aquarium regularly
• Use a UV filter in the tank
• Situate the tank away from direct sunlight
• Don’t overcrowd the fish
• Keep the food levels down
• Minimize aeration unless your aquarium is very well stocked: keep airstones and vents to a minimum
• Utilize your plants’ nitrate and phosphate absorbing capacity: stock your aquarium with plenty of fast-growing species like Ambulia and Egeria
Maintaining a healthy, attractive aquarium can be a pretty complex task – there’s so much to keep track of!
For smart, relevant, detailed, and easy to follow advice on keeping a professional-standard aquarium, we recommend Katy’s Tropical Fish – A Complete Guide.
It’s packed with valuable insider tips for keeping a fabulous aquarium, regardless of budget and experience – all aspects of tropical aquarium maintenance are covered, from fish health to algae problems to fish compatibility. It’s a complete owner’s manual!
However, when levels get high enough to be visible to the naked eye, you’ve got a surplus.Unless you maintain your aquarium regularly, you can pretty much count on regular growths of algae obscuring your fish, making the water smell, and generally detracting from the aesthetic appeal of your tank.
But what is it – and how do you get rid of it?
Well, it depends on the type of algae that you have, since each one needs to be treated in a specific manner. The most common forms of algae to affect tropical fish tanks are:
• brown algae
• green algae
• blue-green algae
• green water
What to do about brown algae:
Brown algae is usually the first to appear in a newly established tank. It’s pretty easy to see: it looks like cloudy brown slime growing along the sides and bottom of your aquarium, as well as clinging onto gravel, rocks, and ornaments.
Limiting the light available won’t make any difference to this type of algae, since it’s perfectly capable of growing at low-lighting levels.
Instead, you need to cut right back on the nutrients available for sustaining its growth – which means feeding your fish less. High protein levels in the tank, derived from fish food, will fuel this algae’s growth.
Even if your fish are eating all the food you give them, this doesn’t mean you’re feeding them the right amount: when it comes to food, fish are natural opportunists, which means they’ll eat everything that’s available regardless of how much you feed them. If they’re overeating, they simply excrete the undigested food – which then floats around in the tank, feeding the algae instead!
Make sure you follow the directions stringently on the fish-food package, to be certain that you’re minimizing nutrient levels appropriately.
In addition to keeping food levels down, make sure you’re maintaining your tank adequately with enough water changes and gravel and filter cleanings.
If brown algae appears in an established aquarium, you’ll need to check the phosphate and nitrate levels, as too much of either will encourage the growth of the algae.
If the problem remains ongoing, you can use algae-eaters. These are bottom-dwelling fish – such as the American-flag fish and the Siamese algae eater - which feed on algae, and are commonly stocked by pet stores and fish traders. They’ll make quick work of your brown algae problem!
What to do about green algae:
Green algae will appear in just about any tank with plenty of light. Fortunately, it’s easy to remove (it doesn’t cling to the glass too much) and most algae-eaters will consume it with gusto.
For green algae, make sure you’re minimizing the protein in the tank, as you would for brown algae. Start by cutting the fish-food back by one quarter, and pay close attention to the appearance of your fish: if their bodies become flat and thin, they’re not eating enough. They should be getting just enough food to remain slightly round-bodied.
Keep your fish tank stocked with plenty of algae-eaters, and the problem should take care of itself (although it bears repeating that a certain amount of algae, particularly green algae, is to be expected).
What to do about blue-green algae:
Blue-green algae is technically not really an algae in the true sense of the word – it’s actually a form of bacteria, called cyanobacteria, which is a type of bacteria capable of photosynthesis. Cyanobacteria is one of the oldest organisms in the world, and is thought to have been around for at least 3.5 billion years!
It looks like a slimy coating in a number of greenish-blue shades, and the wastes it releases can actually be toxic to your fish – another good reason to keep it to a bare minimum.
The good thing about blue-green algae is that it’s easy to remove manually: usually, it forms ‘sheets’ of hanging matter in the water, which can easily be scooped out.
The bad thing about it is that it’s pretty hardy: even after a thorough removal, it’ll usually have returned by the next day.
This algae is usually caused by low levels of nitrates (usually in combination with high levels of phosphate), and an imbalance of bacteria in the water.
How to get rid of this persistent eyesore:
• Block all light for a week, and siphon the dead algae out of the tank each day. Your plants will be feeling pretty sorry for themselves by the seventh day, but they should recover just fine.
• Add new bacteria after every water change. You can purchase bacteria pellets for this express purpose from your pet store and aquarium supply dealer. Ask for bacteria pellets that remove ammonia and excess protein from the water.
• Be stringent with your tank maintenance: keep everything clean, check the filter for clogging, make sure the lights are working adequately (blue-green algae needs light to survive, but good fluorescents are necessary to maintain an adequate balance of bacteria and plant life in the tank).
What to do about green water:
If the water in your tank is green, cloudy, and murky, then you have green water. This is a particular form of free-floating algae which hangs suspended in the water, giving it that characteristic opacity – in some cases, the water becomes so green that the fish are obscured.
It’s usually due to a significant excess of light (usually sunlight, as opposed to too much fluorescent), or a problem with your water quality.
To treat this problem:
• Block all sunlight from reaching your tank for several days to one week. You can do this by draping fabric over your tank, or making sure that all the curtains remain drawn in the room where your aquarium is placed. This is very effective.
• Keep your filter mesh as fine as you can: most generic filters come with pretty coarse mesh, so replace it with a fine-meshed sponge or use a diatomic filter (designed specifically to treat algal problems). Remember to check the filter regularly, or else it’ll get clogged.
General algae prevention tips:
Regular maintenance of your tank is one of the best preventative measures when it comes to algae:
• Change the water regularly
• Clean the aquarium regularly
• Use a UV filter in the tank
• Situate the tank away from direct sunlight
• Don’t overcrowd the fish
• Keep the food levels down
• Minimize aeration unless your aquarium is very well stocked: keep airstones and vents to a minimum
• Utilize your plants’ nitrate and phosphate absorbing capacity: stock your aquarium with plenty of fast-growing species like Ambulia and Egeria
Maintaining a healthy, attractive aquarium can be a pretty complex task – there’s so much to keep track of!
For smart, relevant, detailed, and easy to follow advice on keeping a professional-standard aquarium, we recommend Katy’s Tropical Fish – A Complete Guide.
It’s packed with valuable insider tips for keeping a fabulous aquarium, regardless of budget and experience – all aspects of tropical aquarium maintenance are covered, from fish health to algae problems to fish compatibility. It’s a complete owner’s manual!